workqueue: restore POOL_MANAGING_WORKERS

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This patch restores POOL_MANAGING_WORKERS which was replaced by
pool->manager_mutex by 6037315269 "workqueue: use mutex for global_cwq
manager exclusion".

There's a subtle idle worker depletion bug across CPU hotplug events
and we need to distinguish an actual manager and CPU hotplug
preventing management.  POOL_MANAGING_WORKERS will be used for the
former and manager_mutex the later.

This patch just lays POOL_MANAGING_WORKERS on top of the existing
manager_mutex and doesn't introduce any synchronization changes.  The
next patch will update it.

Note that this patch fixes a non-critical anomaly where
too_many_workers() may return %true spuriously while CPU hotplug is in
progress.  While the issue could schedule idle timer spuriously, it
didn't trigger any actual misbehavior.

tj: Rewrote patch description.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

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This commit is contained in:

Lai Jiangshan 2012-09-10 10:03:33 -07:00 • committed by Tejun Heo

parent ec58815ab0

commit 552a37e936

1 changed files with 4 additions and 1 deletions

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kernel/workqueue.c

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