Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning

KAMEZAWA Hiroyuki
2009-01-08T02:50:32Z

On Wed, 7 Jan 2009 21:33:31 -0500 (EST)
Steven Rostedt <rostedt@goodmis.org> wrote:

>
> On Wed, 7 Jan 2009, Linus Torvalds wrote:
> > > Should that be:
> > >
> > > #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_MEMORY_HOTPLUG)
> >
> > Well, probably CONFIG_MEMORY_HOTREMOVE, no? And I'd actually suggest that
> > unplugging should have a stop-machine if it doesn't already, just because
> > it's such a special case - like module removal.
>
> I do not think stop-machine will help, unless that spinning is protected
> by preempt-disable. If the task gets preempted after grabbing the owner
> thread_info, and then stop-machine runs, the memory disappears, the task
> is scheduled back, accesses the owner thread_info and then page-fault.
>
How about recording "cpu" into mutex at locking explicitly ?
too bad ?

-Kame