Messages in this thread | | | Date | Wed, 6 Jan 2016 13:25:17 +0100 | From | Jan Kara <> | Subject | Re: [PATCH 1/7] printk: Hand over printing to console if printing too long |
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On Wed 06-01-16 15:48:36, Sergey Senozhatsky wrote: > On (01/05/16 15:37), Jan Kara wrote: > > > How about setting 'sync_print' to 'true' in... > > > bust_spinlocks() /* only set to true */ > > > or > > > console_verbose() /* um... may be... */ > > > or > > > having a separate one-liner for that > > > > > > void console_panic_mode(void) > > > { > > > sync_print = true; > > > } > > > > > > and call it early in panic(), before we send out IPI_STOP. > > > > I like using console_verbose() for setting sync_print to true. That will > > likely be more reliable than using oops in progress. After all > > console_verbose() is used like console_panic_mode() anyway and in quite a > > few places so it is a reasonable match. > > another corner case. > > a quote from -mm a74b6533ead8 http://www.spinics.net/lists/linux-mm/msg98990.html > > : This patch reduces the probability of such a lockup by introducing a > : specialized kernel thread (oom_reaper) which tries to reclaim additional > : memory by preemptively reaping the anonymous or swapped out memory owned > : by the oom victim under an assumption that such a memory won't be needed > : when its owner is killed and kicked from the userspace anyway. There is > : one notable exception to this, though, if the OOM victim was in the > : process of coredumping the result would be incomplete. This is considered > : a reasonable constrain because the overall system health is more important > : than debugability of a particular application. > : > : A kernel thread has been chosen because we need a reliable way of > : invocation so workqueue context is not appropriate because all the workers > : might be busy (e.g. allocating memory). Kswapd which sounds like another > : good fit is not appropriate as well because it might get blocked on locks > : during reclaim as well. > > particularly this "workqueue context is not appropriate because all the workers > might be busy (e.g. allocating memory)" part. I think printk should switch to > sync mode in this case, since printk now does queue_work(system_wq, work). > um... console_verbose() call from oom kill? but it'll be nice to return back > to async mode once (if) memory pressure goes away.
Hum, yes, some mechanism to switch to sync printing in case work cannot be executed for a long time is probably needed. I'll think about it.
Honza -- Jan Kara <jack@suse.com> SUSE Labs, CR
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