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    SubjectRe: next-20081119: general protection fault: get_next_timer_interrupt()
    On Tue, Nov 25 2008, Alexander Beregalov wrote:
    > 2008/11/25 <malahal@us.ibm.com>:
    > > Jens Axboe [jens.axboe@oracle.com] wrote:
    > >> On Mon, Nov 24 2008, malahal@us.ibm.com wrote:
    > >> > Stephen Rothwell [sfr@canb.auug.org.au] wrote:
    > >> > > > The block timer code calls del_timer(), should it call del_timer_sync()?
    > >> > > > It is possible although unlikely that you are hitting del_timer_sync vs
    > >> > > > del_timer problem in the block timeout code. Can only be seen on SMP
    > >> > > > systems though!
    > >> > >
    > >> > > Is this still a problem in next-20081121? In that tree, the block commit
    > >> > > "block: leave the request timeout timer running even on an empty list"
    > >> > > was changed to add this:
    > >> > >
    > >> > > diff --git a/block/blk-core.c b/block/blk-core.c
    > >> > > index 04267d6..44f547c 100644
    > >> > > --- a/block/blk-core.c
    > >> > > +++ b/block/blk-core.c
    > >> > > @@ -391,6 +391,7 @@ EXPORT_SYMBOL(blk_stop_queue);
    > >> > > void blk_sync_queue(struct request_queue *q)
    > >> > > {
    > >> > > del_timer_sync(&q->unplug_timer);
    > >> > > + del_timer_sync(&q->timeout);
    > >> > > kblockd_flush_work(&q->unplug_work);
    > >> > > }
    > >> > > EXPORT_SYMBOL(blk_sync_queue);
    > >> >
    > >> > I was looking at the Linux tree. Clearly same problem doesn't exist with
    > >> > the above commit! I wonder why kblockd_flush_work() is called after the
    > >> > del_timer_sync(). It makes sense to cancel the work and then shutdown
    > >> > the timer(s). I doubt if you are running into this problem though.
    > >>
    > >> If the kernel tested doesn't include the above fix, it'll surely go
    > >> boom. Can someone verify that this is the case?
    > >
    > > Just looked, next-20081119 doesn't have the above fix. It is included in
    > > next-20081120. Also note that the above fix is only partially copied,
    > > there is other part that removed deleting the timer when there are no
    > > outstanding requests.
    > >
    > Yes, I can not reproduce it anymore on linux-next 1121 and newer. (I
    > did not try 1120) It seems the fix works pretty good. Is it still
    > needed and reasonable to investigate the problem on next-20081119?
    > Unfortunately I do not have much time for it.

    No, you don't have to investigate further. This was a known bug that is
    fixed in -next and mainline basically right after next-20081119.

    >
    > All these problems have gone away on next-1125 except ODEBUG warning
    > on HPET.

    --
    Jens Axboe



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