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Date: Sat, 19 Jul 2014 11:11:59 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
cc: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>
Subject: [GIT pull] locking updates for 3.16
Linus,
please pull the latest locking-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus
The locking department delivers:
* A rather large and intrusive bundle of fixes to address serious
performance regressions introduced by the new rwsem / mcs
technology. Simpler solutions have been discussed, but they
would have been ugly bandaids with more risk than doing the
right thing.
* Make the rwsem spin on owner technology opt-in for
architectures and enable it only on the known to work ones.
* A few fixes to the lockdep userspace library
Thanks,
tglx
------------------>
Davidlohr Bueso (1):
locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER
Jason Low (6):
locking/rwsem: Allow conservative optimistic spinning when readers have lock
locking/spinlocks/mcs: Rename optimistic_spin_queue() to optimistic_spin_node()
locking/spinlocks/mcs: Convert osq lock to atomic_t to reduce overhead
locking/spinlocks/mcs: Introduce and use init macro and function for osq locks
locking/spinlocks/mcs: Micro-optimize osq_unlock()
locking/rwsem: Reduce the size of struct rw_semaphore
Peter Zijlstra (2):
locking/rwsem: Rename 'activity' to 'count'
locking/mutex: Disable optimistic spinning on some architectures
S. Lockwood-Childs (1):
tools/liblockdep: Account for bitfield changes in lockdeps lock_acquire
Sasha Levin (1):
tools/liblockdep: Remove debug print left over from development
zhangdianfang (1):
tools/liblockdep: Fix comparison of a boolean value with a value of 2
arch/arm/Kconfig | 1 +
arch/arm64/Kconfig | 1 +
arch/powerpc/Kconfig | 1 +
arch/sparc/Kconfig | 1 +
arch/x86/Kconfig | 1 +
include/linux/mutex.h | 4 +-
include/linux/osq_lock.h | 27 +++++++++++
include/linux/rwsem-spinlock.h | 8 ++--
include/linux/rwsem.h | 34 +++++++-------
kernel/Kconfig.locks | 9 +++-
kernel/locking/mcs_spinlock.c | 64 ++++++++++++++++++++-------
kernel/locking/mcs_spinlock.h | 9 ++--
kernel/locking/mutex.c | 2 +-
kernel/locking/rwsem-spinlock.c | 28 ++++++------
kernel/locking/rwsem-xadd.c | 16 +++----
kernel/locking/rwsem.c | 2 +-
tools/lib/lockdep/include/liblockdep/mutex.h | 4 +-
tools/lib/lockdep/include/liblockdep/rwlock.h | 8 ++--
tools/lib/lockdep/preload.c | 20 ++++-----
19 files changed, 154 insertions(+), 86 deletions(-)
create mode 100644 include/linux/osq_lock.h
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 245058b..88acf8b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -6,6 +6,7 @@ config ARM
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAVE_CUSTOM_GPIO_H
select ARCH_MIGHT_HAVE_PC_PARPORT
+ select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF
select ARCH_WANT_IPC_PARSE_VERSION
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a474de34..839f48c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -4,6 +4,7 @@ config ARM64
select ARCH_HAS_OPP
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_USE_CMPXCHG_LOCKREF
+ select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_WANT_OPTIONAL_GPIOLIB
select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index fefe7c8..80b94b0 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -145,6 +145,7 @@ config PPC
select HAVE_IRQ_EXIT_ON_IRQ_STACK
select ARCH_USE_CMPXCHG_LOCKREF if PPC64
select HAVE_ARCH_AUDITSYSCALL
+ select ARCH_SUPPORTS_ATOMIC_RMW
config GENERIC_CSUM
def_bool CPU_LITTLE_ENDIAN
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 29f2e98..407c87d 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -78,6 +78,7 @@ config SPARC64
select HAVE_C_RECORDMCOUNT
