Messages in this thread | | | Date | Wed, 11 Jan 2023 08:32:42 +0100 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH v1] net/dev.c : Remove redundant state settings after waking up |
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On 2023-01-10 16:42:56 [-0800], Wei Wang wrote: > I was not able to see the entire changelog, but I don't think > > - set_current_state(TASK_INTERRUPTIBLE); > is redundant. > > It makes sure that if the previous if statement: > if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state) || woken) > is false, this napi thread yields the CPU to other threads waiting to > be run by calling schedule().
It made sense in the beginning but now the suggested patch is a clean up. First the `woken' parameter was added in commit cb038357937ee ("net: fix race between napi kthread mode and busy poll")
and then the `napi_disable_pending' check was removed in commit 27f0ad71699de ("net: fix hangup on napi_disable for threaded napi")
which renders the code to: | while (!kthread_should_stop()) { | if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state) || woken) { | WARN_ON(!list_empty(&napi->poll_list)); | __set_current_state(TASK_RUNNING); | return 0; | } | | schedule(); | /* woken being true indicates this thread owns this napi. */ | woken = true; | set_current_state(TASK_INTERRUPTIBLE); | } | __set_current_state(TASK_RUNNING);
so when you get out of schedule() woken is set and even if NAPI_STATE_SCHED_THREADED is not set, the while() loop is left due to `woken = true'. So changing state to TASK_INTERRUPTIBLE makes no sense since it will be set back to TASK_RUNNING cycles later.
Sebastian
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