The patch titled
workqueues: shrink cpu_populated_map when CPU dies
has been added to the -mm tree. Its filename is
workqueues-shrink-cpu_populated_map-when-cpu-dies.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: workqueues: shrink cpu_populated_map when CPU dies
From: Oleg Nesterov <oleg@xxxxxxxxxx>
When cpu_populated_map was introduced, it was supposed that cwq->thread can
survive after CPU_DEAD, that is why we never shrink cpu_populated_map.
This is not very nice, we can safely remove the already dead CPU from the map.
The only required change is that destroy_workqueue() must hold the hotplug
lock until it destroys all cwq->thread's, to protect the cpu_populated_map.
We could make the local copy of cpu mask and drop the lock, but
sizeof(cpumask_t) may be very large.
Also, fix the comment near queue_work(). Unless _cpu_down() happens we do
guarantee the cpu-affinity of the work_struct, and we have users which rely on
this.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff -puN kernel/workqueue.c~workqueues-shrink-cpu_populated_map-when-cpu-dies kernel/workqueue.c
--- a/kernel/workqueue.c~workqueues-shrink-cpu_populated_map-when-cpu-dies
+++ a/kernel/workqueue.c
@@ -158,8 +158,8 @@ static void __queue_work(struct cpu_work
*
* Returns 0 if @work was already on a queue, non-zero otherwise.
*
- * We queue the work to the CPU it was submitted, but there is no
- * guarantee that it will be processed by that CPU.
+ * We queue the work to the CPU it was submitted, but if CPU dies
+ * it can be processed by another CPU.
*/
int queue_work(struct workqueue_struct *wq, struct work_struct *work)
{
@@ -813,12 +813,12 @@ void destroy_workqueue(struct workqueue_
spin_lock(&workqueue_lock);
list_del(&wq->list);
spin_unlock(&workqueue_lock);
- put_online_cpus();
for_each_cpu_mask(cpu, *cpu_map) {
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
cleanup_workqueue_thread(cwq, cpu);
}
+ put_online_cpus();
free_percpu(wq->cpu_wq);
kfree(wq);
@@ -836,7 +836,6 @@ static int __devinit workqueue_cpu_callb
action &= ~CPU_TASKS_FROZEN;
switch (action) {
-
case CPU_UP_PREPARE:
cpu_set(cpu, cpu_populated_map);
}
@@ -864,6 +863,12 @@ static int __devinit workqueue_cpu_callb
}
}
+ switch (action) {
+ case CPU_UP_CANCELED:
+ case CPU_DEAD:
+ cpu_clear(cpu, cpu_populated_map);
+ }
+
return NOTIFY_OK;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
mmap_region-cleanup-the-final-vma_merge-related-code.patch
remove-unused-variable-from-send_signal.patch
turn-legacy_queue-macro-into-static-inline-function.patch
consolidate-checking-for-ignored-legacy-signals.patch
consolidate-checking-for-ignored-legacy-signals-simplify.patch
signals-do_signal_stop-use-signal_group_exit.patch
signals-do_group_exit-use-signal_group_exit-more-consistently.patch
workqueues-shrink-cpu_populated_map-when-cpu-dies.patch
workqueues-shrink-cpu_populated_map-when-cpu-dies-fix.patch
cleanup_workqueue_thread-remove-the-unneeded-cpu-parameter.patch
simplify-cpu_hotplug_begin-put_online_cpus.patch
timers-simplify-lockdep-stuff.patch
hrtimers-simplify-lockdep-stuff.patch
kill-double_spin_lock.patch
procfs-task-exe-symlink.patch
procfs-task-exe-symlink-fix.patch
free_pidmap-turn-it-into-free_pidmapstruct-upid.patch
-
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