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Gmane
From: Tejun Heo <tj <at> kernel.org>
Subject: [PATCHSET wq/for-3.7] workqueue: implement mod_delayed_work[_on]()
Newsgroups: gmane.linux.kernel
Date: Friday 27th July 2012 23:54:53 UTC (over 4 years ago)
delayed_work has been annoyingly missing the mechanism to modify timer
of a pending delayed_work - ie. mod_timer() counterpart.  delayed_work
users have been working around this using several methods - using an
explicit timer + work item, messing directly with delayed_work->timer,
and canceling before re-queueing, all of which are error-prone and/or
ugly.

Gustavo Padovan posted a RFC implementation[1] of mod_delayed_work() a
while back but it wasn't complete.  To properly implement
mod_delayed_work[_on](), it should be able to steal pending work items
which may be on timer or worklist or anywhere inbetween.  This is
similar to what __cancel_work_timer() does but it turns out that there
are a lot of holes around this area and try_to_grab_pending() needs
considerable amount of work to be used for other purposes too.

This patchset improves canceling and try_to_grab_pending(), use it to
implement mod_delayed_work[_on](), convert easy ones, and drop
__cancel_delayed_work_sync() which doesn't have relevant users
afterwards.

 0001-workqueue-reorder-queueing-functions-so-that-_on-var.patch
 0002-workqueue-make-queueing-functions-return-bool.patch
 0003-workqueue-add-missing-smp_wmb-in-process_one_work.patch
 0004-workqueue-disable-preemption-while-manipulating-PEND.patch
 0005-workqueue-set-delayed_work-timer-function-on-initial.patch
 0006-workqueue-unify-local-CPU-queueing-handling.patch
 0007-workqueue-fix-zero-delay-handling-of-queue_delayed_w.patch
 0008-workqueue-move-try_to_grab_pending-upwards.patch
 0009-workqueue-introduce-WORK_OFFQ_FLAG_.patch
 0010-workqueue-factor-out-__queue_delayed_work-from-queue.patch
 0011-workqueue-reorganize-try_to_grab_pending-and-__cance.patch
 0012-workqueue-mark-a-work-item-being-canceled-as-such.patch
 0013-workqueue-implement-mod_delayed_work-_on.patch
 0014-workqueue-use-mod_delayed_work-instead-of-cancel-que.patch
 0015-workqueue-deprecate-__cancel_delayed_work.patch

0001-0003 are preparatory.

0004 removes the possibility of cancel_sync spinning for extended
period of time while another task holding PENDING is preempted.

0005-0007 clean up local queueing handling.

0008-0011 prepare for try_to_grab_pending() improvements.

0012 makes try_to_grab_pending() distinguish transient failure which
can be safely busy-retried and failure because the work item is being
canceled, which may take arbitrary amount of time.

0013 uses the improve try_to_grab_pending() to implement
mod_delayed_work[_on]().

0014 converts cancel + queue sequences to mod_delayed_work().

0015 drops __cancel_delayed_work() which doesn't have any relevant
user left.  Not all conversions are trivial.  If you're involved with
edac, thinkpad_acpi, charger-manager, thermal_sys or nic link_watch,
please take a look at the conversion made in 0015.

This patchset is also available at the following git branch.

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git
review-wq-mod_delayed

If nobody objects, I'd like to route this series through wq/for-3.7.
Changes to other subsystems are fairly localized and conflicts, if
they occur, shouldn't be too painful to handle.

Although this ends up adding ~90 LOC, it contains a lot more
documentation, converted only the apparent ones, and IMHO is
worthwhile to have regardless as it removes an annoyance which is
pretty easy to encounter while using delayed_work.

Thanks.

 block/blk-core.c                       |    8 
 block/blk-throttle.c                   |    7 
 block/genhd.c                          |    6 
 drivers/block/floppy.c                 |    5 
 drivers/edac/edac_mc.c                 |   17 
 drivers/infiniband/core/addr.c         |    4 
 drivers/infiniband/core/mad.c          |   16 
 drivers/infiniband/hw/nes/nes_hw.c     |    6 
 drivers/infiniband/hw/nes/nes_nic.c    |    5 
 drivers/input/keyboard/qt2160.c        |    3 
 drivers/input/mouse/synaptics_i2c.c    |    7 
 drivers/net/wireless/ipw2x00/ipw2100.c |    8 
 drivers/net/wireless/zd1211rw/zd_usb.c |    3 
 drivers/platform/x86/thinkpad_acpi.c   |   20 
 drivers/power/charger-manager.c        |    9 
 drivers/power/ds2760_battery.c         |    9 
 drivers/power/jz4740-battery.c         |    6 
 drivers/thermal/thermal_sys.c          |   15 
 drivers/video/omap2/dss/dsi.c          |    2 
 fs/afs/callback.c                      |    4 
 fs/afs/server.c                        |   10 
 fs/afs/vlocation.c                     |   14 
 fs/nfs/nfs4renewd.c                    |    3 
 include/linux/workqueue.h              |   49 +-
 kernel/workqueue.c                     |  690
++++++++++++++++++++-------------
 net/core/dst.c                         |    4 
 net/core/link_watch.c                  |   21 -
 net/rfkill/input.c                     |    3 
 28 files changed, 521 insertions(+), 433 deletions(-)

--
tejun

[1] http://thread.gmane.org/gmane.linux.kernel/1159922
 
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