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. Changes from the first take[L] are, * All updated patches rolled into the series and Acked-by's added.a * Tomi Valkeinen pointed out that mod_delayed_work() can't be called from IRQ handlers and thus can't replace __cancel_delayed_work() users. __cancel_delayed_work() users dropped from conversion. This will be handled by a future patchset. * Ensuring preemtion is disabled across PENDING manipulation doesn't make try_to_grab_pending() safe to use from bh context and making it impossible to replace even cancel_delayed_work() users. Whole patch series updated so that IRQ is disabled across PENDING manipulation instead. As most operations had to grab gcwq->lock anyway, this doesn't add extra IRQ toggling. * try_to_grab_pending() and __cancel_work_timer() updated to take bool @is_dwork instead of @timer and disable IRQ on successful return. This patchset contains the following fourteen patches. 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-irq-while-manipulating-PENDING.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 0001-0003 are preparatory. 0004 removes the possibility of cancel_sync spinning for extended period of time while another task holding PENDING is preempted or interrupted. 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 improved try_to_grab_pending() to implement mod_delayed_work[_on](). 0014 converts cancel + queue sequences to mod_delayed_work(). 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 ~130 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/genhd.c | 6 drivers/edac/edac_mc.c | 17 drivers/infiniband/core/addr.c | 4 drivers/infiniband/hw/nes/nes_hw.c | 6 drivers/infiniband/hw/nes/nes_nic.c | 5 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 fs/afs/callback.c | 4 fs/afs/server.c | 10 fs/afs/vlocation.c | 14 fs/nfs/nfs4renewd.c | 3 include/linux/workqueue.h | 47 +- kernel/workqueue.c | 732 ++++++++++++++++++++------------- net/core/dst.c | 4 net/rfkill/input.c | 3 20 files changed, 526 insertions(+), 399 deletions(-) -- tejun [1] http://thread.gmane.org/gmane.linux.kernel/1159922 [L] http://thread.gmane.org/gmane.linux.kernel/1334546 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/