workqueue_cpu_down_callback() is only used when HOTPLUG_CPU=y.
so it will be better if we use hotcpu_notifier() to register it.
When HOTPLUG_CPU=y, hotcpu_notifier() and cpu_notifier() are the same.
When HOTPLUG_CPU=n, if we use cpu_notifier(), workqueue_cpu_down_callback()
will be called(no-op) when booting and the memory of
workqueue_cpu_down_callback()
and gcwq_unbind_fn() will be discard after boot.
But if we use hotcpu_notifier(), we can avoid the no-op calls of
workqueue_cpu_down_callback(). And the memory of workqueue_cpu_down_callback()
and gcwq_unbind_fn() will be discard at build time:
$ ls -l kernel/workqueue.o.cpu_notifier kernel/workqueue.o.hotcpu_notifier
-rw-rw-r-- 1 laijs laijs 484080 Sep 15 11:31 kernel/workqueue.o.cpu_notifier
-rw-rw-r-- 1 laijs laijs 478240 Sep 15 11:31 kernel/workqueue.o.hotcpu_notifier
$ size kernel/workqueue.o.cpu_notifier kernel/workqueue.o.hotcpu_notifier
text data bss dec hex filename
18513 2387 1221 22121 5669 kernel/workqueue.o.cpu_notifier
18082 2355 1221 21658 549a kernel/workqueue.o.hotcpu_notifier
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
kernel/workqueue.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e8d3c95..fc4208a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3791,7 +3791,7 @@ static int __init init_workqueues(void)
WORK_CPU_LAST);
cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
- cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
+ hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
/* initialize gcwqs */
for_each_gcwq_cpu(cpu) {
--
1.7.4.4
--
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