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Commit 3469d261 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'locking-rwsem-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull support for killable rwsems from Ingo Molnar:
 "This, by Michal Hocko, implements down_write_killable().

  The main usecase will be to update mm_sem usage sites to use this new
  API, to allow the mm-reaper introduced in commit aac45363 ("mm,
  oom: introduce oom reaper") to tear down oom victim address spaces
  asynchronously with minimum latencies and without deadlock worries"

[ The vfs will want it too as the inode lock is changed from a mutex to
  a rwsem due to the parallel lookup and readdir updates ]

* 'locking-rwsem-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rwsem: Fix comment on register clobbering
  locking/rwsem: Fix down_write_killable()
  locking/rwsem, x86: Add frame annotation for call_rwsem_down_write_failed_killable()
  locking/rwsem: Provide down_write_killable()
  locking/rwsem, x86: Provide __down_write_killable()
  locking/rwsem, s390: Provide __down_write_killable()
  locking/rwsem, ia64: Provide __down_write_killable()
  locking/rwsem, alpha: Provide __down_write_killable()
  locking/rwsem: Introduce basis for down_write_killable()
  locking/rwsem, sparc: Drop superfluous arch specific implementation
  locking/rwsem, sh: Drop superfluous arch specific implementation
  locking/rwsem, xtensa: Drop superfluous arch specific implementation
  locking/rwsem: Drop explicit memory barriers
  locking/rwsem: Get rid of __down_write_nested()
parents 1c19b68a 4544ba8c

arch/alpha/include/asm/rwsem.h

+16 −2
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) 
	return res >= 0 ? 1 : 0;

}



static inline void __down_write(struct rw_semaphore *sem)

static inline long ___down_write(struct rw_semaphore *sem)

{

	long oldcount;

#ifndef	CONFIG_SMP
@@ -83,10 +83,24 @@ static inline void __down_write(struct rw_semaphore *sem) 
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)

	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");

#endif

	if (unlikely(oldcount))

	return oldcount;

}



static inline void __down_write(struct rw_semaphore *sem)

{

	if (unlikely(___down_write(sem)))

		rwsem_down_write_failed(sem);

}



static inline int __down_write_killable(struct rw_semaphore *sem)

{

	if (unlikely(___down_write(sem)))

		if (IS_ERR(rwsem_down_write_failed_killable(sem)))

			return -EINTR;



	return 0;

}



/*

 * trylock for writing -- returns 1 if successful, 0 if contention

 */

arch/ia64/include/asm/rwsem.h

+19 −3
Original line number Diff line number Diff line
@@ -49,8 +49,8 @@ __down_read (struct rw_semaphore *sem) 
/*

 * lock for writing

 */

static inline void

__down_write (struct rw_semaphore *sem)

static inline long

___down_write (struct rw_semaphore *sem)

{

	long old, new;
@@ -59,10 +59,26 @@ __down_write (struct rw_semaphore *sem) 
		new = old + RWSEM_ACTIVE_WRITE_BIAS;

	} while (cmpxchg_acq(&sem->count, old, new) != old);



	if (old != 0)

	return old;

}



static inline void

__down_write (struct rw_semaphore *sem)

{

	if (___down_write(sem))

		rwsem_down_write_failed(sem);

}



static inline int

__down_write_killable (struct rw_semaphore *sem)

{

	if (___down_write(sem))

		if (IS_ERR(rwsem_down_write_failed_killable(sem)))

			return -EINTR;



	return 0;

}



/*

 * unlock after reading

 */

arch/s390/include/asm/rwsem.h

+14 −4
Original line number Diff line number Diff line
@@ -90,7 +90,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) 
/*

 * lock for writing

 */

static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)

static inline long ___down_write(struct rw_semaphore *sem)

{

	signed long old, new, tmp;
@@ -104,13 +104,23 @@ static inline void __down_write_nested(struct rw_semaphore *sem, int subclass) 
		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "m" (tmp)

