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Message-Id: <20231102110706.460851167@infradead.org>
Date: Thu, 02 Nov 2023 11:44:30 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...uxfoundation.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, peterz@...radead.org,
Jonathan Cameron <jic23@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Oleg Nesterov <oleg@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>
Subject: [PATCH 1/2] cleanup: Add conditional guard support
Adds:
- DEFINE_GUARD_COND() / DEFINE_LOCK_GUARD_1_COND() to extend existing
guards with conditional lock primitives, eg. mutex_trylock(),
mutex_lock_interruptible().
nb. both primitives allow NULL 'locks', which cause the lock to
fail (obviously).
- extends scoped_guard() to not take the body when the the
conditional guard 'fails'. eg.
scoped_guard (mutex_intr, &task->signal_cred_guard_mutex) {
...
}
will only execute the body when the mutex is held.
- provides scoped_cond_guard(name, fail, args...); which extends
scoped_guard() to do fail when the lock-acquire fails.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
---
include/linux/cleanup.h | 52 ++++++++++++++++++++++++++++++++++++++++++++---
include/linux/mutex.h | 3 +-
include/linux/rwsem.h | 8 +++----
include/linux/spinlock.h | 15 +++++++++++++
4 files changed, 70 insertions(+), 8 deletions(-)
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -125,25 +125,55 @@ static inline class_##_name##_t class_##
* trivial wrapper around DEFINE_CLASS() above specifically
* for locks.
*
+ * DEFINE_GUARD_COND(name, ext, condlock)
+ * wrapper around EXTEND_CLASS above to add conditional lock
+ * variants to a base class, eg. mutex_trylock() or
+ * mutex_lock_interruptible().
+ *
* guard(name):
- * an anonymous instance of the (guard) class
+ * an anonymous instance of the (guard) class, not recommended for
+ * conditional locks.
*
* scoped_guard (name, args...) { }:
* similar to CLASS(name, scope)(args), except the variable (with the
* explicit name 'scope') is declard in a for-loop such that its scope is
* bound to the next (compound) statement.
*
+ * for conditional locks the loop body is skipped when the lock is not
+ * acquired.
+ *
+ * scoped_cond_guard (name, fail, args...) { }:
+ * similar to scoped_guard(), except it does fail when the lock
+ * acquire fails.
+ *
*/
#define DEFINE_GUARD(_name, _type, _lock, _unlock) \
- DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T)
+ DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \
+ static inline void * class_##_name##_lock_ptr(class_##_name##_t *_T) \
+ { return *_T; }
+
+#define DEFINE_GUARD_COND(_name, _ext, _condlock) \
+ EXTEND_CLASS(_name, _ext, \
+ ({ void *_t = _T; if (_T && !(_condlock)) _t = NULL; _t; }), \
+ class_##_name##_t _T) \
+ static inline void * class_##_name##_ext##_lock_ptr(class_##_name##_t *_T) \
+ { return class_##_name##_lock_ptr(_T); }
#define guard(_name) \
CLASS(_name, __UNIQUE_ID(guard))
+#define __guard_ptr(_name) class_##_name##_lock_ptr
+
#define scoped_guard(_name, args...) \
for (CLASS(_name, scope)(args), \
- *done = NULL; !done; done = (void *)1)
+ *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
+
+#define scoped_cond_guard(_name, _fail, args...) \
+ for (CLASS(_name, scope)(args), \
+ *done = NULL; !done; done = (void *)1) \
+ if (!__guard_ptr(_name)(&scope)) _fail; \
+ else
/*
* Additional helper macros for generating lock guards with types, either for
@@ -152,6 +182,7 @@ static inline class_##_name##_t class_##
*
* DEFINE_LOCK_GUARD_0(name, lock, unlock, ...)
* DEFINE_LOCK_GUARD_1(name, type, lock, unlock, ...)
