Messages in this thread | | | Date | Wed, 16 Mar 2016 16:56:05 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC][PATCH v4 1/2] printk: Make printk() completely async |
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On (03/16/16 16:30), Byungchul Park wrote: > > Do you mean the wake_up_process() in console_unlock?
no, I meant wake_up_process(printk_kthread), the newly added one.
-- if we are going to have wake_up_process() in wake_up_klogd_work_func(), then we need `in_sched' message to potentially trigger a recursion chain
wake_up_klogd_work_func()->wake_up_process()->printk()->wake_up_process()->printk()...
to break this printk()->wake_up_process()->printk(), we need wake_up_process() to be under the logbuf lock; so vprintk_emit()'s if (logbuf_cpu == this_cpu) will act.
-- if we are going to have wake_up_process() in console_unlock(), then
console_unlock()->{up(), wake_up_process()}->printk()->{console_lock(), console_unlock()}->{up(), wake_up_process()}->printk()...
is undetectable... by the time console_unlock() calls wake_up_process() there are no printk() locks that this CPU owns.
> I said they should be kept *out of* the critical section. :-) > Otherwise, it can recurse us forever.
can you explain?
-ss
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