releases/3.4.24/workqueue-convert-bug_on-s-in-__queue_delayed_work-to-warn_on_once-s.patch

   1 From fc4b514f2727f74a4587c31db87e0e93465518c3 Mon Sep 17 00:00:00 2001
   2 From: Tejun Heo <tj@kernel.org>
   3 Date: Tue, 4 Dec 2012 07:40:39 -0800
   4 Subject: workqueue: convert BUG_ON()s in __queue_delayed_work() to WARN_ON_ONCE()s
   5
   6 From: Tejun Heo <tj@kernel.org>
   7
   8 commit fc4b514f2727f74a4587c31db87e0e93465518c3 upstream.
   9
  10 8852aac25e ("workqueue: mod_delayed_work_on() shouldn't queue timer on
  11 0 delay") unexpectedly uncovered a very nasty abuse of delayed_work in
  12 megaraid - it allocated work_struct, casted it to delayed_work and
  13 then pass that into queue_delayed_work().
  14
  15 Previously, this was okay because 0 @delay short-circuited to
  16 queue_work() before doing anything with delayed_work.  8852aac25e
  17 moved 0 @delay test into __queue_delayed_work() after sanity check on
  18 delayed_work making megaraid trigger BUG_ON().
  19
  20 Although megaraid is already fixed by c1d390d8e6 ("megaraid: fix
  21 BUG_ON() from incorrect use of delayed work"), this patch converts
  22 BUG_ON()s in __queue_delayed_work() to WARN_ON_ONCE()s so that such
  23 abusers, if there are more, trigger warning but don't crash the
  24 machine.
  25
  26 Signed-off-by: Tejun Heo <tj@kernel.org>
  27 Cc: Xiaotian Feng <xtfeng@gmail.com>
  28 Signed-off-by: Shuah Khan <shuah.khan@hp.com>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30
  31 ---
  32  kernel/workqueue.c |    4 ++--
  33  1 file changed, 2 insertions(+), 2 deletions(-)
  34
  35 --- a/kernel/workqueue.c
  36 +++ b/kernel/workqueue.c
  37 @@ -1141,8 +1141,8 @@ int queue_delayed_work_on(int cpu, struc
  38         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
  39                 unsigned int lcpu;
  40
  41 -               BUG_ON(timer_pending(timer));
  42 -               BUG_ON(!list_empty(&work->entry));
  43 +               WARN_ON_ONCE(timer_pending(timer));
  44 +               WARN_ON_ONCE(!list_empty(&work->entry));
  45
  46                 timer_stats_timer_set_start_info(&dwork->timer);
  47