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authorLinus Torvalds <torvalds@linux-foundation.org>2016-05-16 13:41:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-16 13:41:02 -0700
commit3469d261eac65912927dca13ee8f77c744ad7aa2 (patch)
tree09b25f80c065d52ee6e158c189ba44bb28bb76fc /arch
parent1c19b68a279c58d6da4379bf8b6d679a300a1daf (diff)
parent4544ba8c6b1743499cabb682897a469911845f15 (diff)
downloadlinux-3469d261eac65912927dca13ee8f77c744ad7aa2.tar.bz2
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 aac453635549 ("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()
Diffstat (limited to 'arch')
-rw-r--r--arch/alpha/include/asm/rwsem.h18
-rw-r--r--arch/ia64/include/asm/rwsem.h22
-rw-r--r--arch/s390/include/asm/rwsem.h18
-rw-r--r--arch/sh/include/asm/Kbuild1
-rw-r--r--arch/sh/include/asm/rwsem.h132
-rw-r--r--arch/sparc/include/asm/Kbuild1
-rw-r--r--arch/sparc/include/asm/rwsem.h124
-rw-r--r--arch/x86/include/asm/rwsem.h42
-rw-r--r--arch/x86/lib/rwsem.S16
-rw-r--r--arch/xtensa/include/asm/Kbuild1
-rw-r--r--arch/xtensa/include/asm/rwsem.h131
11 files changed, 92 insertions, 414 deletions
diff --git a/arch/alpha/include/asm/rwsem.h b/arch/alpha/include/asm/rwsem.h
index a83bbea62c67..0131a7058778 100644
--- a/arch/alpha/include/asm/rwsem.h
+++ b/arch/alpha/include/asm/rwsem.h
@@ -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
*/
diff --git a/arch/ia64/include/asm/rwsem.h b/arch/ia64/include/asm/rwsem.h
index ce112472bdd6..8b23e070b844 100644
--- a/arch/ia64/include/asm/rwsem.h
+++ b/arch/ia64/include/asm/rwsem.h
@@ -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
*/
diff --git a/arch/s390/include/asm/rwsem.h b/arch/s390/include/asm/rwsem.h
index fead491dfc28..c75e4471e618 100644
--- a/arch/s390/include/asm/rwsem.h
+++ b/arch/s390/include/asm/rwsem.h
@@ -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;
}
/*
diff --git a/arch/sh/include/asm/Kbuild b/arch/sh/include/asm/Kbuild
index a319745a7b63..751c3373a92c 100644
--- a/arch/sh/include/asm/Kbuild
+++ b/arch/sh/include/asm/Kbuild
@@ -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
diff --git a/arch/sh/include/asm/rwsem.h b/arch/sh/include/asm/rwsem.h
deleted file mode 100644
index edab57265293..000000000000
--- a/arch/sh/include/asm/rwsem.h
+++ /dev/null
@@ -1,132 +0,0 @@
-/*
- * 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 */
diff --git a/arch/sparc/include/asm/Kbuild b/arch/sparc/include/asm/Kbuild
index e928618838bc..6024c26c0585 100644
--- a/arch/sparc/include/asm/Kbuild
+++ b/arch/sparc/include/asm/Kbuild
@@ -16,6 +16,7 @@ generic-y += mm-arch-hooks.h
generic-y += module.h
generic-y += mutex.h
generic-y += preempt.h
+generic-y += rwsem.h
generic-y += serial.h
generic-y += trace_clock.h
generic-y += types.h
diff --git a/arch/sparc/include/asm/rwsem.h b/arch/sparc/include/asm/rwsem.h
deleted file mode 100644
index 069bf4d663a1..000000000000
--- a/arch/sparc/include/asm/rwsem.h
+++ /dev/null
@@ -1,124 +0,0 @@
-/*
- * rwsem.h: R/W semaphores implemented using CAS
- *
- * Written by David S. Miller (davem@redhat.com), 2001.
