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Date: Mon, 14 Dec 2020 20:22:14 -0000
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] locking/core for v5.11-rc1
Linus,
please pull the latest locking/core branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-core-2020-12-14
up to: cb262935a166: seqlock: kernel-doc: Specify when preemption is automatically altered
A moderate set of locking updates:
- A few extensions to the rwsem API and support for opportunistic
spinning and lock stealing
- lockdep selftest improvements
- Documentation updates
- Cleanups and small fixes all over the place
Thanks,
tglx
------------------>
Ahmed S. Darwish (3):
Documentation: seqlock: s/LOCKTYPE/LOCKNAME/g
seqlock: Prefix internal seqcount_t-only macros with a "do_"
seqlock: kernel-doc: Specify when preemption is automatically altered
Arnd Bergmann (1):
seqlock: avoid -Wshadow warnings
Boqun Feng (1):
lockdep/selftest: Add spin_nest_lock test
Eric W. Biederman (2):
rwsem: Implement down_read_killable_nested
rwsem: Implement down_read_interruptible
Lukas Bulwahn (1):
futex: Remove unused empty compat_exit_robust_list()
Mauro Carvalho Chehab (2):
completion: Drop init_completion define
refcount: Fix a kernel-doc markup
Peter Zijlstra (7):
lockdep/selftests: Fix PROVE_RAW_LOCK_NESTING
seqlock: Rename __seqprop() users
atomic: Delete obsolete documentation
atomic: Update MAINTAINERS
locking/rwsem: Better collate rwsem_read_trylock()
locking/rwsem: Introduce rwsem_write_trylock()
locking/rwsem: Fold __down_{read,write}*()
Waiman Long (4):
locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath()
locking/rwsem: Prevent potential lock starvation
locking/rwsem: Enable reader optimistic lock stealing
locking/rwsem: Remove reader optimistic spinning
Documentation/core-api/atomic_ops.rst | 664 ----------------------------------
Documentation/locking/seqlock.rst | 21 +-
MAINTAINERS | 2 +
include/linux/completion.h | 5 +-
include/linux/refcount.h | 2 +-
include/linux/rwsem.h | 3 +
include/linux/seqlock.h | 121 ++++---
kernel/futex.c | 2 -
kernel/locking/lock_events_list.h | 6 +-
kernel/locking/rwsem.c | 383 +++++++-------------
lib/locking-selftest.c | 51 ++-
11 files changed, 253 insertions(+), 1007 deletions(-)
delete mode 100644 Documentation/core-api/atomic_ops.rst
diff --git a/Documentation/core-api/atomic_ops.rst b/Documentation/core-api/atomic_ops.rst
deleted file mode 100644
index 724583453e1f..000000000000
--- a/Documentation/core-api/atomic_ops.rst
+++ /dev/null
@@ -1,664 +0,0 @@
-=======================================================
-Semantics and Behavior of Atomic and Bitmask Operations
-=======================================================
-
-:Author: David S. Miller
-
-This document is intended to serve as a guide to Linux port
-maintainers on how to implement atomic counter, bitops, and spinlock
-interfaces properly.
-
-Atomic Type And Operations
-==========================
-
-The atomic_t type should be defined as a signed integer and
-the atomic_long_t type as a signed long integer. Also, they should
-be made opaque such that any kind of cast to a normal C integer type
-will fail. Something like the following should suffice::
-
- typedef struct { int counter; } atomic_t;
- typedef struct { long counter; } atomic_long_t;
-
-Historically, counter has been declared volatile. This is now discouraged.
-See :ref:`Documentation/process/volatile-considered-harmful.rst
-<volatile_considered_harmful>` for the complete rationale.
-
-local_t is very similar to atomic_t. If the counter is per CPU and only
-updated by one CPU, local_t is probably more appropriate. Please see
-:ref:`Documentation/core-api/local_ops.rst <local_ops>` for the semantics of
-local_t.
-
-The first operations to implement for atomic_t's are the initializers and
-plain writes. ::
-
- #define ATOMIC_INIT(i) { (i) }
- #define atomic_set(v, i) ((v)->counter = (i))
-
-The first macro is used in definitions, such as::
-
- static atomic_t my_counter = ATOMIC_INIT(1);
-
-The initializer is atomic in that the return values of the atomic operations
-are guaranteed to be correct reflecting the initialized value if the
-initializer is used before runtime. If the initializer is used at runtime, a
-proper implicit or explicit read memory barrier is needed before reading the
-value with atomic_read from another thread.
-
-As with all of the ``atomic_`` interfaces, replace the leading ``atomic_``
-with ``atomic_long_`` to operate on atomic_long_t.
-
-The second interface can be used at runtime, as in::
-
- struct foo { atomic_t counter; };
- ...
-
- struct foo *k;
-
- k = kmalloc(sizeof(*k), GFP_KERNEL);
- if (!k)
- return -ENOMEM;
- atomic_set(&k->counter, 0);
-
-The setting is atomic in that the return values of the atomic operations by
-all threads are guaranteed to be correct reflecting either the value that has
-been set with this operation or set with another operation. A proper implicit
-or explicit memory barrier is needed before the value set with the operation
-is guaranteed to be readable with atomic_read from another thread.
-
-Next, we have::
-
- #define atomic_read(v) ((v)->counter)
-
-which simply reads the counter value currently visible to the calling thread.
-The read is atomic in that the return value is guaranteed to be one of the
-values initialized or modified with the interface operations if a proper
-implicit or explicit memory barrier is used after possible runtime
-initialization by any other thread and the value is modified only with the
-interface operations. atomic_read does not guarantee that the runtime
-initialization by any other thread is visible yet, so the user of the
-interface must take care of that with a proper implicit or explicit memory
-barrier.
-
-.. warning::
-
- ``atomic_read()`` and ``atomic_set()`` DO NOT IMPLY BARRIERS!
-
- Some architectures may choose to use the volatile keyword, barriers, or
- inline assembly to guarantee some degree of immediacy for atomic_read()
- and atomic_set(). This is not uniformly guaranteed, and may change in
- the future, so all users of atomic_t should treat atomic_read() and
- atomic_set() as simple C statements that may be reordered or optimized
- away entirely by the compiler or processor, and explicitly invoke the
- appropriate compiler and/or memory barrier for each use case. Failure
- to do so will result in code that may suddenly break when used with
- different architectures or compiler optimizations, or even changes in
- unrelated code which changes how the compiler optimizes the section
- accessing atomic_t variables.
-
-Properly aligned pointers, longs, ints, and chars (and unsigned
-equivalents) may be atomically loaded from and stored to in the same
-sense as described for atomic_read() and atomic_set(). The READ_ONCE()
-and WRITE_ONCE() macros should be used to prevent the compiler from using
-optimizations that might otherwise optimize accesses out of existence on
-the one hand, or that might create unsolicited accesses on the other.
-
-For example consider the following code::
-
- while (a > 0)
- do_something();
-
-If the compiler can prove that do_something() does not store to the
-variable a, then the compiler is within its rights transforming this to
-the following::
-
- if (a > 0)
- for (;;)
- do_something();
-
-If you don't want the compiler to do this (and you probably don't), then
-you should use something like the following::
-
- while (READ_ONCE(a) > 0)
- do_something();
-
-Alternatively, you could place a barrier() call in the loop.
-
-For another example, consider the following code::
-
- tmp_a = a;
- do_something_with(tmp_a);
- do_something_else_with(tmp_a);
-
-If the compiler can prove that do_something_with() does not store to the
-variable a, then the compiler is within its rights to manufacture an
-additional load as follows::
-
- tmp_a = a;
- do_something_with(tmp_a);
- tmp_a = a;
- do_something_else_with(tmp_a);
-
-This could fatally confuse your code if it expected the same value
-to be passed to do_something_with() and do_something_else_with().
-
-The compiler would be likely to manufacture this additional load if
-do_something_with() was an inline function that made very heavy use
-of registers: reloading from variable a could save a flush to the
-stack and later reload. To prevent the compiler from attacking your
-code in this manner, write the following::
-
- tmp_a = READ_ONCE(a);
- do_something_with(tmp_a);
- do_something_else_with(tmp_a);
-
-For a final example, consider the following code, assuming that the
-variable a is set at boot time before the second CPU is brought online
-and never changed later, so that memory barriers are not needed::
-
- if (a)
- b = 9;
- else
- b = 42;
-
-The compiler is within its rights to manufacture an additional store
-by transforming the above code into the following::
-
- b = 42;
- if (a)
- b = 9;
-
-This could come as a fatal surprise to other code running concurrently
-that expected b to never have the value 42 if a was zero. To prevent
-the compiler from doing this, write something like::
-
- if (a)
- WRITE_ONCE(b, 9);
- else
- WRITE_ONCE(b, 42);
-
-Don't even -think- about doing this without proper use of memory barriers,
-locks, or atomic operations if variable a can change at runtime!
-
-.. warning::
-
- ``READ_ONCE()`` OR ``WRITE_ONCE()`` DO NOT IMPLY A BARRIER!
-
-Now, we move onto the atomic operation interfaces typically implemented with
-the help of assembly code. ::
-
- void atomic_add(int i, atomic_t *v);
- void atomic_sub(int i, atomic_t *v);
- void atomic_inc(atomic_t *v);
- void atomic_dec(atomic_t *v);
-
-These four routines add and subtract integral values to/from the given
-atomic_t value. The first two routines pass explicit integers by
-which to make the adjustment, whereas the latter two use an implicit
-adjustment value of "1".
