Messages in this thread |  | | Date | Fri, 28 Feb 2014 12:34:27 -0500 | From | Prarit Bhargava <> | Subject | Re: smp_call_function_single with wait=0 considered harmful |
| |
On 02/28/2014 07:39 AM, Peter Zijlstra wrote: > On Fri, Feb 28, 2014 at 01:26:24PM +0100, Peter Zijlstra wrote: >> On Wed, Dec 04, 2013 at 08:46:27AM -0800, Christoph Hellwig wrote: >>> kernel/stop_machine.c:stop_two_cpus() >> >> That site should work with .wait=1 just fine, but given the above, the >> .wait=0 doesn't appear problematic at all. > > Scratch that; its broken, but not because of smp_call_function_single(). > > --- > Subject: stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus() > > We must use smp_call_function_single(.wait=1) for the > irq_cpu_stop_queue_work() to ensure the queueing is actually done under > stop_cpus_lock. Without this we could have dropped the lock by the time > we do the queueing and get the race we tried to fix. > > Fixes: 7053ea1a34fa ("stop_machine: Fix race between stop_two_cpus() and stop_cpus()") > Cc: Prarit Bhargava <prarit@redhat.com> > Cc: Rik van Riel <riel@redhat.com> > Cc: Mel Gorman <mgorman@suse.de> > Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
P.
|  |