[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>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 42df83d..2bd5aee 100644 (file)
--- 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);