Re: next-20081119: general protection fault: get_next_timer_interrupt()

Mike Anderson
2008-11-24T21:35:32Z

Thomas Gleixner <tglx@linutronix.de> wrote:
> > Well, not sure. Most likely candidate is the new block timer code.
> > What seems to be happening is that the queue is being released with
> > either an outstanding request (refcounting problem) or ticking timer
> > with no work (block timer problem). The way scanning works is that we
> > create a request queue for each device we probe and then delete it again
> > if nothing appears after the bus settle time. The argument against
> > this is that it should show up on every scanned bus. However, these are
> > getting rarer; I was just about to write that I hadn't seen it when I
> > remembered that all my SCSI testing systems are currently running
> > hotplug reporting busses (i.e. don't do scanning). However,
> > fortunately, I've also booted voyager recently which does use parallel
> > SCSI and doesn't see this either, so it could also be megaraid_sas
> > specific.
>
> Yeah, block could it be as well. Jens, Mike ?

I added a comment to bug 12020 on Thursday about a few other systems that
where seeing the signature shown in bug 12020. It appeared from debug that
there where a few paths that where adding timers for requests that where
not expected.

http://bugzilla.kernel.org/show_bug.cgi?id=12020

It would be good to know if the debug patch below effects your problem as while.

If it does we need to investigated a solution to resolve not adding a
timer for these requests.

-andmike
--
Michael Anderson
andmike@linux.vnet.ibm.com

blk: blk_add_timer debug patch

[DEBUG] Debug only patch.

Debug patch to blk_add_timer to not start timer for request that do not
have the REQ_STARTED flag set.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
---
block/blk-timeout.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/block/blk-timeout.c b/block/blk-timeout.c
index 69185ea..4389391 100644
--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -177,6 +177,9 @@ void blk_add_timer(struct request *req)
BUG_ON(!list_empty(&req->timeout_list));
BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));

+ if (!(req->cmd_flags & REQ_STARTED))
+ return;
+
if (req->timeout)
req->deadline = jiffies + req->timeout;
else {
--
1.5.6.5