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  1. 10 May, 2011 36 commits
  3. 09 May, 2011 4 commits
    • Linus Torvalds's avatar
      Merge branch 'drm-intel-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/keithp/linux-2.6 · c191f6cc
      Linus Torvalds authored 
      * 'drm-intel-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/keithp/linux-2.6:
  drm/i915/lvds: Only act on lid notify when the device is on
  drm/i915: fix intel_crtc_clock_get pipe reads after "cleanup cleanup"
  drm/i915: Only enable the plane after setting the fb base (pre-ILK)
  drm/i915/dp: Be paranoid in case we disable a DP before it is attached
  drm/i915: Release object along create user fb error path
      c191f6cc
    • Dave Chinner's avatar
      xfs: fix race condition in AIL push trigger · 7ac95657
      Dave Chinner authored 
      The recent conversion of the xfsaild functionality to a work queue
introduced a hard-to-hit log space grant hang. One is caused by a
race condition in determining whether there is a psh in progress or
not.

The XFS_AIL_PUSHING_BIT is used to determine whether a push is
currently in progress.  When the AIL push work completes, it checked
whether the target changed and cleared the PUSHING bit to allow a
new push to be requeued. The race condition is as follows:

	Thread 1		push work

	smp_wmb()
				smp_rmb()
				check ailp->xa_target unchanged
	update ailp->xa_target
	test/set PUSHING bit
	does not queue
				clear PUSHING bit
				does not requeue

Now that the push target is updated, new attempts to push the AIL
will not trigger as the push target will be the same, and hence
despite trying to push the AIL we won't ever wake it again.

The fix is to ensure that the AIL push work clears the PUSHING bit
before it checks if the target is unchanged.

As a result, both push triggers operate on the same test/set bit
criteria, so even if we race in the push work and miss the target
update, the thread requesting the push will still set the PUSHING
bit and queue the push work to occur. For safety sake, the same
queue check is done if the push work detects the target change,
though only one of the two will will queue new work due to the use
of test_and_set_bit() checks.
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarAlex Elder <aelder@sgi.com>

(cherry picked from commit e4d3c4a4)
      7ac95657
    • Dave Chinner's avatar
      xfs: make AIL target updates and compares 32bit safe. · fe0da767
      Dave Chinner authored 
      The recent conversion of the xfsaild functionality to a work queue
introduced a hard-to-hit log space grant hang. One of the problems
noticed was that updates of the push target are not 32 bit safe as
the target is a 64 bit value.

We cannot copy a 64 bit LSN without the possibility of corrupting
the result when racing with another updating thread. We have
function to do this update safely without needing to care about
32/64 bit issues - xfs_trans_ail_copy_lsn() - so use that when
updating the AIL push target.

Also move the reading of the target in the push work inside the AIL
lock, and use XFS_LSN_CMP() for the unlocked comparison during work
termination to close read holes as well.
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarAlex Elder <aelder@sgi.com>

(cherry picked from commit fd5670f2)
      fe0da767
    • Dave Chinner's avatar
      xfs: always push the AIL to the target · 50e86686
      Dave Chinner authored 
      The recent conversion of the xfsaild functionality to a work queue
introduced a hard-to-hit log space grant hang. One of the problems
discovered is a target mismatch between the item pushing loop and
the target itself.

The push trigger checks for the target increasing (i.e. new target >
current) while the push loop only pushes items that have a LSN <
current. As a result, we can get the situation where the push target
is X, the items at the tail of the AIL have LSN X and they don't get
pushed. The push work then completes thinking it is done, and cannot
be restarted until the push target increases to >= X + 1. If the
push target then never increases (because the tail is not moving),
then we never run the push work again and we stall.

Fix it by making sure log items with a LSN that matches the target
exactly are pushed during the loop.
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarAlex Elder <aelder@sgi.com>

(cherry picked from commit cb64026b)
      50e86686
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