Commit a0d8cdb6 authored Oct 18, 2007 by Akinobu Mita Committed by Linus Torvalds Oct 18, 2007

cpu hotplug: cpu: deliver CPU_UP_CANCELED only to NOTIFY_OKed callbacks with CPU_UP_PREPARE



The functions in a CPU notifier chain is called with CPU_UP_PREPARE event
before making the CPU online.  If one of the callback returns NOTIFY_BAD, it
stops to deliver CPU_UP_PREPARE event, and CPU online operation is canceled.
Then CPU_UP_CANCELED event is delivered to the functions in a CPU notifier
chain again.

This CPU_UP_CANCELED event is delivered to the functions which have been
called with CPU_UP_PREPARE, not delivered to the functions which haven't been
called with CPU_UP_PREPARE.

The problem that makes existing cpu hotplug error handlings complex is that
the CPU_UP_CANCELED event is delivered to the function that has returned
NOTIFY_BAD, too.

Usually we don't expect to call destructor function against the object that
has failed to initialize.  It is like:

	err = register_something();
	if (err) {
		unregister_something();
		return err;
	}

So it is natural to deliver CPU_UP_CANCELED event only to the functions that
have returned NOTIFY_OK with CPU_UP_PREPARE event and not to call the function
that have returned NOTIFY_BAD.  This is what this patch is doing.

Otherwise, every cpu hotplug notifiler has to track whether notifiler event is
failed or not for each cpu.  (drivers/base/topology.c is doing this with
topology_dev_map)

Similary this patch makes same thing with CPU_DOWN_PREPARE and CPU_DOWN_FAILED
evnets.

Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 12d00f6a

kernel/cpu.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -150,6 +150,7 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
		err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE \| mod,
		hcpu, -1, &nr_calls);
		if (err == NOTIFY_BAD) {
		nr_calls--;
		__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED \| mod,
		hcpu, nr_calls, NULL);
		printk("%s: attempt to take down CPU %u failed\n",
		@@ -233,6 +234,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
		ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE \| mod, hcpu,
		-1, &nr_calls);
		if (ret == NOTIFY_BAD) {
		nr_calls--;
		printk("%s: attempt to bring up CPU %u failed\n",
		__FUNCTION__, cpu);
		ret = -EINVAL;

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