HWPOISON: Allow schedule_on_each_cpu() from keventd

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>

1 files changed, 19 insertions, 2 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index addfe2df93b1..f61a2fecf281 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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;