+ * DEFINE_LOCK_GUARD_1_COND(name, ext, condlock)
*
* will result in the following type:
*
@@ -173,6 +204,11 @@ typedef struct { \
static inline void class_##_name##_destructor(class_##_name##_t *_T) \
{ \
if (_T->lock) { _unlock; } \
+} \
+ \
+static inline void *class_##_name##_lock_ptr(class_##_name##_t *_T) \
+{ \
+ return _T->lock; \
}
@@ -201,4 +237,14 @@ __DEFINE_LOCK_GUARD_1(_name, _type, _loc
__DEFINE_UNLOCK_GUARD(_name, void, _unlock, __VA_ARGS__) \
__DEFINE_LOCK_GUARD_0(_name, _lock)
+#define DEFINE_LOCK_GUARD_1_COND(_name, _ext, _condlock) \
+ EXTEND_CLASS(_name, _ext, \
+ ({ class_##_name##_t _t = { .lock = l }, *_T = &_t;\
+ if (_T->lock && !(_condlock)) _T->lock = NULL; \
+ _t; }), \
+ typeof_member(class_##_name##_t, lock) l) \
+ static inline void * class_##_name##_ext##_lock_ptr(class_##_name##_t *_T) \
+ { return class_##_name##_lock_ptr(_T); }
+
+
#endif /* __LINUX_GUARDS_H */
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -221,6 +221,7 @@ extern void mutex_unlock(struct mutex *l
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T))
-DEFINE_FREE(mutex, struct mutex *, if (_T) mutex_unlock(_T))
+DEFINE_GUARD_COND(mutex, _try, mutex_trylock(_T))
+DEFINE_GUARD_COND(mutex, _intr, mutex_lock_interruptible(_T) == 0)
#endif /* __LINUX_MUTEX_H */
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -203,11 +203,11 @@ extern void up_read(struct rw_semaphore
extern void up_write(struct rw_semaphore *sem);
DEFINE_GUARD(rwsem_read, struct rw_semaphore *, down_read(_T), up_read(_T))
-DEFINE_GUARD(rwsem_write, struct rw_semaphore *, down_write(_T), up_write(_T))
-
-DEFINE_FREE(up_read, struct rw_semaphore *, if (_T) up_read(_T))
-DEFINE_FREE(up_write, struct rw_semaphore *, if (_T) up_write(_T))
+DEFINE_GUARD_COND(rwsem_read, _try, down_read_trylock(_T))
+DEFINE_GUARD_COND(rwsem_read, _intr, down_read_interruptible(_T) == 0)
+DEFINE_GUARD(rwsem_write, struct rw_semaphore *, down_write(_T), up_write(_T))
+DEFINE_GUARD_COND(rwsem_write, _try, down_write_trylock(_T))
/*
* downgrade write lock to read lock
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -507,6 +507,8 @@ DEFINE_LOCK_GUARD_1(raw_spinlock, raw_sp
raw_spin_lock(_T->lock),
raw_spin_unlock(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(raw_spinlock, _try, raw_spin_trylock(_T->lock))
+
DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,
raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),
raw_spin_unlock(_T->lock))
@@ -515,23 +517,36 @@ DEFINE_LOCK_GUARD_1(raw_spinlock_irq, ra
raw_spin_lock_irq(_T->lock),
raw_spin_unlock_irq(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock))
+
DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
raw_spin_lock_irqsave(_T->lock, _T->flags),
raw_spin_unlock_irqrestore(_T->lock, _T->flags),
unsigned long flags)
+DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try,
+ raw_spin_trylock_irqsave(_T->lock, _T->flags))
+
DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,
spin_lock(_T->lock),
spin_unlock(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(spinlock, _try, spin_trylock(_T->lock))
+
DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
spin_lock_irq(_T->lock),
spin_unlock_irq(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try,
+ spin_trylock_irq(_T->lock))
+
DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
spin_lock_irqsave(_T->lock, _T->flags),
spin_unlock_irqrestore(_T->lock, _T->flags),
unsigned long flags)
+DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try,
+ spin_trylock_irqsave(_T->lock, _T->flags))
+
#undef __LINUX_INSIDE_SPINLOCK_H
#endif /* __LINUX_SPINLOCK_H */
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