The patch titled
make cancel_xxx_work_sync() return a boolean
has been added to the -mm tree. Its filename is
make-cancel_xxx_work_sync-return-a-boolean.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: make cancel_xxx_work_sync() return a boolean
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Change cancel_work_sync() and cancel_delayed_work_sync() to return a boolean
indicating whether the work was actually cancelled. A zero return value means
that the work was not pending/queued.
Without that kind of change it is not possible to avoid flush_workqueue()
sometimes, see the next patch as an example.
Also, this patch unifies both functions and kills the (unlikely) busy-wait
loop.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Jarek Poplawski <jarkao2@xxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/workqueue.h | 4 +--
kernel/workqueue.c | 41 +++++++++++++++++++++++-------------
2 files changed, 29 insertions(+), 16 deletions(-)
diff -puN include/linux/workqueue.h~make-cancel_xxx_work_sync-return-a-boolean include/linux/workqueue.h
--- a/include/linux/workqueue.h~make-cancel_xxx_work_sync-return-a-boolean
+++ a/include/linux/workqueue.h
@@ -148,7 +148,7 @@ extern int keventd_up(void);
extern void init_workqueues(void);
int execute_in_process_context(work_func_t fn, struct execute_work *);
-extern void cancel_work_sync(struct work_struct *work);
+extern int cancel_work_sync(struct work_struct *work);
/*
* Kill off a pending schedule_delayed_work(). Note that the work callback
@@ -166,7 +166,7 @@ static inline int cancel_delayed_work(st
return ret;
}
-extern void cancel_delayed_work_sync(struct delayed_work *work);
+extern int cancel_delayed_work_sync(struct delayed_work *work);
/* Obsolete. use cancel_delayed_work_sync() */
static inline
diff -puN kernel/workqueue.c~make-cancel_xxx_work_sync-return-a-boolean kernel/workqueue.c
--- a/kernel/workqueue.c~make-cancel_xxx_work_sync-return-a-boolean
+++ a/kernel/workqueue.c
@@ -382,16 +382,16 @@ void fastcall flush_workqueue(struct wor
EXPORT_SYMBOL_GPL(flush_workqueue);
/*
- * Upon a successful return, the caller "owns" WORK_STRUCT_PENDING bit,
+ * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
* so this work can't be re-armed in any way.
*/
static int try_to_grab_pending(struct work_struct *work)
{
struct cpu_workqueue_struct *cwq;
- int ret = 0;
+ int ret = -1;
if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
- return 1;
+ return 0;
/*
* The queueing is in progress, or it is already queued. Try to
@@ -457,10 +457,28 @@ static void wait_on_work(struct work_str
wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
}
+static int __cancel_work_timer(struct work_struct *work,
+ struct timer_list* timer)
+{
+ int ret;
+
+ do {
+ ret = (timer && likely(del_timer(timer)));
+ if (!ret)
+ ret = try_to_grab_pending(work);
+ wait_on_work(work);
+ } while (unlikely(ret < 0));
+
+ work_clear_pending(work);
+ return ret;
+}
+
/**
* cancel_work_sync - block until a work_struct's callback has terminated
* @work: the work which is to be flushed
*
+ * Returns true if @work was pending.
+ *
* cancel_work_sync() will cancel the work if it is queued. If the work's
* callback appears to be running, cancel_work_sync() will block until it
* has completed.
@@ -476,12 +494,9 @@ static void wait_on_work(struct work_str
* The caller must ensure that workqueue_struct on which this work was last
* queued can't be destroyed before this function returns.
*/
-void cancel_work_sync(struct work_struct *work)
+int cancel_work_sync(struct work_struct *work)
{
- while (!try_to_grab_pending(work))
- cpu_relax();
- wait_on_work(work);
- work_clear_pending(work);
+ return __cancel_work_timer(work, NULL);
}
EXPORT_SYMBOL_GPL(cancel_work_sync);
@@ -489,16 +504,14 @@ EXPORT_SYMBOL_GPL(cancel_work_sync);
* cancel_delayed_work_sync - reliably kill off a delayed work.
* @dwork: the delayed work struct
*
+ * Returns true if @dwork was pending.
+ *
* It is possible to use this function if @dwork rearms itself via queue_work()
* or queue_delayed_work(). See also the comment for cancel_work_sync().
*/
-void cancel_delayed_work_sync(struct delayed_work *dwork)
+int cancel_delayed_work_sync(struct delayed_work *dwork)
{
- while (!del_timer(&dwork->timer) &&
- !try_to_grab_pending(&dwork->work))
- cpu_relax();
- wait_on_work(&dwork->work);
- work_clear_pending(&dwork->work);
+ return __cancel_work_timer(&dwork->work, &dwork->timer);
}
EXPORT_SYMBOL(cancel_delayed_work_sync);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
libata-core-convert-to-use-cancel_rearming_delayed_work.patch
freezer-make-kernel-threads-nonfreezable-by-default.patch
freezer-make-kernel-threads-nonfreezable-by-default-fix.patch
freezer-make-kernel-threads-nonfreezable-by-default-fix-fix.patch
freezer-make-kernel-threads-nonfreezable-by-default-fix-2.patch
freezer-run-show_state-when-freezing-times-out.patch
hibernation-prepare-to-enter-the-low-power-state.patch
freezer-avoid-freezing-kernel-threads-prematurely.patch
freezer-use-__set_current_state-in-refrigerator.patch
freezer-return-int-from-freeze_processes.patch
freezer-remove-redundant-check-in-try_to_freeze_tasks.patch
pm-prevent-frozen-user-mode-helpers-from-failing-the-freezing-of-tasks-rev-2.patch
add-generic-exit-time-stack-depth-checking-to-config_debug_stack_usage.patch
clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch
use-write_trylock_irqsave-in-ptrace_attach.patch
fix-stop_machine_run-problem-with-naughty-real-time-process.patch
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process.patch
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process-fix.patch
percpu_counters-use-cpu-notifiers.patch
percpu_counters-use-for_each_online_cpu.patch
mm-fix-create_new_namespaces-return-value.patch
adb_probe_task-remove-unneeded-flush_signals-call.patch
kcdrwd-remove-unneeded-flush_signals-call.patch
nbdcsock_xmit-cleanup-signal-related-code.patch
rename-cancel_rearming_delayed_work-to-cancel_delayed_work_sync.patch
make-cancel_xxx_work_sync-return-a-boolean.patch
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