Skip to content

L
linux
Switch branch/tag
  1. 28 Jul, 2017 1 commit
    • Michael Bringmann's avatar
      workqueue: Work around edge cases for calc of pool's cpumask · 1ad0f0a7
      Michael Bringmann authored 
      There is an underlying assumption/trade-off in many layers of the Linux
system that CPU <-> node mapping is static.  This is despite the presence
of features like NUMA and 'hotplug' that support the dynamic addition/
removal of fundamental system resources like CPUs and memory.  PowerPC
systems, however, do provide extensive features for the dynamic change
of resources available to a system.

Currently, there is little or no synchronization protection around the
updating of the CPU <-> node mapping, and the export/update of this
information for other layers / modules.  In systems which can change
this mapping during 'hotplug', like PowerPC, the information is changing
underneath all layers that might reference it.

This patch attempts to ensure that a valid, usable cpumask attribute
is used by the workqueue infrastructure when setting up new resource
pools.  It prevents a crash that has been observed when an 'empty'
cpumask is passed along to the worker/task scheduling code.  It is
intended as a temporary workaround until a more fundamental review and
correction of the issue can be done.

[With additions to the patch provided by Tejun Hao <tj@kernel.org>]
Signed-off-by: default avatarMichael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      1ad0f0a7
  3. 25 Jul, 2017 1 commit
    • Tejun Heo's avatar
      workqueue: implicit ordered attribute should be overridable · 0a94efb5
      Tejun Heo authored 
      5c0338c6 ("workqueue: restore WQ_UNBOUND/max_active==1 to be
ordered") automatically enabled ordered attribute for unbound
workqueues w/ max_active == 1.  Because ordered workqueues reject
max_active and some attribute changes, this implicit ordered mode
broke cases where the user creates an unbound workqueue w/ max_active
== 1 and later explicitly changes the related attributes.

This patch distinguishes explicit and implicit ordered setting and
overrides from attribute changes if implict.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Fixes: 5c0338c6 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
      0a94efb5
  5. 19 Jul, 2017 1 commit
    • Tejun Heo's avatar
      workqueue: restore WQ_UNBOUND/max_active==1 to be ordered · 5c0338c6
      Tejun Heo authored 
      The combination of WQ_UNBOUND and max_active == 1 used to imply
ordered execution.  After NUMA affinity 4c16bd32 ("workqueue:
implement NUMA affinity for unbound workqueues"), this is no longer
true due to per-node worker pools.

While the right way to create an ordered workqueue is
alloc_ordered_workqueue(), the documentation has been misleading for a
long time and people do use WQ_UNBOUND and max_active == 1 for ordered
workqueues which can lead to subtle bugs which are very difficult to
trigger.

It's unlikely that we'd see noticeable performance impact by enforcing
ordering on WQ_UNBOUND / max_active == 1 workqueues.  Let's
automatically set __WQ_ORDERED for those workqueues.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarChristoph Hellwig <hch@infradead.org>
Reported-by: default avatarAlexei Potashnik <alexei@purestorage.com>
Fixes: 4c16bd32 ("workqueue: implement NUMA affinity for unbound workqueues")
Cc: stable@vger.kernel.org # v3.10+
      5c0338c6
  7. 18 Jul, 2017 22 commits
  9. 17 Jul, 2017 15 commits
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7