select NO_BOOTMEM
select HAVE_ARCH_AUDITSYSCALL
+ select ARCH_SUPPORTS_ATOMIC_RMW
config ARCH_DEFCONFIG
string
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a8f749e..d24887b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -131,6 +131,7 @@ config X86
select HAVE_CC_STACKPROTECTOR
select GENERIC_CPU_AUTOPROBE
select HAVE_ARCH_AUDITSYSCALL
+ select ARCH_SUPPORTS_ATOMIC_RMW
config INSTRUCTION_DECODER
def_bool y
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 11692de..42aa9b9 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -17,6 +17,7 @@
#include <linux/lockdep.h>
#include <linux/atomic.h>
#include <asm/processor.h>
+#include <linux/osq_lock.h>
/*
* Simple, straightforward mutexes with strict semantics:
@@ -46,7 +47,6 @@
* - detects multi-task circular deadlocks and prints out all affected
* locks and tasks (and only those tasks)
*/
-struct optimistic_spin_queue;
struct mutex {
/* 1: unlocked, 0: locked, negative: locked, possible waiters */
atomic_t count;
@@ -56,7 +56,7 @@ struct mutex {
struct task_struct *owner;
#endif
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
- struct optimistic_spin_queue *osq; /* Spinner MCS lock */
+ struct optimistic_spin_queue osq; /* Spinner MCS lock */
#endif
#ifdef CONFIG_DEBUG_MUTEXES
const char *name;
diff --git a/include/linux/osq_lock.h b/include/linux/osq_lock.h
new file mode 100644
index 0000000..90230d5
--- /dev/null
+++ b/include/linux/osq_lock.h
@@ -0,0 +1,27 @@
+#ifndef __LINUX_OSQ_LOCK_H
+#define __LINUX_OSQ_LOCK_H
+
+/*
+ * An MCS like lock especially tailored for optimistic spinning for sleeping
+ * lock implementations (mutex, rwsem, etc).
+ */
+
+#define OSQ_UNLOCKED_VAL (0)
+
+struct optimistic_spin_queue {
+ /*
+ * Stores an encoded value of the CPU # of the tail node in the queue.
+ * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
+ */
+ atomic_t tail;
+};
+
+/* Init macro and function. */
+#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
+
+static inline void osq_lock_init(struct optimistic_spin_queue *lock)
+{
+ atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
+}
+
+#endif
diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
index d5b13bc..561e861 100644
--- a/include/linux/rwsem-spinlock.h
+++ b/include/linux/rwsem-spinlock.h
@@ -15,13 +15,13 @@
#ifdef __KERNEL__
/*
* the rw-semaphore definition
- * - if activity is 0 then there are no active readers or writers
- * - if activity is +ve then that is the number of active readers
- * - if activity is -1 then there is one active writer
+ * - if count is 0 then there are no active readers or writers
+ * - if count is +ve then that is the number of active readers
+ * - if count is -1 then there is one active writer
* - if wait_list is not empty, then there are processes waiting for the semaphore
*/
struct rw_semaphore {
- __s32 activity;
+ __s32 count;
raw_spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 8d79708..035d3c5 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -13,10 +13,11 @@
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/spinlock.h>
-
#include <linux/atomic.h>
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+#include <linux/osq_lock.h>
+#endif
-struct optimistic_spin_queue;
struct rw_semaphore;
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
@@ -25,15 +26,15 @@ struct rw_semaphore;
/* All arch specific implementations share the same struct */
struct rw_semaphore {
long count;
- raw_spinlock_t wait_lock;
struct list_head wait_list;
-#ifdef CONFIG_SMP
+ raw_spinlock_t wait_lock;
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+ struct optimistic_spin_queue osq; /* spinner MCS lock */
/*
* Write owner. Used as a speculative check to see
* if the owner is running on the cpu.
