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linux-next/include/linux/spinlock.h
Oleg Nesterov e0acd0a68e sched: fix the theoretical signal_wake_up() vs schedule() race 
This is only theoretical, but after try_to_wake_up(p) was changed
to check p->state under p->pi_lock the code like

	__set_current_state(TASK_INTERRUPTIBLE);
	schedule();

can miss a signal. This is the special case of wait-for-condition,
it relies on try_to_wake_up/schedule interaction and thus it does
not need mb() between __set_current_state() and if(signal_pending).

However, this __set_current_state() can move into the critical
section protected by rq->lock, now that try_to_wake_up() takes
another lock we need to ensure that it can't be reordered with
"if (signal_pending(current))" check inside that section.

The patch is actually one-liner, it simply adds smp_wmb() before
spin_lock_irq(rq->lock). This is what try_to_wake_up() already
does by the same reason.

We turn this wmb() into the new helper, smp_mb__before_spinlock(),
for better documentation and to allow the architectures to change
the default implementation.

While at it, kill smp_mb__after_lock(), it has no callers.

Perhaps we can also add smp_mb__before/after_spinunlock() for
prepare_to_wait().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-08-13 08:19:26 -07:00

406 lines
11 KiB
C
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#ifndef __LINUX_SPINLOCK_H
#define __LINUX_SPINLOCK_H
/*
* include/linux/spinlock.h - generic spinlock/rwlock declarations
*
* here's the role of the various spinlock/rwlock related include files:
*
* on SMP builds:
*
* asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the
* initializers
*
* linux/spinlock_types.h:
* defines the generic type and initializers
*
* asm/spinlock.h: contains the arch_spin_*()/etc. lowlevel
* implementations, mostly inline assembly code
*
* (also included on UP-debug builds:)
*
* linux/spinlock_api_smp.h:
* contains the prototypes for the _spin_*() APIs.
*
* linux/spinlock.h: builds the final spin_*() APIs.
*
* on UP builds:
*
* linux/spinlock_type_up.h:
* contains the generic, simplified UP spinlock type.
* (which is an empty structure on non-debug builds)
*
* linux/spinlock_types.h:
* defines the generic type and initializers
*
* linux/spinlock_up.h:
* contains the arch_spin_*()/etc. version of UP
* builds. (which are NOPs on non-debug, non-preempt
* builds)
*
* (included on UP-non-debug builds:)
*
* linux/spinlock_api_up.h:
* builds the _spin_*() APIs.
*
* linux/spinlock.h: builds the final spin_*() APIs.
*/
#include <linux/typecheck.h>
#include <linux/preempt.h>
#include <linux/linkage.h>
#include <linux/compiler.h>
#include <linux/irqflags.h>
#include <linux/thread_info.h>
#include <linux/kernel.h>
#include <linux/stringify.h>
#include <linux/bottom_half.h>
#include <asm/barrier.h>
/*
* Must define these before including other files, inline functions need them
*/
#define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
#define LOCK_SECTION_START(extra) \
".subsection 1\n\t" \
extra \
".ifndef " LOCK_SECTION_NAME "\n\t" \
LOCK_SECTION_NAME ":\n\t" \
".endif\n"
#define LOCK_SECTION_END \
".previous\n\t"
#define __lockfunc __attribute__((section(".spinlock.text")))
/*
* Pull the arch_spinlock_t and arch_rwlock_t definitions:
*/
#include <linux/spinlock_types.h>
/*
* Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
*/
#ifdef CONFIG_SMP
# include <asm/spinlock.h>
#else
# include <linux/spinlock_up.h>
#endif
#ifdef CONFIG_DEBUG_SPINLOCK
extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
struct lock_class_key *key);
# define raw_spin_lock_init(lock) \
do { \
static struct lock_class_key __key; \
\
__raw_spin_lock_init((lock), #lock, &__key); \
} while (0)
#else
# define raw_spin_lock_init(lock) \
do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
#endif
#define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)
#ifdef CONFIG_GENERIC_LOCKBREAK
#define raw_spin_is_contended(lock) ((lock)->break_lock)
#else
#ifdef arch_spin_is_contended
#define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
#else
#define raw_spin_is_contended(lock) (((void)(lock), 0))
#endif /*arch_spin_is_contended*/
#endif
/*
* Despite its name it doesn't necessarily has to be a full barrier.
* It should only guarantee that a STORE before the critical section
* can not be reordered with a LOAD inside this section.
* spin_lock() is the one-way barrier, this LOAD can not escape out
* of the region. So the default implementation simply ensures that
* a STORE can not move into the critical section, smp_wmb() should
* serialize it with another STORE done by spin_lock().
*/
#ifndef smp_mb__before_spinlock
#define smp_mb__before_spinlock() smp_wmb()
#endif
/**
* raw_spin_unlock_wait - wait until the spinlock gets unlocked
* @lock: the spinlock in question.
*/
#define raw_spin_unlock_wait(lock) arch_spin_unlock_wait(&(lock)->raw_lock)
#ifdef CONFIG_DEBUG_SPINLOCK
extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
#define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
extern int do_raw_spin_trylock(raw_spinlock_t *lock);
extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
#else
static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
{
__acquire(lock);
arch_spin_lock(&lock->raw_lock);
}
static inline void
do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
{
__acquire(lock);
arch_spin_lock_flags(&lock->raw_lock, *flags);
}
static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
{
return arch_spin_trylock(&(lock)->raw_lock);
}
static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
{
arch_spin_unlock(&lock->raw_lock);
