On Thu, Nov 03, 2011 at 05:08:40PM +0100, Jiri Slaby wrote: > Hi, > > I'm seeing the NULL ptr dereference below on each boot of KVM virtual > machine. q->elevator is NULL. This is next-20111025. > > I tried to apply Tejun's patch from: > https://lkml.org/lkml/2011/4/30/87 > but it doesn't help. Maybe I should revert something? > > Scanning for LVM volume groups... > Reading all physical volumes. This may take a while... > No volume groups found > BUG: unable to handle kernel NULL pointer dereference at (null) > IP: [<ffffffff8125a69c>] elv_drain_elevator+0x1c/0x70 > PGD 46176067 PUD 452b5067 PMD 0 > Oops: 0000 [#1] SMP > CPU 0 > Modules linked in: > > Pid: 830, comm: kworker/0:2 Not tainted 3.1.0-next-20111025_64+ #1590 > Bochs Bochs > RIP: 0010:[<ffffffff8125a69c>] [<ffffffff8125a69c>] > elv_drain_elevator+0x1c/0x70 Heh, probably md is tearing down a queue which isn't fully setup. Does the following fix the problem? Thanks. diff --git a/block/blk-core.c b/block/blk-core.c index f658711..5292e31 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -408,7 +408,8 @@ void blk_cleanup_queue(struct request_queue *q) mutex_unlock(&q->sysfs_lock); /* drain all requests queued before DEAD marking */ - blk_drain_queue(q, true); + if (q->elevator) + blk_drain_queue(q, true); /* @q won't process any more request, flush async actions */ del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer); -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