*/
struct task_struct *owner;
- struct optimistic_spin_queue *osq; /* spinner MCS lock */
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
@@ -64,22 +65,19 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif
-#if defined(CONFIG_SMP) && !defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
-#define __RWSEM_INITIALIZER(name) \
- { RWSEM_UNLOCKED_VALUE, \
- __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock), \
- LIST_HEAD_INIT((name).wait_list), \
- NULL, /* owner */ \
- NULL /* mcs lock */ \
- __RWSEM_DEP_MAP_INIT(name) }
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
#else
-#define __RWSEM_INITIALIZER(name) \
- { RWSEM_UNLOCKED_VALUE, \
- __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock), \
- LIST_HEAD_INIT((name).wait_list) \
- __RWSEM_DEP_MAP_INIT(name) }
+#define __RWSEM_OPT_INIT(lockname)
#endif
+#define __RWSEM_INITIALIZER(name) \
+ { .count = RWSEM_UNLOCKED_VALUE, \
+ .wait_list = LIST_HEAD_INIT((name).wait_list), \
+ .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
+ __RWSEM_OPT_INIT(name) \
+ __RWSEM_DEP_MAP_INIT(name) }
+
#define DECLARE_RWSEM(name) \
struct rw_semaphore name = __RWSEM_INITIALIZER(name)
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index 35536d9..76768ee 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -220,9 +220,16 @@ config INLINE_WRITE_UNLOCK_IRQRESTORE
endif
+config ARCH_SUPPORTS_ATOMIC_RMW
+ bool
+
config MUTEX_SPIN_ON_OWNER
def_bool y
- depends on SMP && !DEBUG_MUTEXES
+ depends on SMP && !DEBUG_MUTEXES && ARCH_SUPPORTS_ATOMIC_RMW
+
+config RWSEM_SPIN_ON_OWNER
+ def_bool y
+ depends on SMP && RWSEM_XCHGADD_ALGORITHM && ARCH_SUPPORTS_ATOMIC_RMW
config ARCH_USE_QUEUE_RWLOCK
bool
diff --git a/kernel/locking/mcs_spinlock.c b/kernel/locking/mcs_spinlock.c
index 838dc9e..be9ee15 100644
--- a/kernel/locking/mcs_spinlock.c
+++ b/kernel/locking/mcs_spinlock.c
@@ -14,21 +14,47 @@
* called from interrupt context and we have preemption disabled while
* spinning.
*/
-static DEFINE_PER_CPU_SHARED_ALIGNED(struct optimistic_spin_queue, osq_node);
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct optimistic_spin_node, osq_node);
+
+/*
+ * We use the value 0 to represent "no CPU", thus the encoded value
+ * will be the CPU number incremented by 1.
+ */
+static inline int encode_cpu(int cpu_nr)
+{
+ return cpu_nr + 1;
+}
+
+static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val)
+{
+ int cpu_nr = encoded_cpu_val - 1;
+
+ return per_cpu_ptr(&osq_node, cpu_nr);
+}
/*
* Get a stable @node->next pointer, either for unlock() or unqueue() purposes.
* Can return NULL in case we were the last queued and we updated @lock instead.
*/
-static inline struct optimistic_spin_queue *
-osq_wait_next(struct optimistic_spin_queue **lock,
- struct optimistic_spin_queue *node,
- struct optimistic_spin_queue *prev)
+static inline struct optimistic_spin_node *
+osq_wait_next(struct optimistic_spin_queue *lock,
+ struct optimistic_spin_node *node,
+ struct optimistic_spin_node *prev)
{
- struct optimistic_spin_queue *next = NULL;
+ struct optimistic_spin_node *next = NULL;
+ int curr = encode_cpu(smp_processor_id());
+ int old;
+
+ /*
+ * If there is a prev node in queue, then the 'old' value will be
+ * the prev node's CPU #, else it's set to OSQ_UNLOCKED_VAL since if
+ * we're currently last in queue, then the queue will then become empty.
+ */
+ old = prev ? prev->cpu : OSQ_UNLOCKED_VAL;
for (;;) {
- if (*lock == node && cmpxchg(lock, node, prev) == node) {
+ if (atomic_read(&lock->tail) == curr &&
+ atomic_cmpxchg(&lock->tail, curr, old) == curr) {
/*
* We were the last queued, we moved @lock back. @prev
* will now observe @lock and will complete its
@@ -59,18 +85,23 @@ osq_wait_next(struct optimistic_spin_queue **lock,
return next;
}
-bool osq_lock(struct optimistic_spin_queue **lock)
+bool osq_lock(struct optimistic_spin_queue *lock)
{
- struct optimistic_spin_queue *node = this_cpu_ptr(&osq_node);
- struct optimistic_spin_queue *prev, *next;
+ struct optimistic_spin_node *node = this_cpu_ptr(&osq_node);
+ struct optimistic_spin_node *prev, *next;
+ int curr = encode_cpu(smp_processor_id());
+ int old;
node->locked = 0;
node->next = NULL;
+ node->cpu = curr;
- node->prev = prev = xchg(lock, node);
- if (likely(prev == NULL))
+ old = atomic_xchg(&lock->tail, curr);
+ if (old == OSQ_UNLOCKED_VAL)
return true;
+ prev = decode_cpu(old);
+ node->prev = prev;
ACCESS_ONCE(prev->next) = node;
/*
@@ -149,20 +180,21 @@ unqueue:
return false;
}
-void osq_unlock(struct optimistic_spin_queue **lock)
+void osq_unlock(struct optimistic_spin_queue *lock)
{
- struct optimistic_spin_queue *node = this_cpu_ptr(&osq_node);
- struct optimistic_spin_queue *next;
+ struct optimistic_spin_node *node, *next;
+ int curr = encode_cpu(smp_processor_id());
/*
* Fast path for the uncontended case.
*/
- if (likely(cmpxchg(lock, node, NULL) == node))
+ if (likely(atomic_cmpxchg(&lock->tail, curr, OSQ_UNLOCKED_VAL) == curr))
return;
/*
* Second most likely case.
*/
+ node = this_cpu_ptr(&osq_node);
next = xchg(&node->next, NULL);
if (next) {
ACCESS_ONCE(next->locked) = 1;
diff --git a/kernel/locking/mcs_spinlock.h b/kernel/locking/mcs_spinlock.h
index a2dbac4..74356dc 100644
--- a/kernel/locking/mcs_spinlock.h
+++ b/kernel/locking/mcs_spinlock.h
@@ -118,12 +118,13 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
* mutex_lock()/rwsem_down_{read,write}() etc.
*/
-struct optimistic_spin_queue {
- struct optimistic_spin_queue *next, *prev;
+struct optimistic_spin_node {
+ struct optimistic_spin_node *next, *prev;
int locked; /* 1 if lock acquired */
+ int cpu; /* encoded CPU # value */
};
-extern bool osq_lock(struct optimistic_spin_queue **lock);
-extern void osq_unlock(struct optimistic_spin_queue **lock);
+extern bool osq_lock(struct optimistic_spin_queue *lock);
+extern void osq_unlock(struct optimistic_spin_queue *lock);
#endif /* __LINUX_MCS_SPINLOCK_H */
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index bc73d33..acca2c1 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -60,7 +60,7 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
INIT_LIST_HEAD(&lock->wait_list);
mutex_clear_owner(lock);
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
- lock->osq = NULL;
+ osq_lock_init(&lock->osq);
#endif
debug_mutex_init(lock, name, key);
diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c
index 9be8a91..2c93571 100644
--- a/kernel/locking/rwsem-spinlock.c
+++ b/kernel/locking/rwsem-spinlock.c
@@ -26,7 +26,7 @@ int rwsem_is_locked(struct rw_semaphore *sem)
unsigned long flags;
if (raw_spin_trylock_irqsave(&sem->wait_lock, flags)) {
- ret = (sem->activity != 0);
+ ret = (sem->count != 0);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
}
return ret;
@@ -46,7 +46,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
debug_check_no_locks_freed((void *)sem, sizeof(*sem));
lockdep_init_map(&sem->dep_map, name, key, 0);
#endif
- sem->activity = 0;
+ sem->count = 0;
raw_spin_lock_init(&sem->wait_lock);
INIT_LIST_HEAD(&sem->wait_list);
}
@@ -95,7 +95,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
waiter = list_entry(next, struct rwsem_waiter, list);
} while (waiter->type != RWSEM_WAITING_FOR_WRITE);
- sem->activity += woken;
+ sem->count += woken;
out:
return sem;
@@ -126,9 +126,9 @@ void __sched __down_read(struct rw_semaphore *sem)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
- if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ if (sem->count >= 0 && list_empty(&sem->wait_list)) {
/* granted */
- sem->activity++;
+ sem->count++;
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
goto out;
}
@@ -170,9 +170,9 @@ int __down_read_trylock(struct rw_semaphore *sem)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
- if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ if (sem->count >= 0 && list_empty(&sem->wait_list)) {
/* granted */
- sem->activity++;
+ sem->count++;
ret = 1;
}
@@ -206,7 +206,7 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
* itself into sleep and waiting for system woke it or someone
* else in the head of the wait list up.