-
-One very important aspect of these two routines is that they DO NOT
-require any explicit memory barriers. They need only perform the
-atomic_t counter update in an SMP safe manner.
-
-Next, we have::
-
- int atomic_inc_return(atomic_t *v);
- int atomic_dec_return(atomic_t *v);
-
-These routines add 1 and subtract 1, respectively, from the given
-atomic_t and return the new counter value after the operation is
-performed.
-
-Unlike the above routines, it is required that these primitives
-include explicit memory barriers that are performed before and after
-the operation. It must be done such that all memory operations before
-and after the atomic operation calls are strongly ordered with respect
-to the atomic operation itself.
-
-For example, it should behave as if a smp_mb() call existed both
-before and after the atomic operation.
-
-If the atomic instructions used in an implementation provide explicit
-memory barrier semantics which satisfy the above requirements, that is
-fine as well.
-
-Let's move on::
-
- int atomic_add_return(int i, atomic_t *v);
- int atomic_sub_return(int i, atomic_t *v);
-
-These behave just like atomic_{inc,dec}_return() except that an
-explicit counter adjustment is given instead of the implicit "1".
-This means that like atomic_{inc,dec}_return(), the memory barrier
-semantics are required.
-
-Next::
-
- int atomic_inc_and_test(atomic_t *v);
- int atomic_dec_and_test(atomic_t *v);
-
-These two routines increment and decrement by 1, respectively, the
-given atomic counter. They return a boolean indicating whether the
-resulting counter value was zero or not.
-
-Again, these primitives provide explicit memory barrier semantics around
-the atomic operation::
-
- int atomic_sub_and_test(int i, atomic_t *v);
-
-This is identical to atomic_dec_and_test() except that an explicit
-decrement is given instead of the implicit "1". This primitive must
-provide explicit memory barrier semantics around the operation::
-
- int atomic_add_negative(int i, atomic_t *v);
-
-The given increment is added to the given atomic counter value. A boolean
-is return which indicates whether the resulting counter value is negative.
-This primitive must provide explicit memory barrier semantics around
-the operation.
-
-Then::
-
- int atomic_xchg(atomic_t *v, int new);
-
-This performs an atomic exchange operation on the atomic variable v, setting
-the given new value. It returns the old value that the atomic variable v had
-just before the operation.
-
-atomic_xchg must provide explicit memory barriers around the operation. ::
-
- int atomic_cmpxchg(atomic_t *v, int old, int new);
-
-This performs an atomic compare exchange operation on the atomic value v,
-with the given old and new values. Like all atomic_xxx operations,
-atomic_cmpxchg will only satisfy its atomicity semantics as long as all
-other accesses of \*v are performed through atomic_xxx operations.
-
-atomic_cmpxchg must provide explicit memory barriers around the operation,
-although if the comparison fails then no memory ordering guarantees are
-required.
-
-The semantics for atomic_cmpxchg are the same as those defined for 'cas'
-below.
-
-Finally::
-
- int atomic_add_unless(atomic_t *v, int a, int u);
-
-If the atomic value v is not equal to u, this function adds a to v, and
-returns non zero. If v is equal to u then it returns zero. This is done as
-an atomic operation.
-
-atomic_add_unless must provide explicit memory barriers around the
-operation unless it fails (returns 0).
-
-atomic_inc_not_zero, equivalent to atomic_add_unless(v, 1, 0)
-
-
-If a caller requires memory barrier semantics around an atomic_t
-operation which does not return a value, a set of interfaces are
-defined which accomplish this::
-
- void smp_mb__before_atomic(void);
- void smp_mb__after_atomic(void);
-
-Preceding a non-value-returning read-modify-write atomic operation with
-smp_mb__before_atomic() and following it with smp_mb__after_atomic()
-provides the same full ordering that is provided by value-returning
-read-modify-write atomic operations.
-
-For example, smp_mb__before_atomic() can be used like so::
-
- obj->dead = 1;
- smp_mb__before_atomic();
- atomic_dec(&obj->ref_count);
-
-It makes sure that all memory operations preceding the atomic_dec()
-call are strongly ordered with respect to the atomic counter
-operation. In the above example, it guarantees that the assignment of
-"1" to obj->dead will be globally visible to other cpus before the
-atomic counter decrement.
-
-Without the explicit smp_mb__before_atomic() call, the
-implementation could legally allow the atomic counter update visible
-to other cpus before the "obj->dead = 1;" assignment.
-
-A missing memory barrier in the cases where they are required by the
-atomic_t implementation above can have disastrous results. Here is
-an example, which follows a pattern occurring frequently in the Linux
-kernel. It is the use of atomic counters to implement reference
-counting, and it works such that once the counter falls to zero it can
-be guaranteed that no other entity can be accessing the object::
-
- static void obj_list_add(struct obj *obj, struct list_head *head)
- {
- obj->active = 1;
- list_add(&obj->list, head);
- }
-
- static void obj_list_del(struct obj *obj)
- {
- list_del(&obj->list);
- obj->active = 0;
- }
-
- static void obj_destroy(struct obj *obj)
- {
- BUG_ON(obj->active);
- kfree(obj);
- }
-
- struct obj *obj_list_peek(struct list_head *head)
- {
- if (!list_empty(head)) {
- struct obj *obj;
-
- obj = list_entry(head->next, struct obj, list);
- atomic_inc(&obj->refcnt);
- return obj;
- }
- return NULL;
- }
-
- void obj_poke(void)
- {
- struct obj *obj;
-
- spin_lock(&global_list_lock);
- obj = obj_list_peek(&global_list);
- spin_unlock(&global_list_lock);
-
- if (obj) {
- obj->ops->poke(obj);
- if (atomic_dec_and_test(&obj->refcnt))
- obj_destroy(obj);
- }
- }
-
- void obj_timeout(struct obj *obj)
- {
- spin_lock(&global_list_lock);
- obj_list_del(obj);
- spin_unlock(&global_list_lock);
-
- if (atomic_dec_and_test(&obj->refcnt))
- obj_destroy(obj);
- }
-
-.. note::
-
- This is a simplification of the ARP queue management in the generic
- neighbour discover code of the networking. Olaf Kirch found a bug wrt.
- memory barriers in kfree_skb() that exposed the atomic_t memory barrier
- requirements quite clearly.
-
-Given the above scheme, it must be the case that the obj->active
-update done by the obj list deletion be visible to other processors
-before the atomic counter decrement is performed.
-
-Otherwise, the counter could fall to zero, yet obj->active would still
-be set, thus triggering the assertion in obj_destroy(). The error
-sequence looks like this::
-
- cpu 0 cpu 1
- obj_poke() obj_timeout()
- obj = obj_list_peek();
- ... gains ref to obj, refcnt=2
- obj_list_del(obj);
- obj->active = 0 ...
- ... visibility delayed ...
- atomic_dec_and_test()
- ... refcnt drops to 1 ...
- atomic_dec_and_test()
- ... refcount drops to 0 ...
- obj_destroy()
- BUG() triggers since obj->active
- still seen as one
- obj->active update visibility occurs
-
-With the memory barrier semantics required of the atomic_t operations
-which return values, the above sequence of memory visibility can never
-happen. Specifically, in the above case the atomic_dec_and_test()
-counter decrement would not become globally visible until the
-obj->active update does.
-
-As a historical note, 32-bit Sparc used to only allow usage of
-24-bits of its atomic_t type. This was because it used 8 bits
-as a spinlock for SMP safety. Sparc32 lacked a "compare and swap"
-type instruction. However, 32-bit Sparc has since been moved over
-to a "hash table of spinlocks" scheme, that allows the full 32-bit
-counter to be realized. Essentially, an array of spinlocks are
-indexed into based upon the address of the atomic_t being operated
-on, and that lock protects the atomic operation. Parisc uses the
-same scheme.
-
-Another note is that the atomic_t operations returning values are
-extremely slow on an old 386.
-
-
-Atomic Bitmask
-==============
-
-We will now cover the atomic bitmask operations. You will find that
-their SMP and memory barrier semantics are similar in shape and scope
-to the atomic_t ops above.
-
-Native atomic bit operations are defined to operate on objects aligned
-to the size of an "unsigned long" C data type, and are least of that
-size. The endianness of the bits within each "unsigned long" are the
-native endianness of the cpu. ::
-
- void set_bit(unsigned long nr, volatile unsigned long *addr);
- void clear_bit(unsigned long nr, volatile unsigned long *addr);
- void change_bit(unsigned long nr, volatile unsigned long *addr);
-
-These routines set, clear, and change, respectively, the bit number
-indicated by "nr" on the bit mask pointed to by "ADDR".
-
-They must execute atomically, yet there are no implicit memory barrier
-semantics required of these interfaces. ::
-
- int test_and_set_bit(unsigned long nr, volatile unsigned long *addr);
- int test_and_clear_bit(unsigned long nr, volatile unsigned long *addr);
- int test_and_change_bit(unsigned long nr, volatile unsigned long *addr);
-
-Like the above, except that these routines return a boolean which
-indicates whether the changed bit was set _BEFORE_ the atomic bit
-operation.
