[tip: locking/core] cleanup: Add conditional guard support
From: tip-bot2 for Peter Zijlstra
Date: Wed Nov 15 2023 - 04:20:30 EST
The following commit has been merged into the locking/core branch of tip:
Commit-ID: e4ab322fbaaaf84b23d6cb0e3317a7f68baf36dc
Gitweb: https://git.kernel.org/tip/e4ab322fbaaaf84b23d6cb0e3317a7f68baf36dc
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Sun, 17 Sep 2023 13:22:17 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 15 Nov 2023 10:15:33 +01:00
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@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20231102110706.460851167%40infradead.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(-)
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 9f1a9c4..c2d09bc 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -125,25 +125,55 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
* 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_##_name##ext##_constructor(_init_args) \
*
* 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, _lock)
__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 */
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index a33aa9e..95d1130 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -221,6 +221,7 @@ extern void mutex_unlock(struct mutex *lock);
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 */
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 1dd530c..9c29689 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -203,11 +203,11 @@ extern void up_read(struct rw_semaphore *sem);
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
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 31d3d74..ceb56b3 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -507,6 +507,8 @@ DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t,
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, raw_spinlock_t,
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 */