freebsd-dev/sys/cddl
Allan Jude c79b58ccc5 Pull in a follow-on commit to resolve a deadlock in ZFS sequential
resilver (r334844)

MFV/ZoL: Fix deadlock in IO pipeline

commit a76f3d0437
Author: Brian Behlendorf <behlendorf1@llnl.gov>
Date:   Fri Mar 16 16:46:06 2018 -0700

    Fix deadlock in IO pipeline

    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()
            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>

Reported by:	ZFS Leadership Meeting
Reviewed by:	mav
Approved by:	re (kib)
Obtained from:	ZFS-on-Linux
MFC after:	2 weeks
Sponsored by:	Klara Systems
Differential Revision:	https://reviews.freebsd.org/D17495
2018-10-10 22:59:15 +00:00
..
boot/zfs Mark two things as unused (since they are only sometimes used) and 2017-12-03 04:55:33 +00:00
compat/opensolaris MFV/ZoL: add dbuf stats 2018-08-12 01:10:18 +00:00
contrib/opensolaris Pull in a follow-on commit to resolve a deadlock in ZFS sequential 2018-10-10 22:59:15 +00:00
dev Add support for 'C'-compressed ISA extension to DTrace FBT provider. 2018-09-03 14:34:09 +00:00