Re: Soft lockup issue in Linux 4.1.9

On Thu, 1 Oct 2015, Eric Dumazet wrote:

On Thu, Oct 1, 2015 at 4:43 AM, Holger Hoffstätte
[off-list ref] wrote:

quoted

On 10/01/15 13:29, Eric Dumazet wrote:

quoted

quoted

commit 83fccfc3940c4a2db90fd7e7079f5b465cd8c6af
Author: Eric Dumazet [off-list ref]
Date:   Thu Aug 13 15:44:51 2015 -0700

    inet: fix potential deadlock in reqsk_queue_unlink()

    When replacing del_timer() with del_timer_sync(), I introduced
    a deadlock condition :

    reqsk_queue_unlink() is called from inet_csk_reqsk_queue_drop()

    inet_csk_reqsk_queue_drop() can be called from many contexts,
    one being the timer handler itself (reqsk_timer_handler()).

    In this case, del_timer_sync() loops forever.

    Simple fix is to test if timer is pending.

    Fixes: 2235f2ac75fd ("inet: fix races with reqsk timers")
    Signed-off-by: Eric Dumazet [off-list ref]
    Signed-off-by: David S. Miller [off-list ref]

Whohoo! It applies/builds cleanly to 4.1.10-rc1 and is running as
we speak. Let's hope that this fixes the lockups.

It definitely should help !

What makes sure, that the timer cannot be readded while that timer
callback is running?

Thanks,

	tglx