__release(lock);
}
#endif
/*
* Define the various spin_lock methods. Note we define these
* regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
* various methods are defined as nops in the case they are not
* required.
*/
#define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
#define raw_spin_lock(lock) _raw_spin_lock(lock)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define raw_spin_lock_nested(lock, subclass) \
_raw_spin_lock_nested(lock, subclass)
# define raw_spin_lock_nest_lock(lock, nest_lock) \
do { \
typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
_raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
} while (0)
#else
# define raw_spin_lock_nested(lock, subclass) _raw_spin_lock(lock)
# define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
#endif
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
#define raw_spin_lock_irqsave(lock, flags) \
do { \
typecheck(unsigned long, flags); \
flags = _raw_spin_lock_irqsave(lock); \
} while (0)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
do { \
typecheck(unsigned long, flags); \
flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
} while (0)
#else
#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
do { \
typecheck(unsigned long, flags); \
flags = _raw_spin_lock_irqsave(lock); \
} while (0)
#endif
#else
#define raw_spin_lock_irqsave(lock, flags) \
do { \
typecheck(unsigned long, flags); \
_raw_spin_lock_irqsave(lock, flags); \
} while (0)
#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
raw_spin_lock_irqsave(lock, flags)
#endif
#define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock)
#define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock)
#define raw_spin_unlock(lock) _raw_spin_unlock(lock)
#define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)
#define raw_spin_unlock_irqrestore(lock, flags) \
do { \
typecheck(unsigned long, flags); \
_raw_spin_unlock_irqrestore(lock, flags); \
} while (0)
#define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
#define raw_spin_trylock_bh(lock) \
__cond_lock(lock, _raw_spin_trylock_bh(lock))
#define raw_spin_trylock_irq(lock) \
({ \
local_irq_disable(); \
raw_spin_trylock(lock) ? \
1 : ({ local_irq_enable(); 0; }); \
})
#define raw_spin_trylock_irqsave(lock, flags) \
({ \
local_irq_save(flags); \
raw_spin_trylock(lock) ? \
1 : ({ local_irq_restore(flags); 0; }); \
})
/**
* raw_spin_can_lock - would raw_spin_trylock() succeed?
* @lock: the spinlock in question.
*/
#define raw_spin_can_lock(lock) (!raw_spin_is_locked(lock))
/* Include rwlock functions */
#include <linux/rwlock.h>
/*
* Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
*/
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
# include <linux/spinlock_api_smp.h>
#else
# include <linux/spinlock_api_up.h>
#endif
/*
* Map the spin_lock functions to the raw variants for PREEMPT_RT=n
*/
static inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
{
return &lock->rlock;
}
#define spin_lock_init(_lock) \
do { \
spinlock_check(_lock); \
raw_spin_lock_init(&(_lock)->rlock); \
} while (0)
static inline void spin_lock(spinlock_t *lock)
{
raw_spin_lock(&lock->rlock);
}
static inline void spin_lock_bh(spinlock_t *lock)
{
raw_spin_lock_bh(&lock->rlock);
}
static inline int spin_trylock(spinlock_t *lock)
{
return raw_spin_trylock(&lock->rlock);
}
#define spin_lock_nested(lock, subclass) \
do { \
raw_spin_lock_nested(spinlock_check(lock), subclass); \
} while (0)
#define spin_lock_nest_lock(lock, nest_lock) \
do { \
raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
} while (0)
static inline void spin_lock_irq(spinlock_t *lock)
{
raw_spin_lock_irq(&lock->rlock);
}
#define spin_lock_irqsave(lock, flags) \
do { \
raw_spin_lock_irqsave(spinlock_check(lock), flags); \
} while (0)
#define spin_lock_irqsave_nested(lock, flags, subclass) \
do { \
raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
} while (0)
static inline void spin_unlock(spinlock_t *lock)
{
raw_spin_unlock(&lock->rlock);
}
static inline void spin_unlock_bh(spinlock_t *lock)
{
raw_spin_unlock_bh(&lock->rlock);
}
static inline void spin_unlock_irq(spinlock_t *lock)
{
raw_spin_unlock_irq(&lock->rlock);
}
static inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
{
raw_spin_unlock_irqrestore(&lock->rlock, flags);
}
static inline int spin_trylock_bh(spinlock_t *lock)
{
return raw_spin_trylock_bh(&lock->rlock);
}
static inline int spin_trylock_irq(spinlock_t *lock)
{
return raw_spin_trylock_irq(&lock->rlock);
}
#define spin_trylock_irqsave(lock, flags) \
({ \
raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
})
static inline void spin_unlock_wait(spinlock_t *lock)
{
raw_spin_unlock_wait(&lock->rlock);
}
static inline int spin_is_locked(spinlock_t *lock)
{
return raw_spin_is_locked(&lock->rlock);
}
static inline int spin_is_contended(spinlock_t *lock)
{
return raw_spin_is_contended(&lock->rlock);
}
static inline int spin_can_lock(spinlock_t *lock)
{
return raw_spin_can_lock(&lock->rlock);
}
#define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
/*
* Pull the atomic_t declaration:
* (asm-mips/atomic.h needs above definitions)
*/
#include <linux/atomic.h>
/**
* atomic_dec_and_lock - lock on reaching reference count zero
* @atomic: the atomic counter
* @lock: the spinlock in question
*
* Decrements @atomic by 1. If the result is 0, returns true and locks
* @lock. Returns false for all other cases.
*/
extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
#define atomic_dec_and_lock(atomic, lock) \
__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
#endif /* __LINUX_SPINLOCK_H */
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