*/
- if (sem->activity == 0)
+ if (sem->count == 0)
break;
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
@@ -214,7 +214,7 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
}
/* got the lock */
- sem->activity = -1;
+ sem->count = -1;
list_del(&waiter.list);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
@@ -235,9 +235,9 @@ int __down_write_trylock(struct rw_semaphore *sem)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
- if (sem->activity == 0) {
+ if (sem->count == 0) {
/* got the lock */
- sem->activity = -1;
+ sem->count = -1;
ret = 1;
}
@@ -255,7 +255,7 @@ void __up_read(struct rw_semaphore *sem)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
- if (--sem->activity == 0 && !list_empty(&sem->wait_list))
+ if (--sem->count == 0 && !list_empty(&sem->wait_list))
sem = __rwsem_wake_one_writer(sem);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
@@ -270,7 +270,7 @@ void __up_write(struct rw_semaphore *sem)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
- sem->activity = 0;
+ sem->count = 0;
if (!list_empty(&sem->wait_list))
sem = __rwsem_do_wake(sem, 1);
@@ -287,7 +287,7 @@ void __downgrade_write(struct rw_semaphore *sem)
raw_spin_lock_irqsave(&sem->wait_lock, flags);
- sem->activity = 1;
+ sem->count = 1;
if (!list_empty(&sem->wait_list))
sem = __rwsem_do_wake(sem, 0);
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index dacc321..a2391ac 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -82,9 +82,9 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
sem->count = RWSEM_UNLOCKED_VALUE;
raw_spin_lock_init(&sem->wait_lock);
INIT_LIST_HEAD(&sem->wait_list);
-#ifdef CONFIG_SMP
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
sem->owner = NULL;
- sem->osq = NULL;
+ osq_lock_init(&sem->osq);
#endif
}
@@ -262,7 +262,7 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
return false;
}
-#ifdef CONFIG_SMP
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
/*
* Try to acquire write lock before the writer has been put on wait queue.
*/
@@ -285,10 +285,10 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
{
struct task_struct *owner;
- bool on_cpu = true;
+ bool on_cpu = false;
if (need_resched())
- return 0;
+ return false;
rcu_read_lock();
owner = ACCESS_ONCE(sem->owner);
@@ -297,9 +297,9 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
rcu_read_unlock();
/*
- * If sem->owner is not set, the rwsem owner may have
- * just acquired it and not set the owner yet or the rwsem
- * has been released.
+ * If sem->owner is not set, yet we have just recently entered the
+ * slowpath, then there is a possibility reader(s) may have the lock.
+ * To be safe, avoid spinning in these situations.
*/
return on_cpu;
}
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 42f806d..e2d3bc7 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -12,7 +12,7 @@
#include <linux/atomic.h>
-#if defined(CONFIG_SMP) && defined(CONFIG_RWSEM_XCHGADD_ALGORITHM)
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
static inline void rwsem_set_owner(struct rw_semaphore *sem)
{
sem->owner = current;
diff --git a/tools/lib/lockdep/include/liblockdep/mutex.h b/tools/lib/lockdep/include/liblockdep/mutex.h
index c342f70..ee53a42 100644
--- a/tools/lib/lockdep/include/liblockdep/mutex.h
+++ b/tools/lib/lockdep/include/liblockdep/mutex.h
@@ -35,7 +35,7 @@ static inline int __mutex_init(liblockdep_pthread_mutex_t *lock,
static inline int liblockdep_pthread_mutex_lock(liblockdep_pthread_mutex_t *lock)
{
- lock_acquire(&lock->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&lock->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);
return pthread_mutex_lock(&lock->mutex);
}
@@ -47,7 +47,7 @@ static inline int liblockdep_pthread_mutex_unlock(liblockdep_pthread_mutex_t *lo
static inline int liblockdep_pthread_mutex_trylock(liblockdep_pthread_mutex_t *lock)
{
- lock_acquire(&lock->dep_map, 0, 1, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&lock->dep_map, 0, 1, 0, 1, NULL, (unsigned long)_RET_IP_);
return pthread_mutex_trylock(&lock->mutex) == 0 ? 1 : 0;
}
diff --git a/tools/lib/lockdep/include/liblockdep/rwlock.h b/tools/lib/lockdep/include/liblockdep/rwlock.h
index a680ab8..4ec03f8 100644
--- a/tools/lib/lockdep/include/liblockdep/rwlock.h
+++ b/tools/lib/lockdep/include/liblockdep/rwlock.h
