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locking/spinlock, arch: Update and fix spin_unlock_wait() implementations 

This patch updates/fixes all spin_unlock_wait() implementations.

The update is in semantics; where it previously was only a control
dependency, we now upgrade to a full load-acquire to match the
store-release from the spin_unlock() we waited on. This ensures that
when spin_unlock_wait() returns, we're guaranteed to observe the full
critical section we waited on.

This fixes a number of spin_unlock_wait() users that (not
unreasonably) rely on this.

I also fixed a number of ticket lock versions to only wait on the
current lock holder, instead of for a full unlock, as this is
sufficient.

Furthermore; again for ticket locks; I added an smp_rmb() in between
the initial ticket load and the spin loop testing the current value
because I could not convince myself the address dependency is
sufficient, esp. if the loads are of different sizes.

I'm more than happy to remove this smp_rmb() again if people are
certain the address dependency does indeed work as expected.

Note: PPC32 will be fixed independently

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: chris@zankel.net
Cc: cmetcalf@mellanox.com
Cc: davem@davemloft.net
Cc: dhowells@redhat.com
Cc: james.hogan@imgtec.com
Cc: jejb@parisc-linux.org
Cc: linux@armlinux.org.uk
Cc: mpe@ellerman.id.au
Cc: ralf@linux-mips.org
Cc: realmz6@gmail.com
Cc: rkuo@codeaurora.org
Cc: rth@twiddle.net
Cc: schwidefsky@de.ibm.com
Cc: tony.luck@intel.com
Cc: vgupta@synopsys.com
Cc: ysato@users.sourceforge.jp
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-05-26 10:35:03 +02:00 committed by Ingo Molnar
parent b464d1270a
commit 726328d92a
20 changed files with 145 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/alpha/include/asm/spinlock.h
View File

@ -3,6 +3,8 @@
#include <linux/kernel.h>
#include <asm/current.h>
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* Simple spin lock operations. There are two variants, one clears IRQ's
@ -13,8 +15,11 @@
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_is_locked(x) ((x)->lock != 0)
#define arch_spin_unlock_wait(x) \
do { cpu_relax(); } while ((x)->lock)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->lock, !VAL);
}
static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{

7
arch/arc/include/asm/spinlock.h
View File

@ -15,8 +15,11 @@
#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_unlock_wait(x) \
do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->slock, !VAL);
}
#ifdef CONFIG_ARC_HAS_LLSC

19
arch/arm/include/asm/spinlock.h
View File

@ -6,6 +6,8 @@
#endif
#include <linux/prefetch.h>
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* sev and wfe are ARMv6K extensions. Uniprocessor ARMv6 may not have the K
@ -50,8 +52,21 @@ static inline void dsb_sev(void)
* memory.
*/
#define arch_spin_unlock_wait(lock) \
do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
u16 owner = READ_ONCE(lock->tickets.owner);
for (;;) {
arch_spinlock_t tmp = READ_ONCE(*lock);
if (tmp.tickets.owner == tmp.tickets.next ||
tmp.tickets.owner != owner)
break;
wfe();
}
smp_acquire__after_ctrl_dep();
}
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

5
arch/blackfin/include/asm/spinlock.h
View File

@ -12,6 +12,8 @@
#else
#include <linux/atomic.h>
#include <asm/processor.h>
#include <asm/barrier.h>
asmlinkage int __raw_spin_is_locked_asm(volatile int *ptr);
asmlinkage void __raw_spin_lock_asm(volatile int *ptr);
@ -48,8 +50,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
while (arch_spin_is_locked(lock))
cpu_relax();
smp_cond_load_acquire(&lock->lock, !VAL);
}
static inline int arch_read_can_lock(arch_rwlock_t *rw)

10
arch/hexagon/include/asm/spinlock.h
View File

@ -23,6 +23,8 @@
#define _ASM_SPINLOCK_H
#include <asm/irqflags.h>
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* This file is pulled in for SMP builds.
@ -176,8 +178,12 @@ static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
* SMP spinlocks are intended to allow only a single CPU at the lock
*/
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_unlock_wait(lock) \
do {while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->lock, !VAL);
}
#define arch_spin_is_locked(x) ((x)->lock != 0)
#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)

