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* [RFC][PATCH 0/2] hrtimer breakage
@ 2008-01-28 10:39 Peter Zijlstra
  2008-01-28 10:39 ` [RFC][PATCH 1/2] Fix many ARM timer handlers Peter Zijlstra
  2008-01-28 10:39 ` [RFC][PATCH 2/2] xtime_lock vs update_process_times Peter Zijlstra
  0 siblings, 2 replies; 8+ messages in thread
From: Peter Zijlstra @ 2008-01-28 10:39 UTC (permalink / raw)
  To: rth, rmk, bryan.wu, dhowells, gerg, lethal, wli, davem
  Cc: linux-kernel, linux-arch, tglx, mingo, torvalds, a.p.zijlstra

Hi,

If you're in the To: field, I broke your arch with (post .24) commit:
  d3d74453c34f8fd87674a8cf5b8a327c68f22e99

So, to be clear, that broke:
  alpha, arm, blackfin, frv, m68knommu, sh, sh64 and sparc

The deadlock resulting was found by Russell:

  IRQ handle 
    -> timer_tick() - xtime seqlock held for write
      -> update_process_times() 
        -> run_local_timers()
          -> hrtimer_run_queues()
            -> hrtimer_get_softirq_time() - tries to get a read lock

Now, Thomas assures me the fix is trivial, only do_timer() needs to be
done under the xtime_lock, and update_process_times() can savely be removed
from under it.

So that is what the next two patches do, the first patch is by Russell and
covers most of the arm sub-arch, the second one does the other archs and a
few arm archs that were missed by rmk.

This patch should probably be folded into one, or at least the arm bits
from the second moved to the first patch, to avoid more bisect breakage.

If you're all ok I'll polish the patches (maybe one per arch?) and ask for
merger.

(for obvious reasons I'm unable to actually test any of this)

Peter


^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2008-02-13 21:48 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2008-01-28 10:39 [RFC][PATCH 0/2] hrtimer breakage Peter Zijlstra
2008-01-28 10:39 ` [RFC][PATCH 1/2] Fix many ARM timer handlers Peter Zijlstra
2008-01-28 10:39 ` [RFC][PATCH 2/2] xtime_lock vs update_process_times Peter Zijlstra
2008-01-28 12:20   ` Russell King
2008-01-28 12:29     ` Peter Zijlstra
2008-01-28 13:40     ` Russell King
2008-02-04  1:29   ` Greg Ungerer
2008-02-13 21:18   ` Ivan Kokshaysky

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