@@ -36,7 +36,7 @@ static inline int __rwlock_init(liblockdep_pthread_rwlock_t *lock,
static inline int liblockdep_pthread_rwlock_rdlock(liblockdep_pthread_rwlock_t *lock)
{
- lock_acquire(&lock->dep_map, 0, 0, 2, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&lock->dep_map, 0, 0, 2, 1, NULL, (unsigned long)_RET_IP_);
return pthread_rwlock_rdlock(&lock->rwlock);
}
@@ -49,19 +49,19 @@ static inline int liblockdep_pthread_rwlock_unlock(liblockdep_pthread_rwlock_t *
static inline int liblockdep_pthread_rwlock_wrlock(liblockdep_pthread_rwlock_t *lock)
{
- lock_acquire(&lock->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&lock->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);
return pthread_rwlock_wrlock(&lock->rwlock);
}
static inline int liblockdep_pthread_rwlock_tryrdlock(liblockdep_pthread_rwlock_t *lock)
{
- lock_acquire(&lock->dep_map, 0, 1, 2, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&lock->dep_map, 0, 1, 2, 1, NULL, (unsigned long)_RET_IP_);
return pthread_rwlock_tryrdlock(&lock->rwlock) == 0 ? 1 : 0;
}
static inline int liblockdep_pthread_rwlock_trywlock(liblockdep_pthread_rwlock_t *lock)
{
- lock_acquire(&lock->dep_map, 0, 1, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&lock->dep_map, 0, 1, 0, 1, NULL, (unsigned long)_RET_IP_);
return pthread_rwlock_trywlock(&lock->rwlock) == 0 ? 1 : 0;
}
diff --git a/tools/lib/lockdep/preload.c b/tools/lib/lockdep/preload.c
index 23bd69c..6f80360 100644
--- a/tools/lib/lockdep/preload.c
+++ b/tools/lib/lockdep/preload.c
@@ -92,7 +92,7 @@ enum { none, prepare, done, } __init_state;
static void init_preload(void);
static void try_init_preload(void)
{
- if (!__init_state != done)
+ if (__init_state != done)
init_preload();
}
@@ -252,7 +252,7 @@ int pthread_mutex_lock(pthread_mutex_t *mutex)
try_init_preload();
- lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 2, NULL,
+ lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 1, NULL,
(unsigned long)_RET_IP_);
/*
* Here's the thing with pthread mutexes: unlike the kernel variant,
@@ -281,7 +281,7 @@ int pthread_mutex_trylock(pthread_mutex_t *mutex)
try_init_preload();
- lock_acquire(&__get_lock(mutex)->dep_map, 0, 1, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(mutex)->dep_map, 0, 1, 0, 1, NULL, (unsigned long)_RET_IP_);
r = ll_pthread_mutex_trylock(mutex);
if (r)
lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);
@@ -303,7 +303,7 @@ int pthread_mutex_unlock(pthread_mutex_t *mutex)
*/
r = ll_pthread_mutex_unlock(mutex);
if (r)
- lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);
return r;
}
@@ -352,7 +352,7 @@ int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
init_preload();
- lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 2, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 2, 1, NULL, (unsigned long)_RET_IP_);
r = ll_pthread_rwlock_rdlock(rwlock);
if (r)
lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
@@ -366,7 +366,7 @@ int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
init_preload();
- lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 2, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 2, 1, NULL, (unsigned long)_RET_IP_);
r = ll_pthread_rwlock_tryrdlock(rwlock);
if (r)
lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
@@ -380,7 +380,7 @@ int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
init_preload();
- lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 0, 1, NULL, (unsigned long)_RET_IP_);
r = ll_pthread_rwlock_trywrlock(rwlock);
if (r)
lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
@@ -394,7 +394,7 @@ int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
init_preload();
- lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);
r = ll_pthread_rwlock_wrlock(rwlock);
if (r)
lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
@@ -411,7 +411,7 @@ int pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
r = ll_pthread_rwlock_unlock(rwlock);
if (r)
- lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);
return r;
}
@@ -439,8 +439,6 @@ __attribute__((constructor)) static void init_preload(void)
ll_pthread_rwlock_unlock = dlsym(RTLD_NEXT, "pthread_rwlock_unlock");
#endif
- printf("%p\n", ll_pthread_mutex_trylock);fflush(stdout);
-
lockdep_init();
__init_state = done;
--
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