[Linux-Xtensa] Re: [PATCH] time: sched_clock: fix integer overflow

Baruch Siach baruch at tkos.co.il
Sun Aug 11 20:03:29 PDT 2013


Hi Thomas, John,

On Mon, Jul 29, 2013 at 08:59:39AM +0300, Baruch Siach wrote:
> On Wed, Jul 17, 2013 at 12:46:53PM +0300, Baruch Siach wrote:
> > The expression '(1 << 32)' happens to evaluate as 0 on ARM, but it evaluates as
> > 1 on xtensa and x86_64. This zeros sched_clock_mask, and breaks sched_clock().
> > Set the type of 1 to 'unsigned long long' to get the value we need.
> 
> Ping? -rc3 is out, and this bug (which currently breaks xtensa) is not fixed 
> yet. Please consider applying.

Sorry to bother again, but -rc5 is here and xtensa sched_clock is still 
broken.

baruch

> > Reported-by: Max Filippov <jcmvbkbc at gmail.com>
> > Tested-by: Max Filippov <jcmvbkbc at gmail.com>
> > Acked-by: Russell King <rmk+kernel at arm.linux.org.uk>
> > Signed-off-by: Baruch Siach <baruch at tkos.co.il>
> > ---
> >  kernel/time/sched_clock.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
> > index a326f27..0b479a6 100644
> > --- a/kernel/time/sched_clock.c
> > +++ b/kernel/time/sched_clock.c
> > @@ -121,7 +121,7 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
> >  	BUG_ON(bits > 32);
> >  	WARN_ON(!irqs_disabled());
> >  	read_sched_clock = read;
> > -	sched_clock_mask = (1 << bits) - 1;
> > +	sched_clock_mask = (1ULL << bits) - 1;
> >  	cd.rate = rate;
> >  
> >  	/* calculate the mult/shift to convert counter ticks to ns. */
> > -- 

-- 
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