Messages in this thread | | | Date | Wed, 17 Oct 2012 18:26:13 +0400 | From | Stanislav Kinsbursky <> | Subject | Re: [RFC PATCH v2] posix timers: allocate timer id per task |
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17.10.2012 17:57, Eric Dumazet пишет: > On Wed, 2012-10-17 at 17:18 +0400, Stanislav Kinsbursky wrote: > >> +static int posix_timer_add(struct k_itimer *timer) >> +{ >> + struct signal_struct *sig = current->signal; >> + int next_free_id = sig->posix_timer_id; >> + struct hlist_head *head; >> + int ret = -ENOENT; >> + >> + do { >> + spin_lock(&hash_lock); >> + head = &posix_timers_hashtable[hash(sig, sig->posix_timer_id)]; >> + if (__posix_timers_find(head, sig, sig->posix_timer_id) == NULL) { >> + hlist_add_head_rcu(&timer->t_hash, head); > > Hmm... > >> + ret = sig->posix_timer_id++; >> + } else { >> + if (++sig->posix_timer_id < 0) >> + sig->posix_timer_id = 0; >> + if (sig->posix_timer_id == next_free_id) >> + ret = -EAGAIN; >> + } >> + spin_unlock(&hash_lock); >> + } while (ret == -ENOENT); >> + return ret; >> +} >> + > > You probably need to add a rcu_assign_pointer() or smp_wmb() before > the : > > new_timer->it_signal = current->signal; > > in the following block : > > spin_lock_irq(¤t->sighand->siglock); > new_timer->it_signal = current->signal; > list_add(&new_timer->list, ¤t->signal->posix_timers); > spin_unlock_irq(¤t->sighand->siglock); > > Or else another thread can read outdated informations... > > > spin_lock_irq(¤t->sighand->siglock); > list_add(&new_timer->list, ¤t->signal->posix_timers); > spin_unlock_irq(¤t->sighand->siglock); > smp_wmb(); > new_timer->it_signal = current->signal; > >
Sorry, but I don't understand what races you are talking about. Could you specify, please?
-- Best regards, Stanislav Kinsbursky -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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