- * Derived from asm-i386/rwsem.h
- */
-#ifndef _SPARC64_RWSEM_H
-#define _SPARC64_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 0x00000000L
-#define RWSEM_ACTIVE_BIAS 0x00000001L
-#define RWSEM_ACTIVE_MASK 0xffffffffL
-#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
-#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 (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L))
- rwsem_down_read_failed(sem);
-}
-
-static inline int __down_read_trylock(struct rw_semaphore *sem)
-{
- long tmp;
-
- while ((tmp = sem->count) >= 0L) {
- if (tmp == cmpxchg(&sem->count, tmp,
- tmp + RWSEM_ACTIVE_READ_BIAS)) {
- return 1;
- }
- }
- return 0;
-}
-
-/*
- * lock for writing
- */
-static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
-{
- long tmp;
-
- tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS,
- (atomic64_t *)(&sem->count));
- if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
- rwsem_down_write_failed(sem);
-}
-
-static inline void __down_write(struct rw_semaphore *sem)
-{
- __down_write_nested(sem, 0);
-}
-
-static inline int __down_write_trylock(struct rw_semaphore *sem)
-{
- long tmp;
-
- tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
- RWSEM_ACTIVE_WRITE_BIAS);
- return tmp == RWSEM_UNLOCKED_VALUE;
-}
-
-/*
- * unlock after reading
- */
-static inline void __up_read(struct rw_semaphore *sem)
-{
- long tmp;
-
- tmp = atomic64_dec_return((atomic64_t *)(&sem->count));
- if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L))
- rwsem_wake(sem);
-}
-
-/*
- * unlock after writing
- */
-static inline void __up_write(struct rw_semaphore *sem)
-{
- if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
- (atomic64_t *)(&sem->count)) < 0L))
- rwsem_wake(sem);
-}
-
-/*
- * implement atomic add functionality
- */
-static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
-{
- atomic64_add(delta, (atomic64_t *)(&sem->count));
-}
-
-/*
- * downgrade write lock to read lock
- */
-static inline void __downgrade_write(struct rw_semaphore *sem)
-{
- long tmp;
-
- tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count));
- if (tmp < 0L)
- rwsem_downgrade_wake(sem);
-}
-
-/*
- * implement exchange and add functionality
- */
-static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
-{
- return atomic64_add_return(delta, (atomic64_t *)(&sem->count));
-}
-
-#endif /* __KERNEL__ */
-
-#endif /* _SPARC64_RWSEM_H */
diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index ceec86eb68e9..453744c1d347 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -99,26 +99,36 @@ 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)
+#define ____down_write(sem, slow_path) \
+({ \
+ long tmp; \
+ struct rw_semaphore* ret; \
+ asm volatile("# beginning down_write\n\t" \
+ LOCK_PREFIX " xadd %1,(%3)\n\t" \
+ /* adds 0xffff0001, returns the old value */ \
+ " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \
+ /* was the active mask 0 before? */\
+ " jz 1f\n" \
+ " call " slow_path "\n" \
+ "1:\n" \
+ "# ending down_write" \
+ : "+m" (sem->count), "=d" (tmp), "=a" (ret) \
+ : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \
+ : "memory", "cc"); \
+ ret; \
+})
+
+static inline void __down_write(struct rw_semaphore *sem)
{
- long tmp;
- asm volatile("# beginning down_write\n\t"
- LOCK_PREFIX " xadd %1,(%2)\n\t"
- /* adds 0xffff0001, returns the old value */
- " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t"
- /* was the active mask 0 before? */
- " jz 1f\n"
- " call call_rwsem_down_write_failed\n"
- "1:\n"
- "# ending down_write"
- : "+m" (sem->count), "=d" (tmp)
- : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS)
- : "memory", "cc");
+ ____down_write(sem, "call_rwsem_down_write_failed");
}
-static inline void __down_write(struct rw_semaphore *sem)
+static inline int __down_write_killable(struct rw_semaphore *sem)
{
- __down_write_nested(sem, 0);
+ if (IS_ERR(____down_write(sem, "call_rwsem_down_write_failed_killable")))
+ return -EINTR;
+
+ return 0;
}
/*
diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S
index be110efa0096..bf2c6074efd2 100644
--- a/arch/x86/lib/rwsem.S
+++ b/arch/x86/lib/rwsem.S
@@ -29,8 +29,10 @@
* there is contention on the semaphore.
*
* %eax contains the semaphore pointer on entry. Save the C-clobbered
- * registers (%eax, %edx and %ecx) except %eax whish is either a return
- * value or just clobbered..
+ * registers (%eax, %edx and %ecx) except %eax which is either a return
+ * value or just gets clobbered. Same is true for %edx so make sure GCC
+ * reloads it after the slow path, by making it hold a temporary, for
+ * example see ____down_write().
*/
#define save_common_regs \
@@ -106,6 +108,16 @@ ENTRY(call_rwsem_down_write_failed)
ret
ENDPROC(call_rwsem_down_write_failed)
+ENTRY(call_rwsem_down_write_failed_killable)
+ FRAME_BEGIN
+ save_common_regs
+ movq %rax,%rdi
+ call rwsem_down_write_failed_killable
+ restore_common_regs
+ FRAME_END
+ ret
+ENDPROC(call_rwsem_down_write_failed_killable)
+
ENTRY(call_rwsem_wake)
FRAME_BEGIN
/* do nothing if still outstanding active readers */
diff --git a/arch/xtensa/include/asm/Kbuild b/arch/xtensa/include/asm/Kbuild
index b56855a1382a..28cf4c5d65ef 100644
--- a/arch/xtensa/include/asm/Kbuild
+++ b/arch/xtensa/include/asm/Kbuild
@@ -22,6 +22,7 @@ generic-y += mm-arch-hooks.h
generic-y += percpu.h
generic-y += preempt.h
generic-y += resource.h
+generic-y += rwsem.h
generic-y += sections.h
generic-y += siginfo.h
generic-y += statfs.h
diff --git a/arch/xtensa/include/asm/rwsem.h b/arch/xtensa/include/asm/rwsem.h
deleted file mode 100644
index 249619e7e7f2..000000000000
--- a/arch/xtensa/include/asm/rwsem.h
+++ /dev/null
@@ -1,131 +0,0 @@
-/*
- * include/asm-xtensa/rwsem.h
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Largely copied from include/asm-ppc/rwsem.h
- *
- * Copyright (C) 2001 - 2005 Tensilica Inc.
- */
-
-#ifndef _XTENSA_RWSEM_H
-#define _XTENSA_RWSEM_H
-
-#ifndef _LINUX_RWSEM_H
-#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
-#endif
-
-#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_add_return(1,(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_sub_return(1,(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);
-}
-
-/*
- * 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 /* _XTENSA_RWSEM_H */