diff options
| author | Hugh Dickins <hugh@veritas.com> | 2006-10-31 18:41:51 +0000 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2006-11-01 14:52:49 +1100 |
| commit | 292f86f005e3867277b2126c2399eea3e773a4fc (patch) | |
| tree | 12a7040e81b80f87f4c0899b94dd8bd29c1df391 /include/asm-powerpc | |
| parent | 96268889ee369b36203b7a06e8aabb197270216e (diff) | |
[POWERPC] Make mmiowb's io_sync preempt safe
If mmiowb() is always used prior to releasing spinlock as Doc suggests,
then it's safe against preemption; but I'm not convinced that's always
the case. If preemption occurs between sync and get_paca()->io_sync = 0,
I believe there's no problem. But in the unlikely event that gcc does
the store relative to another register than r13 (as it did with current),
then there's a small danger of setting another cpu's io_sync to 0, after
it had just set it to 1. Rewrite ppc64 mmiowb to prevent that.
The remaining io_sync assignments in io.h all get_paca()->io_sync = 1,
which is harmless even if preempted to the wrong cpu (the context switch
itself syncs); and those in spinlock.h are while preemption is disabled.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'include/asm-powerpc')
| -rw-r--r-- | include/asm-powerpc/io.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/include/asm-powerpc/io.h b/include/asm-powerpc/io.h index 3baff8b0fd5a..c2c5f14b5f5f 100644 --- a/include/asm-powerpc/io.h +++ b/include/asm-powerpc/io.h @@ -163,8 +163,11 @@ extern void _outsl_ns(volatile u32 __iomem *port, const void *buf, long count); static inline void mmiowb(void) { - __asm__ __volatile__ ("sync" : : : "memory"); - get_paca()->io_sync = 0; + unsigned long tmp; + + __asm__ __volatile__("sync; li %0,0; stb %0,%1(13)" + : "=&r" (tmp) : "i" (offsetof(struct paca_struct, io_sync)) + : "memory"); } /* |