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| author | David S. Miller <davem@davemloft.net> | 2016-01-13 00:21:27 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-01-13 00:21:27 -0500 |
| commit | ddb5388ffd0ad75d07e7b78181a0b579824ba6f0 (patch) | |
| tree | be1e2bd103c69d7bbace3fffd97bc3d714bbc3d7 /include/linux/compiler.h | |
| parent | ccdf6ce6a8dba374668ae9b4d763e19903611c38 (diff) | |
| parent | 67990608c8b95d2b8ccc29932376ae73d5818727 (diff) | |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 4dac1036594f..00b042c49ccd 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -299,6 +299,23 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s __u.__val; \ }) +/** + * smp_cond_acquire() - Spin wait for cond with ACQUIRE ordering + * @cond: boolean expression to wait for + * + * Equivalent to using smp_load_acquire() on the condition variable but employs + * the control dependency of the wait to reduce the barrier on many platforms. + * + * The control dependency provides a LOAD->STORE order, the additional RMB + * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order, + * aka. ACQUIRE. + */ +#define smp_cond_acquire(cond) do { \ + while (!(cond)) \ + cpu_relax(); \ + smp_rmb(); /* ctrl + rmb := acquire */ \ +} while (0) + #endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ |