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author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-04-29 10:00:29 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-29 17:06:11 +0200 |
commit | d2ba7e2ae206e9ab24e8937d99d0d5513bfd08e5 (patch) | |
tree | 4cdd43bbf03885705fed5c80e982d19d397afaeb /kernel/cpu.c | |
parent | cleanup_workqueue_thread: remove the unneeded "cpu" parameter (diff) | |
download | linux-d2ba7e2ae206e9ab24e8937d99d0d5513bfd08e5.tar.xz linux-d2ba7e2ae206e9ab24e8937d99d0d5513bfd08e5.zip |
simplify cpu_hotplug_begin()/put_online_cpus()
cpu_hotplug_begin() must be always called under cpu_add_remove_lock, this
means that only one process can be cpu_hotplug.active_writer. So we don't
need the cpu_hotplug.writer_queue, we can wake up the ->active_writer
directly.
Also, fix the comment.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Acked-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cpu.c')
-rw-r--r-- | kernel/cpu.c | 30 |
1 files changed, 10 insertions, 20 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index f8f9468d17d7..a98f6ab16ecd 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -33,17 +33,13 @@ static struct { * an ongoing cpu hotplug operation. */ int refcount; - wait_queue_head_t writer_queue; } cpu_hotplug; -#define writer_exists() (cpu_hotplug.active_writer != NULL) - void __init cpu_hotplug_init(void) { cpu_hotplug.active_writer = NULL; mutex_init(&cpu_hotplug.lock); cpu_hotplug.refcount = 0; - init_waitqueue_head(&cpu_hotplug.writer_queue); } #ifdef CONFIG_HOTPLUG_CPU @@ -65,11 +61,8 @@ void put_online_cpus(void) if (cpu_hotplug.active_writer == current) return; mutex_lock(&cpu_hotplug.lock); - cpu_hotplug.refcount--; - - if (unlikely(writer_exists()) && !cpu_hotplug.refcount) - wake_up(&cpu_hotplug.writer_queue); - + if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer)) + wake_up_process(cpu_hotplug.active_writer); mutex_unlock(&cpu_hotplug.lock); } @@ -98,8 +91,8 @@ void cpu_maps_update_done(void) * Note that during a cpu-hotplug operation, the new readers, if any, * will be blocked by the cpu_hotplug.lock * - * Since cpu_maps_update_begin is always called after invoking - * cpu_maps_update_begin, we can be sure that only one writer is active. + * Since cpu_hotplug_begin() is always called after invoking + * cpu_maps_update_begin(), we can be sure that only one writer is active. * * Note that theoretically, there is a possibility of a livelock: * - Refcount goes to zero, last reader wakes up the sleeping @@ -115,19 +108,16 @@ void cpu_maps_update_done(void) */ static void cpu_hotplug_begin(void) { - DECLARE_WAITQUEUE(wait, current); - - mutex_lock(&cpu_hotplug.lock); - cpu_hotplug.active_writer = current; - add_wait_queue_exclusive(&cpu_hotplug.writer_queue, &wait); - while (cpu_hotplug.refcount) { - set_current_state(TASK_UNINTERRUPTIBLE); + + for (;;) { + mutex_lock(&cpu_hotplug.lock); + if (likely(!cpu_hotplug.refcount)) + break; + __set_current_state(TASK_UNINTERRUPTIBLE); mutex_unlock(&cpu_hotplug.lock); schedule(); - mutex_lock(&cpu_hotplug.lock); } - remove_wait_queue_locked(&cpu_hotplug.writer_queue, &wait); } static void cpu_hotplug_done(void) |