Re: sched: memory corruption on completing completions

[Raghavendra K T]

On 02/06/2015 12:18 PM, Raghavendra K T wrote:
> On 02/06/2015 04:27 AM, Linus Torvalds wrote:
> > On Thu, Feb 5, 2015 at 2:37 PM, Davidlohr Bueso <dave@xxxxxxxxxxxx>
> > wrote:
> > > > It is possible that the paravirt spinlocks could be saved by:
> > > >
> > > >   - moving the clearing of TICKET_SLOWPATH_FLAG into the fastpath
> > > > locking code.
> > >
> > > Ouch, to avoid deadlocks they explicitly need the unlock to occur before
> > > the slowpath tail flag is read.
> >
> > Well, just make the unlock do the actual real unlock operation
> > ("fastpath"), leaving the TICKET_SLOWPATH_FLAG alone. The unlock path
> > can *test* the flag and do whatever kicking it needs to get people
> > started again, but not clear it again.
>
> This is definitely a good idea, will think more on this.

Just sent the patch with that idea, also keeping in mind that
head = tail may not hold good for trylock checking
(last unlock might have left TICKET_SLOWPATH_FLAG set)

http://article.gmane.org/gmane.linux.kernel/1883900

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/