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authorMike Waychison <mikew@google.com>2005-09-30 00:01:27 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-29 15:41:42 -0700
commit7644143cd6f7e029f3a8ea64f5fb0ab33ec39f72 (patch)
tree253112e894c11c37a52ac93fe0f470fe990c2c18 /arch/x86_64
parent7d318d774789657c37a5e994a4a2cf59d4879ae7 (diff)
downloadop-kernel-dev-7644143cd6f7e029f3a8ea64f5fb0ab33ec39f72.zip
op-kernel-dev-7644143cd6f7e029f3a8ea64f5fb0ab33ec39f72.tar.gz
[PATCH] x86_64: Fix mce_log
The attempt to fixup the lockless mce log buffer introduced an infinite loop when trying to find a free entry. And: Using rcu_dereference() to load mcelog.next doesn't seem to be sufficient enough to ensure that mcelog.next is loaded each time around the loop in mce_log(). Instead, use an explicit rmb() to ensure that the compiler gets it right. AK: turned the smp_wmbs into true wmbs to make sure they are not reordered by the compiler on UP. Signed-off-by: Mike Waychison <mikew@google.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/x86_64')
-rw-r--r--arch/x86_64/kernel/mce.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/arch/x86_64/kernel/mce.c b/arch/x86_64/kernel/mce.c
index 08203b0..69541db 100644
--- a/arch/x86_64/kernel/mce.c
+++ b/arch/x86_64/kernel/mce.c
@@ -54,9 +54,12 @@ void mce_log(struct mce *mce)
{
unsigned next, entry;
mce->finished = 0;
- smp_wmb();
+ wmb();
for (;;) {
entry = rcu_dereference(mcelog.next);
+ /* The rmb forces the compiler to reload next in each
+ iteration */
+ rmb();
for (;;) {
/* When the buffer fills up discard new entries. Assume
that the earlier errors are the more interesting. */
@@ -69,6 +72,7 @@ void mce_log(struct mce *mce)
entry++;
continue;
}
+ break;
}
smp_rmb();
next = entry + 1;
@@ -76,9 +80,9 @@ void mce_log(struct mce *mce)
break;
}
memcpy(mcelog.entry + entry, mce, sizeof(struct mce));
- smp_wmb();
+ wmb();
mcelog.entry[entry].finished = 1;
- smp_wmb();
+ wmb();
if (!test_and_set_bit(0, &console_logged))
notify_user = 1;
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