-
-
-.. warning::
- It is incredibly important that the value be a boolean, ie. "0" or "1".
- Do not try to be fancy and save a few instructions by declaring the
- above to return "long" and just returning something like "old_val &
- mask" because that will not work.
-
-For one thing, this return value gets truncated to int in many code
-paths using these interfaces, so on 64-bit if the bit is set in the
-upper 32-bits then testers will never see that.
-
-One great example of where this problem crops up are the thread_info
-flag operations. Routines such as test_and_set_ti_thread_flag() chop
-the return value into an int. There are other places where things
-like this occur as well.
-
-These routines, like the atomic_t counter operations returning values,
-must provide explicit memory barrier semantics around their execution.
-All memory operations before the atomic bit operation call must be
-made visible globally before the atomic bit operation is made visible.
-Likewise, the atomic bit operation must be visible globally before any
-subsequent memory operation is made visible. For example::
-
- obj->dead = 1;
- if (test_and_set_bit(0, &obj->flags))
- /* ... */;
- obj->killed = 1;
-
-The implementation of test_and_set_bit() must guarantee that
-"obj->dead = 1;" is visible to cpus before the atomic memory operation
-done by test_and_set_bit() becomes visible. Likewise, the atomic
-memory operation done by test_and_set_bit() must become visible before
-"obj->killed = 1;" is visible.
-
-Finally there is the basic operation::
-
- int test_bit(unsigned long nr, __const__ volatile unsigned long *addr);
-
-Which returns a boolean indicating if bit "nr" is set in the bitmask
-pointed to by "addr".
-
-If explicit memory barriers are required around {set,clear}_bit() (which do
-not return a value, and thus does not need to provide memory barrier
-semantics), two interfaces are provided::
-
- void smp_mb__before_atomic(void);
- void smp_mb__after_atomic(void);
-
-They are used as follows, and are akin to their atomic_t operation
-brothers::
-
- /* All memory operations before this call will
- * be globally visible before the clear_bit().
- */
- smp_mb__before_atomic();
- clear_bit( ... );
-
- /* The clear_bit() will be visible before all
- * subsequent memory operations.
- */
- smp_mb__after_atomic();
-
-There are two special bitops with lock barrier semantics (acquire/release,
-same as spinlocks). These operate in the same way as their non-_lock/unlock
-postfixed variants, except that they are to provide acquire/release semantics,
-respectively. This means they can be used for bit_spin_trylock and
-bit_spin_unlock type operations without specifying any more barriers. ::
-
- int test_and_set_bit_lock(unsigned long nr, unsigned long *addr);
- void clear_bit_unlock(unsigned long nr, unsigned long *addr);
- void __clear_bit_unlock(unsigned long nr, unsigned long *addr);
-
-The __clear_bit_unlock version is non-atomic, however it still implements
-unlock barrier semantics. This can be useful if the lock itself is protecting
-the other bits in the word.
-
-Finally, there are non-atomic versions of the bitmask operations
-provided. They are used in contexts where some other higher-level SMP
-locking scheme is being used to protect the bitmask, and thus less
-expensive non-atomic operations may be used in the implementation.
-They have names similar to the above bitmask operation interfaces,
-except that two underscores are prefixed to the interface name. ::
-
- void __set_bit(unsigned long nr, volatile unsigned long *addr);
- void __clear_bit(unsigned long nr, volatile unsigned long *addr);
- void __change_bit(unsigned long nr, volatile unsigned long *addr);
- int __test_and_set_bit(unsigned long nr, volatile unsigned long *addr);
- int __test_and_clear_bit(unsigned long nr, volatile unsigned long *addr);
- int __test_and_change_bit(unsigned long nr, volatile unsigned long *addr);
-
-These non-atomic variants also do not require any special memory
-barrier semantics.
-
-The routines xchg() and cmpxchg() must provide the same exact
-memory-barrier semantics as the atomic and bit operations returning
-values.
-
-.. note::
-
- If someone wants to use xchg(), cmpxchg() and their variants,
- linux/atomic.h should be included rather than asm/cmpxchg.h, unless the
- code is in arch/* and can take care of itself.
-
-Spinlocks and rwlocks have memory barrier expectations as well.
-The rule to follow is simple:
-
-1) When acquiring a lock, the implementation must make it globally
- visible before any subsequent memory operation.
-
-2) When releasing a lock, the implementation must make it such that
- all previous memory operations are globally visible before the
- lock release.
-
-Which finally brings us to _atomic_dec_and_lock(). There is an
-architecture-neutral version implemented in lib/dec_and_lock.c,
-but most platforms will wish to optimize this in assembler. ::
-
- int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
-
-Atomically decrement the given counter, and if will drop to zero
-atomically acquire the given spinlock and perform the decrement
-of the counter to zero. If it does not drop to zero, do nothing
-with the spinlock.
-
-It is actually pretty simple to get the memory barrier correct.
-Simply satisfy the spinlock grab requirements, which is make
-sure the spinlock operation is globally visible before any
-subsequent memory operation.
-
-We can demonstrate this operation more clearly if we define
-an abstract atomic operation::
-
- long cas(long *mem, long old, long new);
-
-"cas" stands for "compare and swap". It atomically:
-
-1) Compares "old" with the value currently at "mem".
-2) If they are equal, "new" is written to "mem".
-3) Regardless, the current value at "mem" is returned.
-
-As an example usage, here is what an atomic counter update
-might look like::
-
- void example_atomic_inc(long *counter)
- {
- long old, new, ret;
-
- while (1) {
- old = *counter;
- new = old + 1;
-
- ret = cas(counter, old, new);
- if (ret == old)
- break;
- }
- }
-
-Let's use cas() in order to build a pseudo-C atomic_dec_and_lock()::
-
- int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
- {
- long old, new, ret;
- int went_to_zero;
-
- went_to_zero = 0;
- while (1) {
- old = atomic_read(atomic);
- new = old - 1;
- if (new == 0) {
- went_to_zero = 1;
- spin_lock(lock);
- }
- ret = cas(atomic, old, new);
- if (ret == old)
- break;
- if (went_to_zero) {
- spin_unlock(lock);
- went_to_zero = 0;
- }
- }
-
- return went_to_zero;
- }
-
-Now, as far as memory barriers go, as long as spin_lock()
-strictly orders all subsequent memory operations (including
-the cas()) with respect to itself, things will be fine.
-
-Said another way, _atomic_dec_and_lock() must guarantee that
-a counter dropping to zero is never made visible before the
-spinlock being acquired.
-
-.. note::
-
- Note that this also means that for the case where the counter is not
- dropping to zero, there are no memory ordering requirements.
diff --git a/Documentation/locking/seqlock.rst b/Documentation/locking/seqlock.rst
index a334b584f2b3..64405e5da63e 100644
--- a/Documentation/locking/seqlock.rst
+++ b/Documentation/locking/seqlock.rst
@@ -89,7 +89,7 @@ Read path::
.. _seqcount_locktype_t:
-Sequence counters with associated locks (``seqcount_LOCKTYPE_t``)
+Sequence counters with associated locks (``seqcount_LOCKNAME_t``)
-----------------------------------------------------------------
As discussed at :ref:`seqcount_t`, sequence count write side critical
@@ -115,27 +115,26 @@ The following sequence counters with associated locks are defined:
- ``seqcount_mutex_t``
- ``seqcount_ww_mutex_t``
-The plain seqcount read and write APIs branch out to the specific
-seqcount_LOCKTYPE_t implementation at compile-time. This avoids kernel
-API explosion per each new seqcount LOCKTYPE.
+The sequence counter read and write APIs can take either a plain
+seqcount_t or any of the seqcount_LOCKNAME_t variants above.
-Initialization (replace "LOCKTYPE" with one of the supported locks)::
+Initialization (replace "LOCKNAME" with one of the supported locks)::
/* dynamic */
- seqcount_LOCKTYPE_t foo_seqcount;
- seqcount_LOCKTYPE_init(&foo_seqcount, &lock);
+ seqcount_LOCKNAME_t foo_seqcount;
+ seqcount_LOCKNAME_init(&foo_seqcount, &lock);
/* static */
- static seqcount_LOCKTYPE_t foo_seqcount =
- SEQCNT_LOCKTYPE_ZERO(foo_seqcount, &lock);
+ static seqcount_LOCKNAME_t foo_seqcount =
+ SEQCNT_LOCKNAME_ZERO(foo_seqcount, &lock);
/* C99 struct init */
struct {
- .seq = SEQCNT_LOCKTYPE_ZERO(foo.seq, &lock),
+ .seq = SEQCNT_LOCKNAME_ZERO(foo.seq, &lock),
} foo;
Write path: same as in :ref:`seqcount_t`, while running from a context
-with the associated LOCKTYPE lock acquired.
+with the associated write serialization lock acquired.