4
arch/ia64/include/asm/spinlock.h
View File

@ -15,6 +15,8 @@
#include <linux/atomic.h>
#include <asm/intrinsics.h>
#include <asm/barrier.h>
#include <asm/processor.h>
#define arch_spin_lock_init(x) ((x)->lock = 0)
@ -86,6 +88,8 @@ static __always_inline void __ticket_spin_unlock_wait(arch_spinlock_t *lock)
return;
cpu_relax();
}
smp_acquire__after_ctrl_dep();
}
static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)

9
arch/m32r/include/asm/spinlock.h
View File

@ -13,6 +13,8 @@
#include <linux/atomic.h>
#include <asm/dcache_clear.h>
#include <asm/page.h>
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* Your basic SMP spinlocks, allowing only a single CPU anywhere
@ -27,8 +29,11 @@
#define arch_spin_is_locked(x) (*(volatile int *)(&(x)->slock) <= 0)
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_unlock_wait(x) \
do { cpu_relax(); } while (arch_spin_is_locked(x))
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->slock, VAL > 0);
}
/**
* arch_spin_trylock - Try spin lock and return a result

14
arch/metag/include/asm/spinlock.h
View File

@ -1,14 +1,24 @@
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#include <asm/barrier.h>
#include <asm/processor.h>
#ifdef CONFIG_METAG_ATOMICITY_LOCK1
#include <asm/spinlock_lock1.h>
#else
#include <asm/spinlock_lnkget.h>
#endif
#define arch_spin_unlock_wait(lock) \
do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
/*
* both lock1 and lnkget are test-and-set spinlocks with 0 unlocked and 1
* locked.
*/
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->lock, !VAL);
}
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

19
arch/mips/include/asm/spinlock.h
View File

@ -12,6 +12,7 @@
#include <linux/compiler.h>
#include <asm/barrier.h>
#include <asm/processor.h>
#include <asm/compiler.h>
#include <asm/war.h>
@ -48,8 +49,22 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
}
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_unlock_wait(x) \
while (arch_spin_is_locked(x)) { cpu_relax(); }
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
u16 owner = READ_ONCE(lock->h.serving_now);
smp_rmb();
for (;;) {
arch_spinlock_t tmp = READ_ONCE(*lock);
if (tmp.h.serving_now == tmp.h.ticket ||
tmp.h.serving_now != owner)
break;
cpu_relax();
}
smp_acquire__after_ctrl_dep();
}
static inline int arch_spin_is_contended(arch_spinlock_t *lock)
{

8
arch/mn10300/include/asm/spinlock.h
View File

@ -12,6 +12,8 @@
#define _ASM_SPINLOCK_H
#include <linux/atomic.h>
#include <asm/barrier.h>
#include <asm/processor.h>
#include <asm/rwlock.h>
#include <asm/page.h>
@ -23,7 +25,11 @@
*/
#define arch_spin_is_locked(x) (*(volatile signed char *)(&(x)->slock) != 0)
#define arch_spin_unlock_wait(x) do { barrier(); } while (arch_spin_is_locked(x))
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->slock, !VAL);
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{

9
arch/parisc/include/asm/spinlock.h
View File

@ -13,8 +13,13 @@ static inline int arch_spin_is_locked(arch_spinlock_t *x)
}
#define arch_spin_lock(lock) arch_spin_lock_flags(lock, 0)
#define arch_spin_unlock_wait(x) \
do { cpu_relax(); } while (arch_spin_is_locked(x))
static inline void arch_spin_unlock_wait(arch_spinlock_t *x)
{
volatile unsigned int *a = __ldcw_align(x);
smp_cond_load_acquire(a, VAL);
}
static inline void arch_spin_lock_flags(arch_spinlock_t *x,
unsigned long flags)

3
arch/s390/include/asm/spinlock.h
View File

@ -10,6 +10,8 @@
#define __ASM_SPINLOCK_H
#include <linux/smp.h>
#include <asm/barrier.h>
#include <asm/processor.h>
#define SPINLOCK_LOCKVAL (S390_lowcore.spinlock_lockval)
@ -97,6 +99,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
while (arch_spin_is_locked(lock))
arch_spin_relax(lock);
smp_acquire__after_ctrl_dep();
}
/*

10
arch/sh/include/asm/spinlock.h
View File

@ -19,14 +19,20 @@
#error "Need movli.l/movco.l for spinlocks"
#endif
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* Your basic SMP spinlocks, allowing only a single CPU anywhere
*/
#define arch_spin_is_locked(x) ((x)->lock <= 0)
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_unlock_wait(x) \
do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->lock, VAL > 0);
}
/*
* Simple spin lock operations. There are two variants, one clears IRQ's

