Commit-ID: 802702e0c2618465b813242d4dfee6a233ba0beb Gitweb: http://git.kernel.org/tip/802702e0c2618465b813242d4dfee6a233ba0beb Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Fri, 12 Mar 2010 20:13:23 +0100 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Fri, 12 Mar 2010 22:40:44 +0100 timer: Try to survive timer callback preempt_count leak If a timer callback leaks preempt_count we currently assert a BUG(). That makes it unnecessarily hard to retrieve information about the problem especially on laptops and headless stations. There is a decent chance to survive the preempt_count leak by restoring the preempt_count to the value before the callback. That allows in many cases to get valuable information about the root cause of the problem. We carried that fixup in preempt-rt for years and were able to decode such wreckage quite a few times. Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Linux Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Arjan van de Veen <arjan@xxxxxxxxxxxxx> --- kernel/timer.c | 12 +++++++++--- 1 files changed, 9 insertions(+), 3 deletions(-) diff --git a/kernel/timer.c b/kernel/timer.c index 4522969..7e12e7b 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -982,9 +982,15 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long), lock_map_release(&lockdep_map); if (preempt_count != preempt_count()) { - printk(KERN_ERR "timer: %pF preempt leak: %08x -> %08x\n", - fn, preempt_count, preempt_count()); - BUG(); + WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n", + fn, preempt_count, preempt_count()); + /* + * Restore the preempt count. That gives us a decent + * chance to survive and extract information. If the + * callback kept a lock held, bad luck, but not worse + * than the BUG() we had. + */ + preempt_count() = preempt_count; } } -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html