Read path: same as in :ref:`seqcount_t`.
diff --git a/MAINTAINERS b/MAINTAINERS
index 2daa6ee673f7..4ba045a0ad25 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2973,6 +2973,8 @@ L: linux-kernel@...r.kernel.org
S: Maintained
F: arch/*/include/asm/atomic*.h
F: include/*/atomic*.h
+F: include/linux/refcount.h
+F: Documentation/atomic_*.txt
F: scripts/atomic/
ATTO EXPRESSSAS SAS/SATA RAID SCSI DRIVER
diff --git a/include/linux/completion.h b/include/linux/completion.h
index bf8e77001f18..51d9ab079629 100644
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -28,8 +28,7 @@ struct completion {
struct swait_queue_head wait;
};
-#define init_completion_map(x, m) __init_completion(x)
-#define init_completion(x) __init_completion(x)
+#define init_completion_map(x, m) init_completion(x)
static inline void complete_acquire(struct completion *x) {}
static inline void complete_release(struct completion *x) {}
@@ -82,7 +81,7 @@ static inline void complete_release(struct completion *x) {}
* This inline function will initialize a dynamically created completion
* structure.
*/
-static inline void __init_completion(struct completion *x)
+static inline void init_completion(struct completion *x)
{
x->done = 0;
init_swait_queue_head(&x->wait);
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 497990c69b0b..b8a6e387f8f9 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -101,7 +101,7 @@
struct mutex;
/**
- * struct refcount_t - variant of atomic_t specialized for reference counts
+ * typedef refcount_t - variant of atomic_t specialized for reference counts
* @refs: atomic_t counter field
*
* The counter saturates at REFCOUNT_SATURATED and will not move once
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 25e3fde85617..4c715be48717 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -123,6 +123,7 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem)
* lock for reading
*/
extern void down_read(struct rw_semaphore *sem);
+extern int __must_check down_read_interruptible(struct rw_semaphore *sem);
extern int __must_check down_read_killable(struct rw_semaphore *sem);
/*
@@ -171,6 +172,7 @@ extern void downgrade_write(struct rw_semaphore *sem);
* See Documentation/locking/lockdep-design.rst for more details.)
*/
extern void down_read_nested(struct rw_semaphore *sem, int subclass);
+extern int __must_check down_read_killable_nested(struct rw_semaphore *sem, int subclass);
extern void down_write_nested(struct rw_semaphore *sem, int subclass);
extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock);
@@ -191,6 +193,7 @@ extern void down_read_non_owner(struct rw_semaphore *sem);
extern void up_read_non_owner(struct rw_semaphore *sem);
#else
# define down_read_nested(sem, subclass) down_read(sem)
+# define down_read_killable_nested(sem, subclass) down_read_killable(sem)
# define down_write_nest_lock(sem, nest_lock) down_write(sem)
# define down_write_nested(sem, subclass) down_write(sem)
# define down_write_killable_nested(sem, subclass) down_write_killable(sem)
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index cbfc78b92b65..2f7bb92b4c9e 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -307,10 +307,10 @@ SEQCOUNT_LOCKNAME(ww_mutex, struct ww_mutex, true, &s->lock->base, ww_mu
__seqprop_case((s), mutex, prop), \
__seqprop_case((s), ww_mutex, prop))
-#define __seqcount_ptr(s) __seqprop(s, ptr)
-#define __seqcount_sequence(s) __seqprop(s, sequence)
-#define __seqcount_lock_preemptible(s) __seqprop(s, preemptible)
-#define __seqcount_assert_lock_held(s) __seqprop(s, assert)
+#define seqprop_ptr(s) __seqprop(s, ptr)
+#define seqprop_sequence(s) __seqprop(s, sequence)
+#define seqprop_preemptible(s) __seqprop(s, preemptible)
+#define seqprop_assert(s) __seqprop(s, assert)
/**
* __read_seqcount_begin() - begin a seqcount_t read section w/o barrier
@@ -328,13 +328,13 @@ SEQCOUNT_LOCKNAME(ww_mutex, struct ww_mutex, true, &s->lock->base, ww_mu
*/
#define __read_seqcount_begin(s) \
({ \
- unsigned seq; \
+ unsigned __seq; \
\
- while ((seq = __seqcount_sequence(s)) & 1) \
+ while ((__seq = seqprop_sequence(s)) & 1) \
cpu_relax(); \
\
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX); \
- seq; \
+ __seq; \
})
/**
@@ -345,10 +345,10 @@ SEQCOUNT_LOCKNAME(ww_mutex, struct ww_mutex, true, &s->lock->base, ww_mu
*/
#define raw_read_seqcount_begin(s) \
({ \
- unsigned seq = __read_seqcount_begin(s); \
+ unsigned _seq = __read_seqcount_begin(s); \
\
smp_rmb(); \
- seq; \
+ _seq; \
})
/**
@@ -359,7 +359,7 @@ SEQCOUNT_LOCKNAME(ww_mutex, struct ww_mutex, true, &s->lock->base, ww_mu
*/
#define read_seqcount_begin(s) \
({ \
- seqcount_lockdep_reader_access(__seqcount_ptr(s)); \
+ seqcount_lockdep_reader_access(seqprop_ptr(s)); \
raw_read_seqcount_begin(s); \
})
@@ -376,11 +376,11 @@ SEQCOUNT_LOCKNAME(ww_mutex, struct ww_mutex, true, &s->lock->base, ww_mu
*/
#define raw_read_seqcount(s) \
({ \
- unsigned seq = __seqcount_sequence(s); \
+ unsigned __seq = seqprop_sequence(s); \
\
smp_rmb(); \
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX); \
- seq; \
+ __seq; \
})
/**
@@ -425,9 +425,9 @@ SEQCOUNT_LOCKNAME(ww_mutex, struct ww_mutex, true, &s->lock->base, ww_mu
* Return: true if a read section retry is required, else false
*/
#define __read_seqcount_retry(s, start) \
- __read_seqcount_t_retry(__seqcount_ptr(s), start)
+ do___read_seqcount_retry(seqprop_ptr(s), start)
-static inline int __read_seqcount_t_retry(const seqcount_t *s, unsigned start)
+static inline int do___read_seqcount_retry(const seqcount_t *s, unsigned start)
{
kcsan_atomic_next(0);
return unlikely(READ_ONCE(s->sequence) != start);
@@ -445,27 +445,29 @@ static inline int __read_seqcount_t_retry(const seqcount_t *s, unsigned start)
* Return: true if a read section retry is required, else false
*/
#define read_seqcount_retry(s, start) \
- read_seqcount_t_retry(__seqcount_ptr(s), start)
+ do_read_seqcount_retry(seqprop_ptr(s), start)
-static inline int read_seqcount_t_retry(const seqcount_t *s, unsigned start)
+static inline int do_read_seqcount_retry(const seqcount_t *s, unsigned start)
{
smp_rmb();
- return __read_seqcount_t_retry(s, start);
+ return do___read_seqcount_retry(s, start);
}
/**
* raw_write_seqcount_begin() - start a seqcount_t write section w/o lockdep
* @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ *
+ * Context: check write_seqcount_begin()
*/
#define raw_write_seqcount_begin(s) \
do { \
- if (__seqcount_lock_preemptible(s)) \
+ if (seqprop_preemptible(s)) \
preempt_disable(); \
\
- raw_write_seqcount_t_begin(__seqcount_ptr(s)); \
+ do_raw_write_seqcount_begin(seqprop_ptr(s)); \
} while (0)
-static inline void raw_write_seqcount_t_begin(seqcount_t *s)
+static inline void do_raw_write_seqcount_begin(seqcount_t *s)
{
kcsan_nestable_atomic_begin();
s->sequence++;
@@ -475,16 +477,18 @@ static inline void raw_write_seqcount_t_begin(seqcount_t *s)
/**
* raw_write_seqcount_end() - end a seqcount_t write section w/o lockdep
* @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ *
+ * Context: check write_seqcount_end()
*/
#define raw_write_seqcount_end(s) \
do { \
- raw_write_seqcount_t_end(__seqcount_ptr(s)); \
+ do_raw_write_seqcount_end(seqprop_ptr(s)); \
\
- if (__seqcount_lock_preemptible(s)) \
+ if (seqprop_preemptible(s)) \
preempt_enable(); \
} while (0)
-static inline void raw_write_seqcount_t_end(seqcount_t *s)
+static inline void do_raw_write_seqcount_end(seqcount_t *s)
{
smp_wmb();
s->sequence++;
@@ -498,20 +502,21 @@ static inline void raw_write_seqcount_t_end(seqcount_t *s)
* @subclass: lockdep nesting level
*
* See Documentation/locking/lockdep-design.rst
+ * Context: check write_seqcount_begin()
*/
#define write_seqcount_begin_nested(s, subclass) \
do { \
- __seqcount_assert_lock_held(s); \
+ seqprop_assert(s); \
\
- if (__seqcount_lock_preemptible(s)) \
+ if (seqprop_preemptible(s)) \
preempt_disable(); \
\
- write_seqcount_t_begin_nested(__seqcount_ptr(s), subclass); \
+ do_write_seqcount_begin_nested(seqprop_ptr(s), subclass); \
} while (0)
-static inline void write_seqcount_t_begin_nested(seqcount_t *s, int subclass)
+static inline void do_write_seqcount_begin_nested(seqcount_t *s, int subclass)
{
- raw_write_seqcount_t_begin(s);
+ do_raw_write_seqcount_begin(s);
seqcount_acquire(&s->dep_map, subclass, 0, _RET_IP_);
}
@@ -519,46 +524,46 @@ static inline void write_seqcount_t_begin_nested(seqcount_t *s, int subclass)
* write_seqcount_begin() - start a seqcount_t write side critical section
* @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
*
- * write_seqcount_begin opens a write side critical section of the given
- * seqcount_t.
