Commit 04321587 authored Jul 28, 2008 by Rusty Russell

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>

parent ffdb5976

kernel/cpu.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -250,8 +250,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
		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 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)

		goto out_allowed;
		}
		BUG_ON(cpu_online(cpu));

		/* Wait for it to sleep (leaving idle task). */
		while (!idle_cpu(cpu))