HWPOISON: Allow schedule_on_each_cpu() from keventd
Andi Kleen [Wed, 14 Oct 2009 04:22:47 +0000 (06:22 +0200)]
Right now when calling schedule_on_each_cpu() from keventd there
is a deadlock because it tries to schedule a work item on the current CPU
too. This happens via lru_add_drain_all() in hwpoison.

Just call the function for the current CPU in this case. This is actually
faster too.

Debugging with Fengguang Wu & Max Asbock

Signed-off-by: Andi Kleen <ak@linux.intel.com>

kernel/workqueue.c

index addfe2d..f61a2fe 100644 (file)
@@ -667,21 +667,38 @@ EXPORT_SYMBOL(schedule_delayed_work_on);
 int schedule_on_each_cpu(work_func_t func)
 {
        int cpu;
+       int orig = -1;
        struct work_struct *works;
 
        works = alloc_percpu(struct work_struct);
        if (!works)
                return -ENOMEM;
 
+       /*
+        * 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?
+        */
+       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)
-               flush_work(per_cpu_ptr(works, cpu));
+       for_each_online_cpu(cpu) {
+               if (cpu != orig)
+                       flush_work(per_cpu_ptr(works, cpu));
+       }
        put_online_cpus();
        free_percpu(works);
        return 0;