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ARC: ensure futex ops are atomic in !LLSC config

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W/o hardware assisted atomic r-m-w the best we can do is to disable
preemption.

Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michel Lespinasse <walken@google.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2015-08-06 19:11:06 +05:30
parent 5e0574292a
commit eb2cd8b72b
1 changed files with 12 additions and 0 deletions
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12
arch/arc/include/asm/futex.h
View file

@ -87,6 +87,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;
#ifndef CONFIG_ARC_HAS_LLSC
preempt_disable(); /* to guarantee atomic r-m-w of futex op */
#endif
pagefault_disable();
switch (op) {
@ -111,6 +114,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
}
pagefault_enable();
#ifndef CONFIG_ARC_HAS_LLSC
preempt_enable();
#endif
if (!ret) {
switch (cmp) {
@ -153,6 +159,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval,
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
#ifndef CONFIG_ARC_HAS_LLSC
preempt_disable(); /* to guarantee atomic r-m-w of futex op */
#endif
smp_mb();
__asm__ __volatile__(
@ -182,6 +191,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval,
smp_mb();
#ifndef CONFIG_ARC_HAS_LLSC
preempt_enable();
#endif
*uval = existval;
return ret;
}