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SubjectRe: [PATCH] cpu hotplug fix
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On Sun, 2004-03-21 at 10:12, Andrew Morton wrote:
> Rusty Russell <rusty@rustcorp.com.au> wrote:
> >
> > Name: Remove Strange start_cpu_timer Code
> > Status: Untested
> oy.
>
> Program received signal SIGTRAP, Trace/breakpoint trap.

Yep. This one is better, and actually tested.

Name: Remove Strange start_cpu_timer Code
Status: Tested on 2.6.5-rc2-bk1

start_cpu_timer is called once for every online CPU, then again in the
cpu up callback, hence the rt->function re-entrance check. Just call
it manually for the boot cpu, and use the notifier for the others.

Perhaps at one stage this code was run before timers were available:
this is no longer true (timers are initialized as part of scheduler
startup).

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.5-rc2-bk1/mm/slab.c working-2.6.5-rc2-bk1-start_cpu_timer-cleanup/mm/slab.c
--- linux-2.6.5-rc2-bk1/mm/slab.c 2004-03-20 21:21:33.000000000 +1100
+++ working-2.6.5-rc2-bk1-start_cpu_timer-cleanup/mm/slab.c 2004-03-22 14:41:07.000000000 +1100
@@ -576,13 +576,11 @@ static void __slab_error(const char *fun
{
struct timer_list *rt = &per_cpu(reap_timers, cpu);

- if (rt->function == NULL) {
- init_timer(rt);
- rt->expires = jiffies + HZ + 3*cpu;
- rt->data = cpu;
- rt->function = reap_timer_fnc;
- add_timer_on(rt, cpu);
- }
+ init_timer(rt);
+ rt->data = cpu;
+ rt->function = reap_timer_fnc;
+ rt->expires = jiffies + HZ + 3*cpu;
+ add_timer_on(rt, cpu);
}

#ifdef CONFIG_HOTPLUG_CPU
@@ -594,11 +592,8 @@ static void stop_cpu_timer(int cpu)
{
struct timer_list *rt = &per_cpu(reap_timers, cpu);

- if (rt->function) {
- del_timer_sync(rt);
- WARN_ON(timer_pending(rt));
- rt->function = NULL;
- }
+ del_timer_sync(rt);
+ WARN_ON(timer_pending(rt));
}
#endif

@@ -779,35 +774,14 @@ void __init kmem_cache_init(void)
/* Done! */
g_cpucache_up = FULL;

+ start_cpu_timer(smp_processor_id());
+
/* Register a cpu startup notifier callback
* that initializes ac_data for all new cpus
*/
register_cpu_notifier(&cpucache_notifier);
-
-
- /* The reap timers are started later, with a module init call:
- * That part of the kernel is not yet operational.
- */
}

-int __init cpucache_init(void)
-{
- int cpu;
-
- /*
- * Register the timers that return unneeded
- * pages to gfp.
- */
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
- if (cpu_online(cpu))
- start_cpu_timer(cpu);
- }
-
- return 0;
-}
-
-__initcall(cpucache_init);
-
/*
* Interface to system's page allocator. No need to hold the cache-lock.
*

--
Anyone who quotes me in their signature is an idiot -- Rusty Russell

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