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xen/blkback: Fix two races in the handling of barrier requests. 

There are two windows of opportunity to cause a race when
processing a barrier request. This patch fixes this.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2011-10-17 14:27:48 -04:00
parent dda1852802
commit 6927d92091
1 changed files with 5 additions and 5 deletions
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10
drivers/block/xen-blkback/blkback.c
View File

@ -456,15 +456,15 @@ static void xen_blk_drain_io(struct xen_blkif *blkif)
{
atomic_set(&blkif->drain, 1);
do {
/* The initial value is one, and one refcnt taken at the
* start of the xen_blkif_schedule thread. */
if (atomic_read(&blkif->refcnt) <= 2)
break;
wait_for_completion_interruptible_timeout(
&blkif->drain_complete, HZ);
if (!atomic_read(&blkif->drain))
break;
/* The initial value is one, and one refcnt taken at the
* start of the xen_blkif_schedule thread. */
if (atomic_read(&blkif->refcnt) <= 2)
break;
} while (!kthread_should_stop());
atomic_set(&blkif->drain, 0);
}
@ -502,11 +502,11 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
make_response(pending_req->blkif, pending_req->id,
pending_req->operation, pending_req->status);
xen_blkif_put(pending_req->blkif);
free_req(pending_req);
if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
if (atomic_read(&pending_req->blkif->drain))
complete(&pending_req->blkif->drain_complete);
}
free_req(pending_req);
}
}