Fix deadlock in IO pipeline #7307
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tcaputi
approved these changes
Mar 16, 2018
Codecov Report
@@ Coverage Diff @@
## master #7307 +/- ##
==========================================
- Coverage 76.62% 76.39% -0.23%
==========================================
Files 328 328
Lines 104034 104039 +5
==========================================
- Hits 79716 79481 -235
- Misses 24318 24558 +240
Continue to review full report at Codecov.
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In vdev_queue_aggregate() the zio_execute() bypass should not be
called under the vdev queue lock. This can result in a deadlock
as shown in the stack traces below.
Drop the vdev queue lock then walk the parents of the aggregate IO
to determine the list of component IOs to be bypassed. This can
be done safely without holding the io_lock since the new aggregate
IO has not yet been returned and its parents cannot change.
--- THREAD 1 ---
arc_read()
zio_nowait()
zio_vdev_io_start()
vdev_queue_io() <--- mutex_enter(vq->vq_lock)
vdev_queue_io_to_issue()
vdev_queue_aggregate()
zio_execute()
zio_vdev_io_assess()
zio_wait_for_children() <- mutex_enter(zio->io_lock)
--- THREAD 2 --- (inverse order)
arc_read()
zio_change_priority() <- mutex_enter(zio->zio_lock)
vdev_queue_change_io_priority() <- mutex_enter(vq->vq_lock)
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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Refreshed to address the feedback and I've removed the WIP label. |
don-brady
approved these changes
Mar 16, 2018
dweeezil
pushed a commit
to dweeezil/zfs
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Apr 10, 2018
In vdev_queue_aggregate() the zio_execute() bypass should not be
called under the vdev queue lock. This can result in a deadlock
as shown in the stack traces below.
Drop the vdev queue lock then walk the parents of the aggregate IO
to determine the list of component IOs to be bypassed. This can
be done safely without holding the io_lock since the new aggregate
IO has not yet been returned and its parents cannot change.
--- THREAD 1 ---
arc_read()
zio_nowait()
zio_vdev_io_start()
vdev_queue_io() <--- mutex_enter(vq->vq_lock)
vdev_queue_io_to_issue()
vdev_queue_aggregate()
zio_execute()
zio_vdev_io_assess()
zio_wait_for_children() <- mutex_enter(zio->io_lock)
--- THREAD 2 --- (inverse order)
arc_read()
zio_change_priority() <- mutex_enter(zio->zio_lock)
vdev_queue_change_io_priority() <- mutex_enter(vq->vq_lock)
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Don Brady <don.brady@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#7307
dweeezil
pushed a commit
to dweeezil/zfs
that referenced
this pull request
Apr 10, 2018
In vdev_queue_aggregate() the zio_execute() bypass should not be
called under the vdev queue lock. This can result in a deadlock
as shown in the stack traces below.
Drop the vdev queue lock then walk the parents of the aggregate IO
to determine the list of component IOs to be bypassed. This can
be done safely without holding the io_lock since the new aggregate
IO has not yet been returned and its parents cannot change.
--- THREAD 1 ---
arc_read()
zio_nowait()
zio_vdev_io_start()
vdev_queue_io() <--- mutex_enter(vq->vq_lock)
vdev_queue_io_to_issue()
vdev_queue_aggregate()
zio_execute()
zio_vdev_io_assess()
zio_wait_for_children() <- mutex_enter(zio->io_lock)
--- THREAD 2 --- (inverse order)
arc_read()
zio_change_priority() <- mutex_enter(zio->zio_lock)
vdev_queue_change_io_priority() <- mutex_enter(vq->vq_lock)
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Don Brady <don.brady@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#7307
dweeezil
pushed a commit
to dweeezil/zfs
that referenced
this pull request
Apr 10, 2018
In vdev_queue_aggregate() the zio_execute() bypass should not be
called under the vdev queue lock. This can result in a deadlock
as shown in the stack traces below.
Drop the vdev queue lock then walk the parents of the aggregate IO
to determine the list of component IOs to be bypassed. This can
be done safely without holding the io_lock since the new aggregate
IO has not yet been returned and its parents cannot change.
--- THREAD 1 ---
arc_read()
zio_nowait()
zio_vdev_io_start()
vdev_queue_io() <--- mutex_enter(vq->vq_lock)
vdev_queue_io_to_issue()
vdev_queue_aggregate()
zio_execute()
zio_vdev_io_assess()
zio_wait_for_children() <- mutex_enter(zio->io_lock)
--- THREAD 2 --- (inverse order)
arc_read()
zio_change_priority() <- mutex_enter(zio->zio_lock)
vdev_queue_change_io_priority() <- mutex_enter(vq->vq_lock)
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Don Brady <don.brady@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#7307
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Description
Replaces #7301.
In
vdev_queue_aggregate()thezio_execute()bypass should not be called under the vdev queue lock. This can result in a deadlock as shown in the stack traces below.Drop the vdev queue lock then walk the parents of the aggregate IO to determine the list of component IOs to be bypassed. This can be done safely without holding the io_lock since the new aggregate IO has not yet been returned and its parents cannot change.
Motivation and Context
Any deadlock like this in the pipeline could manifest itself as a hang. It may explain issues like #7241 and #7059 which have been observed in master. This specific issue was introduced in a8b2e30 (zfs-0.7.0-223-ga8b2e30) and does not impact the 0.7 release branch.
How Has This Been Tested?
The issue was reliably reproducible with the
sequential_readstest case from the perf-regression tests.Types of changes
Checklist:
Signed-off-by.