Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f3da54ba140c6427fa4a32913e1bf406f41b5dda
Commit: f3da54ba140c6427fa4a32913e1bf406f41b5dda
Parent: 9ca2152e173554e7ffb7919dc4916a7c61f8be1a
Author: Jens Axboe <[EMAIL PROTECTED]>
AuthorDate: Thu Sep 13 14:26:53 2007 +0200
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Sep 13 08:20:25 2007 -0700
Fix race with shared tag queue maps
There's a race condition in blk_queue_end_tag() for shared tag maps,
users include stex (promise supertrak thingy) and qla2xxx. The former
at least has reported bugs in this area, not sure why we haven't seen
any for the latter. It could be because the window is narrow and that
other conditions in the qla2xxx code hide this. It's a real bug,
though, as the stex smp users can attest.
We need to ensure two things - the tag bit clearing needs to happen
AFTER we cleared the tag pointer, as the tag bit clearing/setting is
what protects this map. Secondly, we need to ensure that the visibility
of the tag pointer and tag bit clear are ordered properly.
[ I removed the SMP barriers - "test_and_clear_bit()" already implies
all the required barriers. -- Linus ]
Also see http://bugzilla.kernel.org/show_bug.cgi?id=7842
Signed-off-by: Jens Axboe <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
block/ll_rw_blk.c | 13 +++++++------
1 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index a15845c..cd20367 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1075,12 +1075,6 @@ void blk_queue_end_tag(struct request_queue *q, struct
request *rq)
*/
return;
- if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
- printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
- __FUNCTION__, tag);
- return;
- }
-
list_del_init(&rq->queuelist);
rq->cmd_flags &= ~REQ_QUEUED;
rq->tag = -1;
@@ -1090,6 +1084,13 @@ void blk_queue_end_tag(struct request_queue *q, struct
request *rq)
__FUNCTION__, tag);
bqt->tag_index[tag] = NULL;
+
+ if (unlikely(!test_and_clear_bit(tag, bqt->tag_map))) {
+ printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
+ __FUNCTION__, tag);
+ return;
+ }
+
bqt->busy--;
}
-
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