Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 01/21] workqueue: fix race condition in schedule_on_each_cpu() | Date | Tue, 17 Nov 2009 02:15:06 +0900 |
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Commit 65a64464349883891e21e74af16c05d6e1eeb4e9 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@kernel.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: Oleg Nesterov <oleg@redhat.com> --- kernel/workqueue.c | 28 +++++++++++++--------------- 1 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 1232814..67e526b 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -692,31 +692,29 @@ int schedule_on_each_cpu(work_func_t func) 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; -- 1.6.4.2
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