Hotplug CPU: don't check cpu_online after take_cpu_down
Akinobu points out that if take_cpu_down() succeeds, the cpu must be offline.
Remove the cpu_online() check, and put a BUG_ON().
Quoting Akinobu Mita:
Actually the cpu_online() check was necessary before appling this
stop_machine: simplify patch.
With old __stop_machine_run(), __stop_machine_run() could succeed
(return !IS_ERR(p) value) even if take_cpu_down() returned non-zero value.
The return value of take_cpu_down() was obtained through kthread_stop()..
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Akinobu Mita" <akinobu.mita@gmail.com>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index cf79bb9..53cf508 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -250,8 +250,7 @@
set_cpus_allowed_ptr(current, &tmp);
err = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
-
- if (err || cpu_online(cpu)) {
+ if (err) {
/* CPU didn't die: tell everyone. Can't complain. */
if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
hcpu) == NOTIFY_BAD)
@@ -259,6 +258,7 @@
goto out_allowed;
}
+ BUG_ON(cpu_online(cpu));
/* Wait for it to sleep (leaving idle task). */
while (!idle_cpu(cpu))