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authorHugh Dickins <hugh@veritas.com>2006-10-31 18:41:51 +0000
committerPaul Mackerras <paulus@samba.org>2006-11-01 14:52:49 +1100
commit292f86f005e3867277b2126c2399eea3e773a4fc (patch)
tree12a7040e81b80f87f4c0899b94dd8bd29c1df391 /arch/powerpc/lib
parent96268889ee369b36203b7a06e8aabb197270216e (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 'arch/powerpc/lib')
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