Re: [PATCH RT] fix or hrtimers (was: [ANNOUNCE] 2.6.15-rc5-hrt2 - hrtimers based high resolution patches)

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 2006-01-11 at 21:51 -0500, Steven Rostedt wrote:
> On Wed, 2006-01-11 at 21:14 -0500, Steven Rostedt wrote:
> > Finally!  I did it.  I have an updated timer_stress test at 
> > http://www.kihontech.com/tests/rt/timer_stress.c
> > that triggers the deadlock that I have been mentioning (and hit once in
> > my kernel).  But this time I hit it in 2.6.15-rt4-sr1 and got the
> > following output:
> 
> OK, it's not like me to just show a problem, without at least having
> some type of fix for it.  Since my last fix, was turned down, and
> looking into it further, I now understand why.
> 
> The patch below now makes hrtimer_start cancel the timer and lock the
> base in one action. It also checks to see if the timer is running, and
> if it is, it doesn't do anything.  It basically, tests to see if it
> should cancel the timer.
> 
> This is now included in my rt maintenance patches at:
> 
> http://home.stny.rr.com/rostedt/patches/patch-2.6.15-rt4-sr2
> 
> But I'll include this patch here too so that you can look at what I've
> done.
> 
> My test at http://www.kihontech.com/tests/rt/timer_stress.c hasn't
> killed this kernel yet.  But I'll run it all night on both a UP machine
> with the -P (posix timers) and without -P on a SMP machine (setitimer).

FYI,

The tests ran all night without a bug!  Now I'm switching the tests
(without -P on UP and with -P on SMP).

-- Steve