The patch titled Subject: tasklet: ignore disabled tasklet in tasklet_action() has been added to the -mm tree. Its filename is tasklet-ignore-disabled-tasklet-in-tasklet_action.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Xiaotian Feng <xtfeng@xxxxxxxxx> Subject: tasklet: ignore disabled tasklet in tasklet_action() We met a ksoftirqd 100% issue, the perf top shows kernel is busy with tasklet_action(), but no actual action is shown. From dumped kernel, there's only one disabled tasklet on the tasklet_vec. tasklet_action might be handled after tasklet is disabled, this will make disabled tasklet stayed on tasklet_vec. tasklet_action will not handle disabled tasklet, but place it on the tail of tasklet_vec, still raise softirq for this tasklet. Things will become worse if device driver uses tasklet_disable on its device remove/close code. The disabled tasklet will stay on the vec, frequently __raise_softirq_off() and make ksoftirqd wakeup even if no tasklets need to be handled. This patch introduced a new TASKLET_STATE_HI bit to indicate HI_SOFTIRQ, in tasklet_action(), simply ignore the disabled tasklet and don't raise the softirq nr. In my previous patch, I remove tasklet_hi_enable() since it is the same as tasklet_enable(). So only tasklet_enable() needs to be modified, if tasklet state is changed from disable to enable, use __tasklet_schedule() to put it on the right vec. Signed-off-by: Xiaotian Feng <dannyfeng@xxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/interrupt.h | 12 ++++++++++-- kernel/softirq.c | 8 ++++---- 2 files changed, 14 insertions(+), 6 deletions(-) diff -puN include/linux/interrupt.h~tasklet-ignore-disabled-tasklet-in-tasklet_action include/linux/interrupt.h --- a/include/linux/interrupt.h~tasklet-ignore-disabled-tasklet-in-tasklet_action +++ a/include/linux/interrupt.h @@ -521,7 +521,8 @@ struct tasklet_struct name = { NULL, 0, enum { TASKLET_STATE_SCHED, /* Tasklet is scheduled for execution */ - TASKLET_STATE_RUN /* Tasklet is running (SMP only) */ + TASKLET_STATE_RUN, /* Tasklet is running (SMP only) */ + TASKLET_STATE_HI /* Tasklet is HI_SOFTIRQ */ }; #ifdef CONFIG_SMP @@ -593,7 +594,14 @@ static inline void tasklet_disable(struc static inline void tasklet_enable(struct tasklet_struct *t) { smp_mb__before_atomic_dec(); - atomic_dec(&t->count); + if (atomic_dec_and_test(&t->count)) { + if (!test_bit(TASKLET_STATE_SCHED, &t->state)) + return; + if (test_bit(TASKLET_STATE_HI, &t->state)) + __tasklet_hi_schedule(t); + else + __tasklet_schedule(t); + } } static inline void tasklet_hi_enable(struct tasklet_struct *t) diff -puN kernel/softirq.c~tasklet-ignore-disabled-tasklet-in-tasklet_action kernel/softirq.c --- a/kernel/softirq.c~tasklet-ignore-disabled-tasklet-in-tasklet_action +++ a/kernel/softirq.c @@ -431,6 +431,7 @@ void __tasklet_hi_schedule(struct taskle *__this_cpu_read(tasklet_hi_vec.tail) = t; __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); raise_softirq_irqoff(HI_SOFTIRQ); + set_bit(TASKLET_STATE_HI, &t->state); local_irq_restore(flags); } @@ -442,6 +443,7 @@ void __tasklet_hi_schedule_first(struct t->next = __this_cpu_read(tasklet_hi_vec.head); __this_cpu_write(tasklet_hi_vec.head, t); + set_bit(TASKLET_STATE_HI, &t->state); __raise_softirq_irqoff(HI_SOFTIRQ); } @@ -467,10 +469,9 @@ static void tasklet_action(struct softir if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) BUG(); t->func(t->data); - tasklet_unlock(t); - continue; } tasklet_unlock(t); + continue; } local_irq_disable(); @@ -502,10 +503,9 @@ static void tasklet_hi_action(struct sof if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) BUG(); t->func(t->data); - tasklet_unlock(t); - continue; } tasklet_unlock(t); + continue; } local_irq_disable(); _ Patches currently in -mm which might be from xtfeng@xxxxxxxxx are linux-next.patch tasklet-ignore-disabled-tasklet-in-tasklet_action.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html