- *
- * Context: seqcount_t write side critical sections must be serialized and
- * non-preemptible. If readers can be invoked from hardirq or softirq
+ * Context: sequence counter write side sections must be serialized and
+ * non-preemptible. Preemption will be automatically disabled if and
+ * only if the seqcount write serialization lock is associated, and
+ * preemptible. If readers can be invoked from hardirq or softirq
* context, interrupts or bottom halves must be respectively disabled.
*/
#define write_seqcount_begin(s) \
do { \
- __seqcount_assert_lock_held(s); \
+ seqprop_assert(s); \
\
- if (__seqcount_lock_preemptible(s)) \
+ if (seqprop_preemptible(s)) \
preempt_disable(); \
\
- write_seqcount_t_begin(__seqcount_ptr(s)); \
+ do_write_seqcount_begin(seqprop_ptr(s)); \
} while (0)
-static inline void write_seqcount_t_begin(seqcount_t *s)
+static inline void do_write_seqcount_begin(seqcount_t *s)
{
- write_seqcount_t_begin_nested(s, 0);
+ do_write_seqcount_begin_nested(s, 0);
}
/**
* write_seqcount_end() - end a seqcount_t write side critical section
* @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
*
- * The write section must've been opened with write_seqcount_begin().
+ * Context: Preemption will be automatically re-enabled if and only if
+ * the seqcount write serialization lock is associated, and preemptible.
*/
#define write_seqcount_end(s) \
do { \
- write_seqcount_t_end(__seqcount_ptr(s)); \
+ do_write_seqcount_end(seqprop_ptr(s)); \
\
- if (__seqcount_lock_preemptible(s)) \
+ if (seqprop_preemptible(s)) \
preempt_enable(); \
} while (0)
-static inline void write_seqcount_t_end(seqcount_t *s)
+static inline void do_write_seqcount_end(seqcount_t *s)
{
seqcount_release(&s->dep_map, _RET_IP_);
- raw_write_seqcount_t_end(s);
+ do_raw_write_seqcount_end(s);
}
/**
@@ -603,9 +608,9 @@ static inline void write_seqcount_t_end(seqcount_t *s)
* }
*/
#define raw_write_seqcount_barrier(s) \
- raw_write_seqcount_t_barrier(__seqcount_ptr(s))
+ do_raw_write_seqcount_barrier(seqprop_ptr(s))
-static inline void raw_write_seqcount_t_barrier(seqcount_t *s)
+static inline void do_raw_write_seqcount_barrier(seqcount_t *s)
{
kcsan_nestable_atomic_begin();
s->sequence++;
@@ -623,9 +628,9 @@ static inline void raw_write_seqcount_t_barrier(seqcount_t *s)
* will complete successfully and see data older than this.
*/
#define write_seqcount_invalidate(s) \
- write_seqcount_t_invalidate(__seqcount_ptr(s))
+ do_write_seqcount_invalidate(seqprop_ptr(s))
-static inline void write_seqcount_t_invalidate(seqcount_t *s)
+static inline void do_write_seqcount_invalidate(seqcount_t *s)
{
smp_wmb();
kcsan_nestable_atomic_begin();
@@ -865,9 +870,9 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
}
/*
- * For all seqlock_t write side functions, use write_seqcount_*t*_begin()
- * instead of the generic write_seqcount_begin(). This way, no redundant
- * lockdep_assert_held() checks are added.
+ * For all seqlock_t write side functions, use the the internal
+ * do_write_seqcount_begin() instead of generic write_seqcount_begin().
+ * This way, no redundant lockdep_assert_held() checks are added.
*/
/**
@@ -886,7 +891,7 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
static inline void write_seqlock(seqlock_t *sl)
{
spin_lock(&sl->lock);
- write_seqcount_t_begin(&sl->seqcount.seqcount);
+ do_write_seqcount_begin(&sl->seqcount.seqcount);
}
/**
@@ -898,7 +903,7 @@ static inline void write_seqlock(seqlock_t *sl)
*/
static inline void write_sequnlock(seqlock_t *sl)
{
- write_seqcount_t_end(&sl->seqcount.seqcount);
+ do_write_seqcount_end(&sl->seqcount.seqcount);
spin_unlock(&sl->lock);
}
@@ -912,7 +917,7 @@ static inline void write_sequnlock(seqlock_t *sl)
static inline void write_seqlock_bh(seqlock_t *sl)
{
spin_lock_bh(&sl->lock);
- write_seqcount_t_begin(&sl->seqcount.seqcount);
+ do_write_seqcount_begin(&sl->seqcount.seqcount);
}
/**
@@ -925,7 +930,7 @@ static inline void write_seqlock_bh(seqlock_t *sl)
*/
static inline void write_sequnlock_bh(seqlock_t *sl)
{
- write_seqcount_t_end(&sl->seqcount.seqcount);
+ do_write_seqcount_end(&sl->seqcount.seqcount);
spin_unlock_bh(&sl->lock);
}
@@ -939,7 +944,7 @@ static inline void write_sequnlock_bh(seqlock_t *sl)
static inline void write_seqlock_irq(seqlock_t *sl)
{
spin_lock_irq(&sl->lock);
- write_seqcount_t_begin(&sl->seqcount.seqcount);
+ do_write_seqcount_begin(&sl->seqcount.seqcount);
}
/**
@@ -951,7 +956,7 @@ static inline void write_seqlock_irq(seqlock_t *sl)
*/
static inline void write_sequnlock_irq(seqlock_t *sl)
{
- write_seqcount_t_end(&sl->seqcount.seqcount);
+ do_write_seqcount_end(&sl->seqcount.seqcount);
spin_unlock_irq(&sl->lock);
}
@@ -960,7 +965,7 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl)
unsigned long flags;
spin_lock_irqsave(&sl->lock, flags);
- write_seqcount_t_begin(&sl->seqcount.seqcount);
+ do_write_seqcount_begin(&sl->seqcount.seqcount);
return flags;
}
@@ -989,7 +994,7 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl)
static inline void
write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags)
{
- write_seqcount_t_end(&sl->seqcount.seqcount);
+ do_write_seqcount_end(&sl->seqcount.seqcount);
spin_unlock_irqrestore(&sl->lock, flags);
}
diff --git a/kernel/futex.c b/kernel/futex.c
index 00259c7e288e..c47d1015d759 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -310,8 +310,6 @@ static inline bool should_fail_futex(bool fshared)
#ifdef CONFIG_COMPAT
static void compat_exit_robust_list(struct task_struct *curr);
-#else
-static inline void compat_exit_robust_list(struct task_struct *curr) { }
#endif
/*
diff --git a/kernel/locking/lock_events_list.h b/kernel/locking/lock_events_list.h
index 239039d0ce21..97fb6f3f840a 100644
--- a/kernel/locking/lock_events_list.h
+++ b/kernel/locking/lock_events_list.h
@@ -56,13 +56,11 @@ LOCK_EVENT(rwsem_sleep_reader) /* # of reader sleeps */
LOCK_EVENT(rwsem_sleep_writer) /* # of writer sleeps */
LOCK_EVENT(rwsem_wake_reader) /* # of reader wakeups */
LOCK_EVENT(rwsem_wake_writer) /* # of writer wakeups */
-LOCK_EVENT(rwsem_opt_rlock) /* # of opt-acquired read locks */
-LOCK_EVENT(rwsem_opt_wlock) /* # of opt-acquired write locks */
+LOCK_EVENT(rwsem_opt_lock) /* # of opt-acquired write locks */
LOCK_EVENT(rwsem_opt_fail) /* # of failed optspins */
LOCK_EVENT(rwsem_opt_nospin) /* # of disabled optspins */
-LOCK_EVENT(rwsem_opt_norspin) /* # of disabled reader-only optspins */
-LOCK_EVENT(rwsem_opt_rlock2) /* # of opt-acquired 2ndary read locks */
LOCK_EVENT(rwsem_rlock) /* # of read locks acquired */
+LOCK_EVENT(rwsem_rlock_steal) /* # of read locks by lock stealing */
LOCK_EVENT(rwsem_rlock_fast) /* # of fast read locks acquired */
LOCK_EVENT(rwsem_rlock_fail) /* # of failed read lock acquisitions */
LOCK_EVENT(rwsem_rlock_handoff) /* # of read lock handoffs */
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index f11b9bd3431d..ba67600c7b2c 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -31,19 +31,13 @@
#include "lock_events.h"
/*
- * The least significant 3 bits of the owner value has the following
+ * The least significant 2 bits of the owner value has the following
* meanings when set.
* - Bit 0: RWSEM_READER_OWNED - The rwsem is owned by readers
- * - Bit 1: RWSEM_RD_NONSPINNABLE - Readers cannot spin on this lock.
- * - Bit 2: RWSEM_WR_NONSPINNABLE - Writers cannot spin on this lock.
+ * - Bit 1: RWSEM_NONSPINNABLE - Cannot spin on a reader-owned lock
*
- * When the rwsem is either owned by an anonymous writer, or it is
- * reader-owned, but a spinning writer has timed out, both nonspinnable
- * bits will be set to disable optimistic spinning by readers and writers.
