Messages in this thread | | | Subject | Re: [PATCH RT] tasklet/rt: Prevent tasklets from going into infinite spin in RT | From | Mike Galbraith <> | Date | Wed, 30 Nov 2011 13:45:30 +0100 |
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On Wed, 2011-11-30 at 11:24 +0100, Thomas Gleixner wrote: > On Wed, 30 Nov 2011, Mike Galbraith wrote:
> > @@ -486,12 +495,43 @@ extern void softirq_check_pending_idle(v > > */ > > DECLARE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); > > > > -DECLARE_PER_CPU(struct task_struct *, ksoftirqd); > > +struct softirqdata { > > + int mask; > > + struct task_struct *tsk; > > +}; > > + > > +DECLARE_PER_CPU(struct softirqdata [NR_SOFTIRQ_THREADS], ksoftirqd); > > + > > +static inline bool this_cpu_ksoftirqd(struct task_struct *p) > > +{ > > + int i; > > + > > + for (i = 0; i < NR_SOFTIRQ_THREADS; i++) { > > + if (p == __get_cpu_var(ksoftirqd)[i].tsk) > > + return true; > > You are not serious about that loop, are you ?
Well, it's a short loop, especially when NR_SOFTIRQ_THREADS = 1 (poof).
> > @@ -131,11 +155,18 @@ void softirq_check_pending_idle(void) > > */ > > static void wakeup_softirqd(void) > > { > > - /* Interrupts are disabled: no need to stop preemption */ > > - struct task_struct *tsk = __this_cpu_read(ksoftirqd); > > + struct task_struct *tsk; > > + u32 pending = local_softirq_pending(), mask, i; > > > > - if (tsk && tsk->state != TASK_RUNNING) > > - wake_up_process(tsk); > > + /* Interrupts are disabled: no need to stop preemption */ > > + for (i = 0; pending && i < NR_SOFTIRQ_THREADS; i++) { > > + mask = __get_cpu_var(ksoftirqd)[i].mask; > > + if (!(pending & mask)) > > + continue; > > + tsk = __get_cpu_var(ksoftirqd)[i].tsk; > > + if (tsk && tsk->state != TASK_RUNNING) > > + wake_up_process(tsk); > > + } > > } > > Dammned serious is seems. :)
Deadly serious :)
For the problem at hand (timer wakeups), NR_SOFTIRQ_THREADS could be 2.
> I was looking into that as well, though I did not want to inflict it > on 3.0 at this point. > > Thanks, > > tglx
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