[PATCH] Fix hardcoded cpu=0 in workqueue for per_cpu_ptr() calls

Tracked this down on an Ultra Enterprise 3000.  It's a 6-way machine.  Odd
thing about this machine (and it's good for finding bugs like this) is that
the CPU id's are not 0 based.  For instance, on my machine the CPU's are
6/7/10/11/14/15.

This caused some NULL pointer dereference in kernel/workqueue.c because for
single_threaded workqueue's, it hardcoded the cpu to 0.

I changed the 0's to any_online_cpu(cpu_online_mask), which cpumask.h
claims is "First cpu in mask".  So this fits the same usage.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 42df83d7fad2..2bd5aee1c736 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -102,7 +102,7 @@ int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 
         if (!test_and_set_bit(0, &work->pending)) {
                 if (unlikely(is_single_threaded(wq)))
-                        cpu = 0;
+                        cpu = any_online_cpu(cpu_online_map);
                 BUG_ON(!list_empty(&work->entry));
                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
                 ret = 1;
@@ -118,7 +118,7 @@ static void delayed_work_timer_fn(unsigned long __data)
         int cpu = smp_processor_id();
 
         if (unlikely(is_single_threaded(wq)))
-                cpu = 0;
+                cpu = any_online_cpu(cpu_online_map);
 
         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 }
@@ -266,8 +266,8 @@ void fastcall flush_workqueue(struct workqueue_struct *wq)
         might_sleep();
 
         if (is_single_threaded(wq)) {
-                /* Always use cpu 0's area. */
-                flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, 0));
+                /* Always use first cpu's area. */
+                flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, any_online_cpu(cpu_online_map)));
         } else {
                 int cpu;
 
@@ -320,7 +320,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
         lock_cpu_hotplug();
         if (singlethread) {
                 INIT_LIST_HEAD(&wq->list);
-                p = create_workqueue_thread(wq, 0);
+                p = create_workqueue_thread(wq, any_online_cpu(cpu_online_map));
                 if (!p)
                         destroy = 1;
                 else
@@ -374,7 +374,7 @@ void destroy_workqueue(struct workqueue_struct *wq)
         /* We don't need the distraction of CPUs appearing and vanishing. */
         lock_cpu_hotplug();
         if (is_single_threaded(wq))
-                cleanup_workqueue_thread(wq, 0);
+                cleanup_workqueue_thread(wq, any_online_cpu(cpu_online_map));
         else {
                 for_each_online_cpu(cpu)
                         cleanup_workqueue_thread(wq, cpu);