On (12/22/16 11:53), Petr Mladek wrote:

quoted

Thank you. I tried "[PATCHv6 0/7] printk: use printk_safe to handle printk()
recursive calls" at https://lkml.org/lkml/2016/12/21/232 on top of linux.git
as of commit 52bce91165e5f2db "splice: reinstate SIGPIPE/EPIPE handling", but
it turned out that your patch set does not solve this problem.

I was assuming that sending to consoles from printk() is offloaded to a kernel
thread dedicated for that purpose, but your patch set does not do it. As a result,
somebody who called out_of_memory() is still preempted by other threads consuming
CPU time due to cond_resched() from console_unlock() as demonstrated by below patch.

Ah, it was a misunderstanding. The "printk_safe" patchset allows to
call printk() from inside some areas guarded by logbuf_lock. By other
words, it allows to print errors from inside printk() code. I does
not solve the soft-/live-locks.

ineeed.

We need the async printk patchset here. It will allow to offload the
console handling to the kthread. AFAIK, Sergey wanted to rebase it
on top of the printk_safe patchset. I am not sure when he want or
will have time to do so, though.

sure. this is still the case. and in fact my tree here
https://gitlab.com/senozhatsky/linux-next-ss/commits/printk-safe-deferred

contains both patch sets: 9 patche in total (rebased agains linux-next
20161221).

first 7 patches are printk-safe, the last 2 -- async printk.

	-ss

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