The patch titled
workqueue: fix race condition in schedule_on_each_cpu()
has been added to the -mm tree. Its filename is
workqueue-fix-race-condition-in-schedule_on_each_cpu.patch
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------------------------------------------------------
Subject: workqueue: fix race condition in schedule_on_each_cpu()
From: Tejun Heo <tj@xxxxxxxxxx>
Commit 65a64464349883891e21e74af16c05d6e1eeb4e9 ("HWPOISON: Allow
schedule_on_each_cpu() from keventd") which allows schedule_on_each_cpu()
to be called from keventd added a race condition. schedule_on_each_cpu()
may race with cpu hotplug and end up executing the function twice on a
cpu.
Fix it by moving direct execution into the section protected with
get/put_online_cpus(). While at it, update code such that direct
execution is done after works have been scheduled for all other cpus and
drop unnecessary cpu != orig test from flush loop.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 28 +++++++++++++---------------
1 file changed, 13 insertions(+), 15 deletions(-)
diff -puN kernel/workqueue.c~workqueue-fix-race-condition-in-schedule_on_each_cpu kernel/workqueue.c
--- a/kernel/workqueue.c~workqueue-fix-race-condition-in-schedule_on_each_cpu
+++ a/kernel/workqueue.c
@@ -692,31 +692,29 @@ int schedule_on_each_cpu(work_func_t fun
if (!works)
return -ENOMEM;
+ get_online_cpus();
+
/*
- * when running in keventd don't schedule a work item on itself.
- * Can just call directly because the work queue is already bound.
- * This also is faster.
- * Make this a generic parameter for other workqueues?
+ * When running in keventd don't schedule a work item on
+ * itself. Can just call directly because the work queue is
+ * already bound. This also is faster.
*/
- if (current_is_keventd()) {
+ if (current_is_keventd())
orig = raw_smp_processor_id();
- INIT_WORK(per_cpu_ptr(works, orig), func);
- func(per_cpu_ptr(works, orig));
- }
- get_online_cpus();
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
- if (cpu == orig)
- continue;
INIT_WORK(work, func);
- schedule_work_on(cpu, work);
- }
- for_each_online_cpu(cpu) {
if (cpu != orig)
- flush_work(per_cpu_ptr(works, cpu));
+ schedule_work_on(cpu, work);
}
+ if (orig >= 0)
+ func(per_cpu_ptr(works, orig));
+
+ for_each_online_cpu(cpu)
+ flush_work(per_cpu_ptr(works, cpu));
+
put_online_cpus();
free_percpu(works);
return 0;
_
Patches currently in -mm which might be from tj@xxxxxxxxxx are
workqueue-fix-race-condition-in-schedule_on_each_cpu.patch
linux-next.patch
lib-vsprintfc-add-%pu-to-print-uuid-guids.patch
drivers-firmware-dmi_scanc-use-%pub-to-print-uuids.patch
efih-use-%pul-to-print-uuids.patch
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