7
arch/sparc/include/asm/spinlock_32.h
View File

@ -9,12 +9,15 @@
#ifndef __ASSEMBLY__
#include <asm/psr.h>
#include <asm/barrier.h>
#include <asm/processor.h> /* for cpu_relax */
#define arch_spin_is_locked(lock) (*((volatile unsigned char *)(lock)) != 0)
#define arch_spin_unlock_wait(lock) \
do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->lock, !VAL);
}
static inline void arch_spin_lock(arch_spinlock_t *lock)
{

10
arch/sparc/include/asm/spinlock_64.h
View File

@ -8,6 +8,9 @@
#ifndef __ASSEMBLY__
#include <asm/processor.h>
#include <asm/barrier.h>
/* To get debugging spinlocks which detect and catch
* deadlock situations, set CONFIG_DEBUG_SPINLOCK
* and rebuild your kernel.
@ -23,9 +26,10 @@
#define arch_spin_is_locked(lp) ((lp)->lock != 0)
#define arch_spin_unlock_wait(lp) \
do { rmb(); \
} while((lp)->lock)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->lock, !VAL);
}
static inline void arch_spin_lock(arch_spinlock_t *lock)
{

6
arch/tile/lib/spinlock_32.c
View File

@ -76,6 +76,12 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock)
do {
delay_backoff(iterations++);
} while (READ_ONCE(lock->current_ticket) == curr);
/*
* The TILE architecture doesn't do read speculation; therefore
* a control dependency guarantees a LOAD->{LOAD,STORE} order.
*/
barrier();
}
EXPORT_SYMBOL(arch_spin_unlock_wait);

6
arch/tile/lib/spinlock_64.c
View File

@ -76,6 +76,12 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock)
do {
delay_backoff(iterations++);
} while (arch_spin_current(READ_ONCE(lock->lock)) == curr);
/*
* The TILE architecture doesn't do read speculation; therefore
* a control dependency guarantees a LOAD->{LOAD,STORE} order.
*/
barrier();
}
EXPORT_SYMBOL(arch_spin_unlock_wait);

10
arch/xtensa/include/asm/spinlock.h
View File

@ -11,6 +11,9 @@
#ifndef _XTENSA_SPINLOCK_H
#define _XTENSA_SPINLOCK_H
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* spinlock
*
@ -29,8 +32,11 @@
*/
#define arch_spin_is_locked(x) ((x)->slock != 0)
#define arch_spin_unlock_wait(lock) \
do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->slock, !VAL);
}
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

2
include/asm-generic/barrier.h
View File

@ -194,7 +194,7 @@ do { \
})
#endif
#endif
#endif /* CONFIG_SMP */
/* Barriers for virtual machine guests when talking to an SMP host */
#define virt_mb() __smp_mb()

10
include/linux/spinlock_up.h
View File

@ -6,6 +6,7 @@
#endif
#include <asm/processor.h> /* for cpu_relax() */
#include <asm/barrier.h>
/*
* include/linux/spinlock_up.h - UP-debug version of spinlocks.
@ -25,6 +26,11 @@
#ifdef CONFIG_DEBUG_SPINLOCK
#define arch_spin_is_locked(x) ((x)->slock == 0)
static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_cond_load_acquire(&lock->slock, VAL);
}
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
lock->slock = 0;
@ -67,6 +73,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
#else /* DEBUG_SPINLOCK */
#define arch_spin_is_locked(lock) ((void)(lock), 0)
#define arch_spin_unlock_wait(lock) do { barrier(); (void)(lock); } while (0)
/* for sched/core.c and kernel_lock.c: */
# define arch_spin_lock(lock) do { barrier(); (void)(lock); } while (0)
# define arch_spin_lock_flags(lock, flags) do { barrier(); (void)(lock); } while (0)
@ -79,7 +86,4 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
#define arch_read_can_lock(lock) (((void)(lock), 1))
#define arch_write_can_lock(lock) (((void)(lock), 1))
#define arch_spin_unlock_wait(lock) \
do { cpu_relax(); } while (arch_spin_is_locked(lock))
#endif /* __LINUX_SPINLOCK_UP_H */