Re: [PATCH] fix get_jiffies_64 to work on voyager

[Andrew Morton <akpm@osdl.org>]

James Bottomley <James.Bottomley@SteelEye.com> wrote:
>
> On Tue, 2004-01-06 at 10:19, Andrew Morton wrote:
> > Hm, OK.  I hit the same deadlock when running with the "don't require TSCs
> > to be synchronised in sched_clock()" patch from -mm.  The fix for that is
> > below.  I shall accelerate it.
> 
> Actually, I think we need to know why this is happening, since the use
> of these sequence locks is growing.

That would be nice.  Can you get a backtrace?

> On voyager I just put it down to HZ
> == 1000 being a bit much for my old pentium 66MHz processors, but if
> you've seen it on a much faster processor, that would tend to indicate
> there's some other problem at work here.

No, it was much simpler in my case: log_buf_len_setup() was accidentally
enabling interrupts early in boot and we were taking a timer interrupt
while holding a write lock on xtime_lock.  sched_clock() was requiring a
read lock and boom.