Messages in this thread | | | Date | Thu, 29 Sep 2005 18:46:36 -0700 | From | "Paul E. McKenney" <> | Subject | Re: 2.6.13-rc6-rt9 |
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On Fri, Sep 30, 2005 at 03:07:29AM +0200, Thomas Gleixner wrote: > On Thu, 2005-09-29 at 18:00 -0700, Paul E. McKenney wrote: > > > Even with a current -rt (2.6.14-rc2-rt5) UML does not run. The issue is > > > indeed (as jeff pointed out) that VTALRM is never send. The small test > > > programm below illustrates this. > > > > > > On a non-rt kernel it completed in 1 second. > > > On a -rt kernel it waits at infinitum. > > > > Will play with it and see what I broke... > > Paul, > > you are not the culprit :)
Woo-hoo!!! Exonerated!!! This time, anyway... ;-)
> The run_posix_cpu_timers(p) call is #ifdef'd out with PREEMPT_RT. > > Thats a hard to fix issue. > > It can not be run from hardirq context, as it takes a lot of locks > (especially our favorites: tasklist_lock and sighand->siglock). :( > > Maybe another playground for rcu, but it might also be solved by some > other mechanism for accounting and delayed execution in the PREEMPT_RT > case.
Certainly check_thread_timers() and check_process_timers() are playing with a number of task_struct fields, so it is not immediately clear to me how to safely replace tasklist_lock with RCU, at least not with a simple and small patch.
What did you have in mind for delayed execution?
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