Li Dongyang
2011-Sep-14 06:02 UTC
[Xen-devel] [PATCH] xen-blkfront: fix a deadlock while handling discard response
When we get EOPNOTSUPP response for a discard request, we will clear the discard flag on the request queue so we won''t attempt to send discard requests to backend again, and this should be protected under rq->queue_lock. However, when we setup the request queue, we pass blkif_io_lock to blk_init_queue so rq->queue_lock is blkif_io_lock indeed, and this lock is already taken when we are in blkif_interrpt, so remove the spin_lock/spin_unlock when we clear the discard flag or we will end up with deadlock here, Thanks Sorry for the stupid mistake. Signed-off-by: Li Dongyang <lidongyang@novell.com> --- drivers/block/xen-blkfront.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 86e2c63..d9789f18 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -747,9 +747,12 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) info->gd->disk_name); error = -EOPNOTSUPP; info->feature_discard = 0; - spin_lock(rq->queue_lock); + /* + * rq->queue_lock should be acquired before this call, + * it is actually blkif_io_lock, and already been taken + * once we are in blkif_interrupt + */ queue_flag_clear(QUEUE_FLAG_DISCARD, rq); - spin_unlock(rq->queue_lock); } __blk_end_request_all(req, error); break; -- 1.7.6.1 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel