On 06/22, Steven Rostedt wrote:
>
> > truct tasklet_struct, work);
> > > +
> > > + if (unlikely(atomic_read(&t->count))) {
> > > + pr_debug("tasklet disabled %s %p\n", t->n, t);
> > > + set_bit(TASKLET_STATE_PENDING, &t->state);
> > > + smp_mb();
> > > + /* make sure we were not just enabled */
> > > + if (likely(atomic_read(&t->count)))
> > > + goto out;
> > > + clear_bit(TASKLET_STATE_PENDING, &t->state);
Looking closer, I think this is not right, and the smp_mb__before_clear_bit()
can't help.
/* t->count == 1 */
work_tasklet_exec() tasklet_enable()
...
set_bit(TASKLET_STATE_PENDING);
atomic_dec_and_test(&t->count);
/* t->count == 0 */
// False
if (atomic_read(&t->count))
goto out;
// True
if
(test_and_clear_bit(_PENDING))
tasklet_schedule();
clear_bit(TASKLET_STATE_PENDING);
execute t->func();
So, t->func() will be executed twice because tasklet_enable() does
tasklet_schedule().
So I think we need a fix for work_tasklet_exec,
- clear_bit(TASKLET_STATE_PENDING);
+ if (!test_and_clear_bit(TASKLET_STATE_PENDING))
goto out;
Steven, a very stupid suggestion, could you move the code for tasklet_enable()
up, closer to tasklet_disable() ?
Oleg.
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