On Wed, Mar 19, 2025 at 03:06:12PM +0100, Frederic Weisbecker wrote:
> Le Wed, Mar 19, 2025 at 12:07:07PM +0100, Thomas Bogendoerfer a écrit :
> > On Sat, Mar 15, 2025 at 08:40:02PM +0100, Marco Crivellari wrote:
> > > MIPS re-enables interrupts on its idle routine and performs
> > > a TIF_NEED_RESCHED check afterwards before putting the CPU to sleep.
> > >
> > > The IRQs firing between the check and the 'wait' instruction may set the
> > > TIF_NEED_RESCHED flag. In order to deal with this possible race, IRQs
> > > interrupting __r4k_wait() rollback their return address to the
> > > beginning of __r4k_wait() so that TIF_NEED_RESCHED is checked
> > > again before going back to sleep.
> > >
> > > However idle IRQs can also queue timers that may require a tick
> > > reprogramming through a new generic idle loop iteration but those timers
> > > would go unnoticed here because __r4k_wait() only checks
> > > TIF_NEED_RESCHED. It doesn't check for pending timers.
> >
> > can you give a commit ID, when this change got introduced ?
>
> That would be:
>
> Fixes: c65a5480ff29 ("[MIPS] Fix potential latency problem due to non-atomic cpu_wait.")
hmm, so even then checking TIF_NEED_RESCHED wasn't enough (we are talking
about 2.6.27) ?
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