- * In the later case, the last unlocking reader should then check the
- * writer nonspinnable bit and clear it only to give writers preference
- * to acquire the lock via optimistic spinning, but not readers. Similar
- * action is also done in the reader slowpath.
+ * When the rwsem is reader-owned and a spinning writer has timed out,
+ * the nonspinnable bit will be set to disable optimistic spinning.
* When a writer acquires a rwsem, it puts its task_struct pointer
* into the owner field. It is cleared after an unlock.
@@ -59,46 +53,14 @@
* is involved. Ideally we would like to track all the readers that own
* a rwsem, but the overhead is simply too big.
*
- * Reader optimistic spinning is helpful when the reader critical section
- * is short and there aren't that many readers around. It makes readers
- * relatively more preferred than writers. When a writer times out spinning
- * on a reader-owned lock and set the nospinnable bits, there are two main
- * reasons for that.
- *
- * 1) The reader critical section is long, perhaps the task sleeps after
- * acquiring the read lock.
- * 2) There are just too many readers contending the lock causing it to
- * take a while to service all of them.
- *
- * In the former case, long reader critical section will impede the progress
- * of writers which is usually more important for system performance. In
- * the later case, reader optimistic spinning tends to make the reader
- * groups that contain readers that acquire the lock together smaller
- * leading to more of them. That may hurt performance in some cases. In
- * other words, the setting of nonspinnable bits indicates that reader
- * optimistic spinning may not be helpful for those workloads that cause
- * it.
- *
- * Therefore, any writers that had observed the setting of the writer
- * nonspinnable bit for a given rwsem after they fail to acquire the lock
- * via optimistic spinning will set the reader nonspinnable bit once they
- * acquire the write lock. Similarly, readers that observe the setting
- * of reader nonspinnable bit at slowpath entry will set the reader
- * nonspinnable bits when they acquire the read lock via the wakeup path.
- *
- * Once the reader nonspinnable bit is on, it will only be reset when
- * a writer is able to acquire the rwsem in the fast path or somehow a
- * reader or writer in the slowpath doesn't observe the nonspinable bit.
- *
- * This is to discourage reader optmistic spinning on that particular
- * rwsem and make writers more preferred. This adaptive disabling of reader
- * optimistic spinning will alleviate the negative side effect of this
- * feature.
+ * A fast path reader optimistic lock stealing is supported when the rwsem
+ * is previously owned by a writer and the following conditions are met:
+ * - OSQ is empty
+ * - rwsem is not currently writer owned
+ * - the handoff isn't set.
*/
#define RWSEM_READER_OWNED (1UL << 0)
-#define RWSEM_RD_NONSPINNABLE (1UL << 1)
-#define RWSEM_WR_NONSPINNABLE (1UL << 2)
-#define RWSEM_NONSPINNABLE (RWSEM_RD_NONSPINNABLE | RWSEM_WR_NONSPINNABLE)
+#define RWSEM_NONSPINNABLE (1UL << 1)
#define RWSEM_OWNER_FLAGS_MASK (RWSEM_READER_OWNED | RWSEM_NONSPINNABLE)
#ifdef CONFIG_DEBUG_RWSEMS
@@ -203,7 +165,7 @@ static inline void __rwsem_set_reader_owned(struct rw_semaphore *sem,
struct task_struct *owner)
{
unsigned long val = (unsigned long)owner | RWSEM_READER_OWNED |
- (atomic_long_read(&sem->owner) & RWSEM_RD_NONSPINNABLE);
+ (atomic_long_read(&sem->owner) & RWSEM_NONSPINNABLE);
atomic_long_set(&sem->owner, val);
}
@@ -270,12 +232,31 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
owner | RWSEM_NONSPINNABLE));
}
-static inline bool rwsem_read_trylock(struct rw_semaphore *sem)
+static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
{
- long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
- if (WARN_ON_ONCE(cnt < 0))
+ *cntp = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
+
+ if (WARN_ON_ONCE(*cntp < 0))
rwsem_set_nonspinnable(sem);
- return !(cnt & RWSEM_READ_FAILED_MASK);
+
+ if (!(*cntp & RWSEM_READ_FAILED_MASK)) {
+ rwsem_set_reader_owned(sem);
+ return true;
+ }
+
+ return false;
+}
+
+static inline bool rwsem_write_trylock(struct rw_semaphore *sem)
+{
+ long tmp = RWSEM_UNLOCKED_VALUE;
+
+ if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, RWSEM_WRITER_LOCKED)) {
+ rwsem_set_owner(sem);
+ return true;
+ }
+
+ return false;
}
/*
@@ -353,7 +334,6 @@ struct rwsem_waiter {
struct task_struct *task;
enum rwsem_waiter_type type;
unsigned long timeout;
- unsigned long last_rowner;
};
#define rwsem_first_waiter(sem) \
list_first_entry(&sem->wait_list, struct rwsem_waiter, list)
@@ -467,10 +447,6 @@ static void rwsem_mark_wake(struct rw_semaphore *sem,
* the reader is copied over.
*/
owner = waiter->task;
- if (waiter->last_rowner & RWSEM_RD_NONSPINNABLE) {
- owner = (void *)((unsigned long)owner | RWSEM_RD_NONSPINNABLE);
- lockevent_inc(rwsem_opt_norspin);
- }
__rwsem_set_reader_owned(sem, owner);
}
@@ -601,30 +577,6 @@ static inline bool rwsem_try_write_lock(struct rw_semaphore *sem,
}
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
-/*
- * Try to acquire read lock before the reader is put on wait queue.
- * Lock acquisition isn't allowed if the rwsem is locked or a writer handoff
- * is ongoing.
- */
-static inline bool rwsem_try_read_lock_unqueued(struct rw_semaphore *sem)
-{
- long count = atomic_long_read(&sem->count);
-
- if (count & (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))
- return false;
-
- count = atomic_long_fetch_add_acquire(RWSEM_READER_BIAS, &sem->count);
- if (!(count & (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) {
- rwsem_set_reader_owned(sem);
- lockevent_inc(rwsem_opt_rlock);
- return true;
- }
-
- /* Back out the change */
- atomic_long_add(-RWSEM_READER_BIAS, &sem->count);
- return false;
-}
-
/*
* Try to acquire write lock before the writer has been put on wait queue.
*/
@@ -636,7 +588,7 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
if (atomic_long_try_cmpxchg_acquire(&sem->count, &count,
count | RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
- lockevent_inc(rwsem_opt_wlock);
+ lockevent_inc(rwsem_opt_lock);
return true;
}
}
@@ -652,8 +604,7 @@ static inline bool owner_on_cpu(struct task_struct *owner)
return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
}
-static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
- unsigned long nonspinnable)
+static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
{
struct task_struct *owner;
unsigned long flags;
@@ -670,7 +621,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
/*
* Don't check the read-owner as the entry may be stale.
*/
- if ((flags & nonspinnable) ||
+ if ((flags & RWSEM_NONSPINNABLE) ||
(owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner)))
ret = false;
rcu_read_unlock();
@@ -700,9 +651,9 @@ enum owner_state {
#define OWNER_SPINNABLE (OWNER_NULL | OWNER_WRITER | OWNER_READER)
static inline enum owner_state
-rwsem_owner_state(struct task_struct *owner, unsigned long flags, unsigned long nonspinnable)
+rwsem_owner_state(struct task_struct *owner, unsigned long flags)
{
- if (flags & nonspinnable)
+ if (flags & RWSEM_NONSPINNABLE)
return OWNER_NONSPINNABLE;
if (flags & RWSEM_READER_OWNED)
@@ -712,14 +663,14 @@ rwsem_owner_state(struct task_struct *owner, unsigned long flags, unsigned long
}
static noinline enum owner_state
-rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
+rwsem_spin_on_owner(struct rw_semaphore *sem)
{
struct task_struct *new, *owner;
unsigned long flags, new_flags;
enum owner_state state;
owner = rwsem_owner_flags(sem, &flags);
- state = rwsem_owner_state(owner, flags, nonspinnable);
+ state = rwsem_owner_state(owner, flags);
if (state != OWNER_WRITER)
return state;
@@ -733,7 +684,7 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
*/
new = rwsem_owner_flags(sem, &new_flags);
if ((new != owner) || (new_flags != flags)) {
- state = rwsem_owner_state(new, new_flags, nonspinnable);
+ state = rwsem_owner_state(new, new_flags);
break;
}
@@ -782,14 +733,12 @@ static inline u64 rwsem_rspin_threshold(struct rw_semaphore *sem)
return sched_clock() + delta;
}
-static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
+static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
{
bool taken = false;
int prev_owner_state = OWNER_NULL;
int loop = 0;
u64 rspin_threshold = 0;
- unsigned long nonspinnable = wlock ? RWSEM_WR_NONSPINNABLE
- : RWSEM_RD_NONSPINNABLE;
preempt_disable();
@@ -806,15 +755,14 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
for (;;) {
enum owner_state owner_state;
- owner_state = rwsem_spin_on_owner(sem, nonspinnable);
+ owner_state = rwsem_spin_on_owner(sem);
if (!(owner_state & OWNER_SPINNABLE))
break;
/*
* Try to acquire the lock
*/
- taken = wlock ? rwsem_try_write_lock_unqueued(sem)
- : rwsem_try_read_lock_unqueued(sem);
+ taken = rwsem_try_write_lock_unqueued(sem);
if (taken)
break;
@@ -822,7 +770,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
/*
* Time-based reader-owned rwsem optimistic spinning
*/
- if (wlock && (owner_state == OWNER_READER)) {
+ if (owner_state == OWNER_READER) {
/*
* Re-initialize rspin_threshold every time when
* the owner state changes from non-reader to reader.
