On Wed, Aug 15, 2012 at 03:47:33PM -0400, Paul Gortmaker wrote:
> From: John Stultz <john.stu...@linaro.org>
>
> -------------------
> This is a commit scheduled for the next v2.6.34 longterm release.
> http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
> If you see a problem with using this for longterm, please comment.
> -------------------
>
> commit 6b43ae8a619d17c4935c3320d2ef9e92bdeed05d upstream.
>
> This should have been backported when it was commited, but I
> mistook the problem as requiring the ntp_lock changes
> that landed in 3.4 in order for it to occur.
>
> Unfortunately the same issue can happen (with only one cpu)
> as follows:
> do_adjtimex()
> write_seqlock_irq(&xtime_lock);
> process_adjtimex_modes()
> process_adj_status()
> ntp_start_leap_timer()
> hrtimer_start()
> hrtimer_reprogram()
> tick_program_event()
> clockevents_program_event()
> ktime_get()
> seq = req_seqbegin(xtime_lock); [DEADLOCK]
>
> This deadlock will no always occur, as it requires the
> leap_timer to force a hrtimer_reprogram which only happens
> if its set and there's no sooner timer to expire.
[...]
I remember this came through the leapsecond deadlock & hrtimer/futex
issue fixes. But I noted now commit 6b1859dba01c7d512b72d77e3fd7da8354235189
("ntp: Fix STA_INS/DEL clearing bug") was not included, and its changelog
says it fixes a problem introduced with this. Wouldn't it be worth/right to
also include it in 2.6.34? I didn't test etc., just detected through the
changelog/description but would expect it would be affected too. I also
noted it is missing from 3.2.y and 2.6.32.y stables, and perhaps should be
scheduled for inclusion in their cases too.
--
[]'s
Herton
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