Re: Killing tasklet from interrupt

[Maksim Krasnyanskiy <maxk@qualcomm.com>]

Did it help ?

>> > Sounds like what you need is tasklet_disable.
>> > tasklet_kill needs process context so you can't use it in timer.
>> >
>> > >It's a shame that the code doesn't explitely allow for it (i.e. you will
>> > >deadlock every time
>> > >in tasklet_unlock_wait(t);).
>> > Use tasklet_disable_nosync within the tasklet itself.
>>
>>         Well. I thought about that. Not possible.
>>         tasklet_disable is not the answer, because if the tasklet was
>>scheduled, it will stay forever in the tasklet queue. Also, I need to
>>forget forever about getting rid of the tasklet within the tasklet
>>itself, because it will just crash.
>How about something like this ?
>
>void tasklet_kill_from_interrupt(struct tasklet_struct *t)
>{
>         while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state));
>         tasklet_unlock_wait(t);
>}
>
>So, in your timer you would do:
>         set_bit(CLOSING_PLEASE_DONT_SCHEDULE_ANYTHING, something->state);
>         tasklet_kill_from_interrupt(something->tasklet);
>         /* cleanup/kfree/etc */
>
>>         Look below, comments by me (you've got to love uncommented
>>code). So, it's not today that I will use tasklets.
>Well, I use them without any problems in Bluetooth code. May be you should
>redesign your code a bit. For example don't kill tasklets from the timer.
>
>>P.S. : By the way, regarding flow control between TCP and netdevice
>>(our previous e-mail exchange with Paul), have you investigated the
>>effect of skb->destructor; (for example sock_wfree()).
>I'm sorry I must have missed skb->destructor part. How sock_wfree could 
>affect flow ctl between TCP and netdev ?
>sock_wfree just wakes up process sleeping in sock_alloc_send_skb or alike.
>
>>-------------------------------------------------------------
>>
>>static void tasklet_action(struct softirq_action *a)
>>{
>>         int cpu = smp_processor_id();
>>         struct tasklet_struct *list;
>>
>>         local_irq_disable();
>>         list = tasklet_vec[cpu].list;
>>         tasklet_vec[cpu].list = NULL;
>>         local_irq_enable();
>>
>>         while (list) {
>>                 struct tasklet_struct *t = list;
>>
>>                 list = list->next;
>>
>>                 if (tasklet_trylock(t)) {
>>                         if (!atomic_read(&t->count)) {
>>                                 if 
>> (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
>>                                         BUG();
>>         // Call tasklet handler
>>                                 t->func(t->data);
>>         // If tasklet was killed/destroyed/kfree above, we will die
>>                                 tasklet_unlock(t);
>>                                 continue;
>>                         }
>>                         tasklet_unlock(t);
>>                 }
>"kill" means "wait until tasklet terminates and is not in the queue". So 
>it's not a problem
>And you would not want to destroy _locked_ tasklet. You'd wait until it's 
>unlocked.
>
>Max