john stultz wrote: > > The following additional patch should correct this issue. Although since > we weren't actually hitting it, the issue is a bit theoretical, so I've > not been able to prove it really fixes anything.
Could you please look at the message below? I sent it privately near a month ago, but I think these problems are not fixed yet. Oleg. --------------------------------------------------------------------------- > +__tasklet_action(struct softirq_action *a, struct tasklet_struct *list) > +{ > + int loops = 1000000; > > while (list) { > struct tasklet_struct *t = list; > > list = list->next; > + /* > + * Should always succeed - after a tasklist got on the > + * list (after getting the SCHED bit set from 0 to 1), > + * nothing but the tasklet softirq it got queued to can > + * lock it: > + */ > + if (!tasklet_trylock(t)) { > + WARN_ON(1); > + continue; > + } > + > + t->next = NULL; > + > + /* > + * If we cannot handle the tasklet because it's disabled, > + * mark it as pending. tasklet_enable() will later > + * re-schedule the tasklet. > + */ > + if (unlikely(atomic_read(&t->count))) { > +out_disabled: > + /* implicit unlock: */ > + wmb(); > + t->state = TASKLET_STATEF_PENDING; What if tasklet_enable() happens just before this line ? After the next schedule_tasklet() we have all bits set: SCHED, RUN, PENDING. The next invocation of __tasklet_action() clears SCHED, but tasklet_tryunlock() below can never succeed because of PENDING. > +again: > + t->func(t->data); > + > + /* > + * Try to unlock the tasklet. We must use cmpxchg, because > + * another CPU might have scheduled or disabled the tasklet. > + * We only allow the STATE_RUN -> 0 transition here. > + */ > + while (!tasklet_tryunlock(t)) { > + /* > + * If it got disabled meanwhile, bail out: > + */ > + if (atomic_read(&t->count)) > + goto out_disabled; > + /* > + * If it got scheduled meanwhile, re-execute > + * the tasklet function: > + */ > + if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) > + goto again; TASKLET_STATE_SCHED could be set by tasklet_kill(), in this case it is not nice to call t->func() again (but probably harmless). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/