Messages in this thread | | | Date | Fri, 7 Mar 2003 14:20:48 +0100 | From | Jens Axboe <> | Subject | Re: 2.5.64 and jiffies wrap |
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On Fri, Mar 07 2003, Andrew Morton wrote: > Jens Axboe <axboe@suse.de> wrote: > > > > Hi, > > > > The patch doesn't look right, why is INITIAL_JIFFIES being cast to > > unsigned int? This breaks x86_64 at least. > > > > ... > > -#define INITIAL_JIFFIES ((unsigned int) (-300*HZ)) > > This sets the initial jiffies value to 0x00000000fffb6c20, which can trigger > 32-bit wraparound bugs: if some random jiffy counter wraps from > 0x00000000ffffffff to 0x0000000000000000 then things fail. > > davem was bitten by at least one such bug in the qlogicfc driver. It would > have caused 64-bit machines to fail after 49 days. > > It turns out that it is more valuable to test for this than to test for > 64-bit wraparound bugs.
Ok makes sense, I thought the point was just to test for jiffies wrap. Anyways, the patch breaks boot on x86_64 here.
-- Jens Axboe
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