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authorWill Deacon <will.deacon@arm.com>2016-06-27 19:43:54 +0200
committerIngo Molnar <mingo@kernel.org>2016-07-07 09:10:53 +0200
commit03e3c2b7edbe1e8758196b2c7843333eb328063d (patch)
treef894288a88daa7d20fc00be4f294a1344ae2601e /arch/arm64/include/asm/barrier.h
parentlocking/static_keys: Fix non static symbol Sparse warning (diff)
downloadlinux-03e3c2b7edbe1e8758196b2c7843333eb328063d.tar.xz
linux-03e3c2b7edbe1e8758196b2c7843333eb328063d.zip
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.h13
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__ */