@@ -831,7 +779,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
* the beginning of the 2nd reader phase.
*/
if (prev_owner_state != OWNER_READER) {
- if (rwsem_test_oflags(sem, nonspinnable))
+ if (rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))
break;
rspin_threshold = rwsem_rspin_threshold(sem);
loop = 0;
@@ -907,78 +855,30 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
}
/*
- * Clear the owner's RWSEM_WR_NONSPINNABLE bit if it is set. This should
+ * Clear the owner's RWSEM_NONSPINNABLE bit if it is set. This should
* only be called when the reader count reaches 0.
- *
- * This give writers better chance to acquire the rwsem first before
- * readers when the rwsem was being held by readers for a relatively long
- * period of time. Race can happen that an optimistic spinner may have
- * just stolen the rwsem and set the owner, but just clearing the
- * RWSEM_WR_NONSPINNABLE bit will do no harm anyway.
*/
-static inline void clear_wr_nonspinnable(struct rw_semaphore *sem)
+static inline void clear_nonspinnable(struct rw_semaphore *sem)
{
- if (rwsem_test_oflags(sem, RWSEM_WR_NONSPINNABLE))
- atomic_long_andnot(RWSEM_WR_NONSPINNABLE, &sem->owner);
+ if (rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))
+ atomic_long_andnot(RWSEM_NONSPINNABLE, &sem->owner);
}
-/*
- * This function is called when the reader fails to acquire the lock via
- * optimistic spinning. In this case we will still attempt to do a trylock
- * when comparing the rwsem state right now with the state when entering
- * the slowpath indicates that the reader is still in a valid reader phase.
- * This happens when the following conditions are true:
- *
- * 1) The lock is currently reader owned, and
- * 2) The lock is previously not reader-owned or the last read owner changes.
- *
- * In the former case, we have transitioned from a writer phase to a
- * reader-phase while spinning. In the latter case, it means the reader
- * phase hasn't ended when we entered the optimistic spinning loop. In
- * both cases, the reader is eligible to acquire the lock. This is the
- * secondary path where a read lock is acquired optimistically.
- *
- * The reader non-spinnable bit wasn't set at time of entry or it will
- * not be here at all.
- */
-static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem,
- unsigned long last_rowner)
-{
- unsigned long owner = atomic_long_read(&sem->owner);
-
- if (!(owner & RWSEM_READER_OWNED))
- return false;
-
- if (((owner ^ last_rowner) & ~RWSEM_OWNER_FLAGS_MASK) &&
- rwsem_try_read_lock_unqueued(sem)) {
- lockevent_inc(rwsem_opt_rlock2);
- lockevent_add(rwsem_opt_fail, -1);
- return true;
- }
- return false;
-}
#else
-static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
- unsigned long nonspinnable)
+static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
{
return false;
}
-static inline bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
+static inline bool rwsem_optimistic_spin(struct rw_semaphore *sem)
{
return false;
}
-static inline void clear_wr_nonspinnable(struct rw_semaphore *sem) { }
-
-static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem,
- unsigned long last_rowner)
-{
- return false;
-}
+static inline void clear_nonspinnable(struct rw_semaphore *sem) { }
static inline int
-rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
+rwsem_spin_on_owner(struct rw_semaphore *sem)
{
return 0;
}
@@ -989,36 +889,35 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
* Wait for the read lock to be granted
*/
static struct rw_semaphore __sched *
-rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
+rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state)
{
- long count, adjustment = -RWSEM_READER_BIAS;
+ long adjustment = -RWSEM_READER_BIAS;
+ long rcnt = (count >> RWSEM_READER_SHIFT);
struct rwsem_waiter waiter;
DEFINE_WAKE_Q(wake_q);
bool wake = false;
/*
- * Save the current read-owner of rwsem, if available, and the
- * reader nonspinnable bit.
+ * To prevent a constant stream of readers from starving a sleeping
+ * waiter, don't attempt optimistic lock stealing if the lock is
+ * currently owned by readers.
*/
- waiter.last_rowner = atomic_long_read(&sem->owner);
- if (!(waiter.last_rowner & RWSEM_READER_OWNED))
- waiter.last_rowner &= RWSEM_RD_NONSPINNABLE;
-
- if (!rwsem_can_spin_on_owner(sem, RWSEM_RD_NONSPINNABLE))
+ if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) &&
+ (rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))
goto queue;
/*
- * Undo read bias from down_read() and do optimistic spinning.
+ * Reader optimistic lock stealing.
*/
- atomic_long_add(-RWSEM_READER_BIAS, &sem->count);
- adjustment = 0;
- if (rwsem_optimistic_spin(sem, false)) {
- /* rwsem_optimistic_spin() implies ACQUIRE on success */
+ if (!(count & (RWSEM_WRITER_LOCKED | RWSEM_FLAG_HANDOFF))) {
+ rwsem_set_reader_owned(sem);
+ lockevent_inc(rwsem_rlock_steal);
+
/*
- * Wake up other readers in the wait list if the front
- * waiter is a reader.
+ * Wake up other readers in the wait queue if it is
+ * the first reader.
*/
- if ((atomic_long_read(&sem->count) & RWSEM_FLAG_WAITERS)) {
+ if ((rcnt == 1) && (count & RWSEM_FLAG_WAITERS)) {
raw_spin_lock_irq(&sem->wait_lock);
if (!list_empty(&sem->wait_list))
rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED,
@@ -1027,9 +926,6 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
wake_up_q(&wake_q);
}
return sem;
- } else if (rwsem_reader_phase_trylock(sem, waiter.last_rowner)) {
- /* rwsem_reader_phase_trylock() implies ACQUIRE on success */
- return sem;
}
queue:
@@ -1045,7 +941,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
* exit the slowpath and return immediately as its
* RWSEM_READER_BIAS has already been set in the count.
*/
- if (adjustment && !(atomic_long_read(&sem->count) &
+ if (!(atomic_long_read(&sem->count) &
(RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) {
/* Provide lock ACQUIRE */
smp_acquire__after_ctrl_dep();
@@ -1059,10 +955,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
list_add_tail(&waiter.list, &sem->wait_list);
/* we're now waiting on the lock, but no longer actively locking */
- if (adjustment)
- count = atomic_long_add_return(adjustment, &sem->count);
- else
- count = atomic_long_read(&sem->count);
+ count = atomic_long_add_return(adjustment, &sem->count);
/*
* If there are no active locks, wake the front queued process(es).
@@ -1071,7 +964,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
* wake our own waiter to join the existing active readers !
*/
if (!(count & RWSEM_LOCK_MASK)) {
- clear_wr_nonspinnable(sem);
+ clear_nonspinnable(sem);
wake = true;
}
if (wake || (!(count & RWSEM_WRITER_MASK) &&
@@ -1116,19 +1009,6 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
return ERR_PTR(-EINTR);
}
-/*
- * This function is called by the a write lock owner. So the owner value
- * won't get changed by others.
- */
-static inline void rwsem_disable_reader_optspin(struct rw_semaphore *sem,
- bool disable)
-{
- if (unlikely(disable)) {
- atomic_long_or(RWSEM_RD_NONSPINNABLE, &sem->owner);
- lockevent_inc(rwsem_opt_norspin);
- }
-}
-
/*
* Wait until we successfully acquire the write lock
*/
@@ -1136,26 +1016,17 @@ static struct rw_semaphore *
rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
{
long count;
- bool disable_rspin;
enum writer_wait_state wstate;
struct rwsem_waiter waiter;
struct rw_semaphore *ret = sem;
DEFINE_WAKE_Q(wake_q);
/* do optimistic spinning and steal lock if possible */
- if (rwsem_can_spin_on_owner(sem, RWSEM_WR_NONSPINNABLE) &&
- rwsem_optimistic_spin(sem, true)) {
+ if (rwsem_can_spin_on_owner(sem) && rwsem_optimistic_spin(sem)) {
/* rwsem_optimistic_spin() implies ACQUIRE on success */
return sem;
}
- /*
- * Disable reader optimistic spinning for this rwsem after
- * acquiring the write lock when the setting of the nonspinnable
- * bits are observed.
- */
- disable_rspin = atomic_long_read(&sem->owner) & RWSEM_NONSPINNABLE;
-
/*
* Optimistic spinning failed, proceed to the slowpath
* and block until we can acquire the sem.
@@ -1224,7 +1095,7 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
* without sleeping.
