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[Bug runtime/6487] kernel.function("internal_add_timer") freezes system.
- From: "joshua dot i dot stone at intel dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 7 May 2008 18:48:18 -0000
- Subject: [Bug runtime/6487] kernel.function("internal_add_timer") freezes system.
- References: <20080507143402.6487.mhiramat@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From joshua dot i dot stone at intel dot com 2008-05-07 18:48 -------
It's just a coincidence that the first mod_timer was also from stap. There's a
real bug here: a probe on the internals of __mod_timer will call
stp_print_flush, and if the buffer is full it will end up calling __mod_timer
again and cause a deadlock.
relay_switch_subbuf has this note:
> /*
> * Calling wake_up_interruptible() from here
> * will deadlock if we happen to be logging
> * from the scheduler (trying to re-grab
> * rq->lock), so defer it.
> */
> __mod_timer(&buf->timer, jiffies + 1);
... but in this case we happen to be logging from within __mod_timer, so it's a
new deadlock.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=6487
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