		: "cc", "memory");

	if (old != 0)

		rwsem_down_write_failed(sem);



	return old;

}



static inline void __down_write(struct rw_semaphore *sem)

{

	__down_write_nested(sem, 0);

	if (___down_write(sem))

		rwsem_down_write_failed(sem);

}



static inline int __down_write_killable(struct rw_semaphore *sem)

{

	if (___down_write(sem))

		if (IS_ERR(rwsem_down_write_failed_killable(sem)))

			return -EINTR;



	return 0;

}



/*

arch/sh/include/asm/Kbuild

+1 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ generic-y += percpu.h 
generic-y += poll.h

generic-y += preempt.h

generic-y += resource.h

generic-y += rwsem.h

generic-y += sembuf.h

generic-y += serial.h

generic-y += shmbuf.h

arch/sh/include/asm/rwsem.h

deleted100644 → 0
+0 −132
Original line number Diff line number Diff line 
/*

 * include/asm-sh/rwsem.h: R/W semaphores for SH using the stuff

 * in lib/rwsem.c.

 */



#ifndef _ASM_SH_RWSEM_H

#define _ASM_SH_RWSEM_H



#ifndef _LINUX_RWSEM_H

#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"

#endif



#ifdef __KERNEL__



#define RWSEM_UNLOCKED_VALUE		0x00000000

#define RWSEM_ACTIVE_BIAS		0x00000001

#define RWSEM_ACTIVE_MASK		0x0000ffff

#define RWSEM_WAITING_BIAS		(-0x00010000)

#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS

#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)



/*

 * lock for reading

 */

static inline void __down_read(struct rw_semaphore *sem)

{

	if (atomic_inc_return((atomic_t *)(&sem->count)) > 0)

		smp_wmb();

	else

		rwsem_down_read_failed(sem);

}



static inline int __down_read_trylock(struct rw_semaphore *sem)

{

	int tmp;



	while ((tmp = sem->count) >= 0) {

		if (tmp == cmpxchg(&sem->count, tmp,

				   tmp + RWSEM_ACTIVE_READ_BIAS)) {

			smp_wmb();

			return 1;

		}

	}

	return 0;

}



/*

 * lock for writing

 */

static inline void __down_write(struct rw_semaphore *sem)

{

	int tmp;



	tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,

				(atomic_t *)(&sem->count));

	if (tmp == RWSEM_ACTIVE_WRITE_BIAS)

		smp_wmb();

	else

		rwsem_down_write_failed(sem);

}



static inline int __down_write_trylock(struct rw_semaphore *sem)

{

	int tmp;



	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,

		      RWSEM_ACTIVE_WRITE_BIAS);

	smp_wmb();

	return tmp == RWSEM_UNLOCKED_VALUE;

}



/*

 * unlock after reading

 */

static inline void __up_read(struct rw_semaphore *sem)

{

	int tmp;



	smp_wmb();

	tmp = atomic_dec_return((atomic_t *)(&sem->count));

	if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)

		rwsem_wake(sem);

}



/*

 * unlock after writing

 */

static inline void __up_write(struct rw_semaphore *sem)

{

	smp_wmb();

	if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,

			      (atomic_t *)(&sem->count)) < 0)

		rwsem_wake(sem);

}



/*

 * implement atomic add functionality

 */

static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)

{

	atomic_add(delta, (atomic_t *)(&sem->count));

}



/*

 * downgrade write lock to read lock

 */

static inline void __downgrade_write(struct rw_semaphore *sem)

{

	int tmp;



	smp_wmb();

	tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));

	if (tmp < 0)

		rwsem_downgrade_wake(sem);

}



static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)

{

	__down_write(sem);

}



/*

 * implement exchange and add functionality

 */

static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)

{

	smp_mb();

	return atomic_add_return(delta, (atomic_t *)(&sem->count));

}



#endif /* __KERNEL__ */

#endif /* _ASM_SH_RWSEM_H */