*/
if (wstate == WRITER_HANDOFF &&
- rwsem_spin_on_owner(sem, RWSEM_NONSPINNABLE) == OWNER_NULL)
+ rwsem_spin_on_owner(sem) == OWNER_NULL)
goto trylock_again;
/* Block until there are no active lockers. */
@@ -1266,7 +1137,6 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
}
__set_current_state(TASK_RUNNING);
list_del(&waiter.list);
- rwsem_disable_reader_optspin(sem, disable_rspin);
raw_spin_unlock_irq(&sem->wait_lock);
lockevent_inc(rwsem_wlock);
@@ -1335,26 +1205,31 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
/*
* lock for reading
*/
-static inline void __down_read(struct rw_semaphore *sem)
+static inline int __down_read_common(struct rw_semaphore *sem, int state)
{
- if (!rwsem_read_trylock(sem)) {
- rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE);
+ long count;
+
+ if (!rwsem_read_trylock(sem, &count)) {
+ if (IS_ERR(rwsem_down_read_slowpath(sem, count, state)))
+ return -EINTR;
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
- } else {
- rwsem_set_reader_owned(sem);
}
+ return 0;
+}
+
+static inline void __down_read(struct rw_semaphore *sem)
+{
+ __down_read_common(sem, TASK_UNINTERRUPTIBLE);
+}
+
+static inline int __down_read_interruptible(struct rw_semaphore *sem)
+{
+ return __down_read_common(sem, TASK_INTERRUPTIBLE);
}
static inline int __down_read_killable(struct rw_semaphore *sem)
{
- if (!rwsem_read_trylock(sem)) {
- if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE)))
- return -EINTR;
- DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
- } else {
- rwsem_set_reader_owned(sem);
- }
- return 0;
+ return __down_read_common(sem, TASK_KILLABLE);
}
static inline int __down_read_trylock(struct rw_semaphore *sem)
@@ -1380,44 +1255,30 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
/*
* lock for writing
*/
-static inline void __down_write(struct rw_semaphore *sem)
+static inline int __down_write_common(struct rw_semaphore *sem, int state)
{
- long tmp = RWSEM_UNLOCKED_VALUE;
+ if (unlikely(!rwsem_write_trylock(sem))) {
+ if (IS_ERR(rwsem_down_write_slowpath(sem, state)))
+ return -EINTR;
+ }
- if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
- RWSEM_WRITER_LOCKED)))
- rwsem_down_write_slowpath(sem, TASK_UNINTERRUPTIBLE);
- else
- rwsem_set_owner(sem);
+ return 0;
}
-static inline int __down_write_killable(struct rw_semaphore *sem)
+static inline void __down_write(struct rw_semaphore *sem)
{
- long tmp = RWSEM_UNLOCKED_VALUE;
+ __down_write_common(sem, TASK_UNINTERRUPTIBLE);
+}
- if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
- RWSEM_WRITER_LOCKED))) {
- if (IS_ERR(rwsem_down_write_slowpath(sem, TASK_KILLABLE)))
- return -EINTR;
- } else {
- rwsem_set_owner(sem);
- }
- return 0;
+static inline int __down_write_killable(struct rw_semaphore *sem)
+{
+ return __down_write_common(sem, TASK_KILLABLE);
}
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
- long tmp;
-
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
-
- tmp = RWSEM_UNLOCKED_VALUE;
- if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
- RWSEM_WRITER_LOCKED)) {
- rwsem_set_owner(sem);
- return true;
- }
- return false;
+ return rwsem_write_trylock(sem);
}
/*
@@ -1435,7 +1296,7 @@ static inline void __up_read(struct rw_semaphore *sem)
DEBUG_RWSEMS_WARN_ON(tmp < 0, sem);
if (unlikely((tmp & (RWSEM_LOCK_MASK|RWSEM_FLAG_WAITERS)) ==
RWSEM_FLAG_WAITERS)) {
- clear_wr_nonspinnable(sem);
+ clear_nonspinnable(sem);
rwsem_wake(sem, tmp);
}
}
@@ -1495,6 +1356,20 @@ void __sched down_read(struct rw_semaphore *sem)
}
EXPORT_SYMBOL(down_read);
+int __sched down_read_interruptible(struct rw_semaphore *sem)
+{
+ might_sleep();
+ rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
+
+ if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {
+ rwsem_release(&sem->dep_map, _RET_IP_);
+ return -EINTR;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(down_read_interruptible);
+
int __sched down_read_killable(struct rw_semaphore *sem)
{
might_sleep();
@@ -1605,6 +1480,20 @@ void down_read_nested(struct rw_semaphore *sem, int subclass)
}
EXPORT_SYMBOL(down_read_nested);
+int down_read_killable_nested(struct rw_semaphore *sem, int subclass)
+{
+ might_sleep();
+ rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
+
+ if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) {
+ rwsem_release(&sem->dep_map, _RET_IP_);
+ return -EINTR;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(down_read_killable_nested);
+
void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
{
might_sleep();
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index a899b3f0e2e5..4c24ac8a456c 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -58,10 +58,10 @@ static struct ww_mutex o, o2, o3;
* Normal standalone locks, for the circular and irq-context
* dependency tests:
*/
-static DEFINE_RAW_SPINLOCK(lock_A);
-static DEFINE_RAW_SPINLOCK(lock_B);
-static DEFINE_RAW_SPINLOCK(lock_C);
-static DEFINE_RAW_SPINLOCK(lock_D);
+static DEFINE_SPINLOCK(lock_A);
+static DEFINE_SPINLOCK(lock_B);
+static DEFINE_SPINLOCK(lock_C);
+static DEFINE_SPINLOCK(lock_D);
static DEFINE_RWLOCK(rwlock_A);
static DEFINE_RWLOCK(rwlock_B);
@@ -93,12 +93,12 @@ static DEFINE_RT_MUTEX(rtmutex_D);
* but X* and Y* are different classes. We do this so that
* we do not trigger a real lockup:
*/
-static DEFINE_RAW_SPINLOCK(lock_X1);
-static DEFINE_RAW_SPINLOCK(lock_X2);
-static DEFINE_RAW_SPINLOCK(lock_Y1);
-static DEFINE_RAW_SPINLOCK(lock_Y2);
-static DEFINE_RAW_SPINLOCK(lock_Z1);
-static DEFINE_RAW_SPINLOCK(lock_Z2);
+static DEFINE_SPINLOCK(lock_X1);
+static DEFINE_SPINLOCK(lock_X2);
+static DEFINE_SPINLOCK(lock_Y1);
+static DEFINE_SPINLOCK(lock_Y2);
+static DEFINE_SPINLOCK(lock_Z1);
+static DEFINE_SPINLOCK(lock_Z2);
static DEFINE_RWLOCK(rwlock_X1);
static DEFINE_RWLOCK(rwlock_X2);
@@ -138,10 +138,10 @@ static DEFINE_RT_MUTEX(rtmutex_Z2);
*/
#define INIT_CLASS_FUNC(class) \
static noinline void \
-init_class_##class(raw_spinlock_t *lock, rwlock_t *rwlock, \
+init_class_##class(spinlock_t *lock, rwlock_t *rwlock, \
struct mutex *mutex, struct rw_semaphore *rwsem)\
{ \
- raw_spin_lock_init(lock); \
+ spin_lock_init(lock); \
rwlock_init(rwlock); \
mutex_init(mutex); \
init_rwsem(rwsem); \
@@ -210,10 +210,10 @@ static void init_shared_classes(void)
* Shortcuts for lock/unlock API variants, to keep
* the testcases compact:
*/
-#define L(x) raw_spin_lock(&lock_##x)
-#define U(x) raw_spin_unlock(&lock_##x)
+#define L(x) spin_lock(&lock_##x)
+#define U(x) spin_unlock(&lock_##x)
#define LU(x) L(x); U(x)
-#define SI(x) raw_spin_lock_init(&lock_##x)
+#define SI(x) spin_lock_init(&lock_##x)
#define WL(x) write_lock(&rwlock_##x)
#define WU(x) write_unlock(&rwlock_##x)
@@ -1341,7 +1341,7 @@ GENERATE_PERMUTATIONS_3_EVENTS(irq_read_recursion3_soft_wlock)
#define I2(x) \
do { \
- raw_spin_lock_init(&lock_##x); \
+ spin_lock_init(&lock_##x); \
rwlock_init(&rwlock_##x); \
mutex_init(&mutex_##x); \
init_rwsem(&rwsem_##x); \
@@ -2005,10 +2005,23 @@ static void ww_test_edeadlk_acquire_wrong_slow(void)
static void ww_test_spin_nest_unlocked(void)
{
- raw_spin_lock_nest_lock(&lock_A, &o.base);
+ spin_lock_nest_lock(&lock_A, &o.base);
U(A);
}
+/* This is not a deadlock, because we have X1 to serialize Y1 and Y2 */
+static void ww_test_spin_nest_lock(void)
+{
+ spin_lock(&lock_X1);
+ spin_lock_nest_lock(&lock_Y1, &lock_X1);
+ spin_lock(&lock_A);
+ spin_lock_nest_lock(&lock_Y2, &lock_X1);
+ spin_unlock(&lock_A);
+ spin_unlock(&lock_Y2);
+ spin_unlock(&lock_Y1);
+ spin_unlock(&lock_X1);
+}
+
static void ww_test_unneeded_slow(void)
{
WWAI(&t);
@@ -2226,6 +2239,10 @@ static void ww_tests(void)
dotest(ww_test_spin_nest_unlocked, FAILURE, LOCKTYPE_WW);
pr_cont("\n");
+ print_testname("spinlock nest test");
+ dotest(ww_test_spin_nest_lock, SUCCESS, LOCKTYPE_WW);
+ pr_cont("\n");
+
printk(" -----------------------------------------------------\n");
printk(" |block | try |context|\n");
printk(" -----------------------------------------------------\n");
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