Messages in this thread | | | Date | Tue, 22 Mar 2016 02:11:05 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC][PATCH v5 1/2] printk: Make printk() completely async |
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On (03/21/16 16:33), Jan Kara wrote: [..] > > > And by calling wake_up_process() under logbuf_lock, you actually introduce > > > recursion issues for printk_deferred() messages which are supposed to be > > > working from under rq->lock and similar. So I think you have to keep this > > > section outside of logbuf_lock. > > > > hm, in_sched (printk_deferred()) messages are printed by > > irq work->wake_up_klogd_work_func(), not by wake_up_process() > > from vprintk_emit(). or am I missing something? > > Think of following: > > some function > printk() > vprintk_emit() > spin_lock(&logbuf_lock); > ... > wake_up_process() > printk_deferred() > vprintk_emit() -> recursion on logbuf_lock
uh, indeed. I was more concerned about printk() calls that are troublemakers and are already in wake_up_process() - spin_dump()s. but yes, braking printk_deferred() in this case is a regression. thanks for pointing that out. and also thanks to Byungchul.
-ss
> Previously scheduler code was allowed to call printk_deferred() wherever it > wanted... > > So we are not supposed to call into the scheduler from under logbuf_lock... > > Honza > -- > Jan Kara <jack@suse.com> > SUSE Labs, CR >
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