diff options
| author | Will Deacon <will.deacon@arm.com> | 2016-06-27 18:43:54 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-07-07 09:10:53 +0200 |
| commit | 03e3c2b7edbe1e8758196b2c7843333eb328063d (patch) | |
| tree | f894288a88daa7d20fc00be4f294a1344ae2601e /arch/arm64/include/asm/barrier.h | |
| parent | 885885f6b88d22f81e67ee6a61561e480b27d27a (diff) | |
locking/barriers, arch/arm64: Implement LDXR+WFE based smp_cond_load_acquire()
smp_cond_load_acquire() is used to spin on a variable until some
expression involving that variable becomes true.
On arm64, we can build this using the LDXR and WFE instructions, since
clearing of the exclusive monitor as a result of the variable being
changed by another CPU generates an event, which will wake us up out of WFE.
This patch implements smp_cond_load_acquire() using LDXR and WFE, which
themselves are contained in an internal __cmpwait() function.
Signed-off-by: Will Deacon <will.deacon@arm.com>
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: catalin.marinas@arm.com
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1467049434-30451-1-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/arm64/include/asm/barrier.h')
| -rw-r--r-- | arch/arm64/include/asm/barrier.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h index dae5c49618db..4eea7f618dce 100644 --- a/arch/arm64/include/asm/barrier.h +++ b/arch/arm64/include/asm/barrier.h @@ -91,6 +91,19 @@ do { \ __u.__val; \ }) +#define smp_cond_load_acquire(ptr, cond_expr) \ +({ \ + typeof(ptr) __PTR = (ptr); \ + typeof(*ptr) VAL; \ + for (;;) { \ + VAL = smp_load_acquire(__PTR); \ + if (cond_expr) \ + break; \ + __cmpwait_relaxed(__PTR, VAL); \ + } \ + VAL; \ +}) + #include <asm-generic/barrier.h> #endif /* __ASSEMBLY__ */ |