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| author | Mark Brown <broonie@kernel.org> | 2016-02-09 18:20:39 +0000 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2016-02-09 18:20:39 +0000 |
| commit | fcdcc79628a1919bde9acf239e364f65bab6327c (patch) | |
| tree | 5499be387cf3028c90ac083b1cf866ebed7bf7e0 /include/linux/compiler.h | |
| parent | 7a8d44bc89e5cddcd5c0704a11a90484d36ba6ba (diff) | |
| parent | a0a90718f18264dc904d34a580f332006f5561e9 (diff) | |
Merge branch 'topic/acpi' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi into spi-pxa2xx
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__ */ |