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Groups > linux.kernel > #1619853
| From | Petr Mladek <pmladek@suse.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage |
| Date | 2017-04-10 14:00 +0200 |
| Message-ID | <tuG9b-av-5@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <ttB1U-6XP-5@gated-at.bofh.it> <ttBuW-78a-13@gated-at.bofh.it> <ttDQ6-rS-29@gated-at.bofh.it> <tui6T-1tb-21@gated-at.bofh.it> <tuzAJ-4sI-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon 2017-04-10 13:53:39, Sergey Senozhatsky wrote:
> On (04/09/17 12:12), Pavel Machek wrote:
> [..]
> > > a side note,
> > > that's rather unclear to me how would "message delayed" really help.
> > > if your system hard-lockup so badly and there are no printk messages
> > > even from NMI watchdog, then we won't be able to print that message.
> >
> > We are talking about
> >
> > printk("unusual condition");
> > do_something_clever(); /* Which unfortunately hard-crashes the machine */
> >
> > that works with my proposal, but not with yours. Seen it happen many
> > times before.
>
> I see your point, sure.
> I can't completely agree on "that works with my proposal, but not with yours."
>
> on SMP system this would be true only if no other CPU holds the console_sem
> at the time we call printk(). (skipping irrelevant cases when we have suspended
> console or !online CPU and !CON_ANYTIME console). and there is nothing that
> makes "no other CPU holds the console_sem" always true on SMP system at any
> given point in time. so no, "A always works, B never works" is not accurate.
>
> but, once again, I see your point.
A compromise might be to move the offloading from vprintk_emit() to
console_unlock(). By other words, the printk could always try to
flush some messages to the console. The console might trigger
the offload (wakeup kthread) after few lines or when the printing
takes too long.
We could go even furter. We could replace the cond_resched() in
console_unlock() with a need_resched() check. Then we could avoid
sleeping with console_sem taken.
It will avoid the softlockups caused by printk(). It should
work pretty well in most critical situations.
Of course, it will not guarantee that we will see all messages when
there is a flood of messages from many CPUs. But it was never
guaranteed.
Best Regards,
Petr
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[RFC][PATCHv2 0/8] printk: introduce printing kernel thread Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:30 +0200
[RFC][PATCHv2 2/8] printk: introduce printing kernel thread Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:30 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Petr Mladek <pmladek@suse.com> - 2017-04-04 11:10 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-04 11:40 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Pavel Machek <pavel@ucw.cz> - 2017-04-06 19:20 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-07 07:20 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Pavel Machek <pavel@ucw.cz> - 2017-04-07 09:30 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-07 10:20 +0200
Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread Pavel Machek <pavel@ucw.cz> - 2017-04-07 14:10 +0200
[RFC][PATCHv2 5/8] sysrq: switch to printk.emergency mode in unsafe places Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:30 +0200
Re: [RFC][PATCHv2 5/8] sysrq: switch to printk.emergency mode in unsafe places Petr Mladek <pmladek@suse.com> - 2017-03-31 17:40 +0200
Re: [RFC][PATCHv2 5/8] sysrq: switch to printk.emergency mode in unsafe places Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-01 02:10 +0200
[RFC][PATCHv2 1/8] printk: move printk_pending out of per-cpu Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:40 +0200
Re: [RFC][PATCHv2 1/8] printk: move printk_pending out of per-cpu Petr Mladek <pmladek@suse.com> - 2017-03-31 15:20 +0200
Re: [RFC][PATCHv2 1/8] printk: move printk_pending out of per-cpu Peter Zijlstra <peterz@infradead.org> - 2017-03-31 15:40 +0200
Re: [RFC][PATCHv2 1/8] printk: move printk_pending out of per-cpu Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-03 13:30 +0200
Re: [RFC][PATCHv2 1/8] printk: move printk_pending out of per-cpu Petr Mladek <pmladek@suse.com> - 2017-04-03 14:50 +0200
[RFC][PATCHv2 6/8] kexec: switch to printk.emergency mode in unsafe places Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:40 +0200
Re: [RFC][PATCHv2 6/8] kexec: switch to printk.emergency mode in unsafe places Petr Mladek <pmladek@suse.com> - 2017-03-31 17:40 +0200
[RFC][PATCHv2 8/8] printk: enable printk offloading Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-03-31 04:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-03-31 06:10 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Ye Xiaolong <xiaolong.ye@intel.com> - 2017-03-31 08:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-31 16:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage ebiederm@xmission.com (Eric W. Biederman) - 2017-03-31 17:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Jan Kara <jack@suse.cz> - 2017-04-03 11:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Petr Mladek <pmladek@suse.com> - 2017-04-03 12:10 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-06 19:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-07 06:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-07 09:20 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-07 09:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-07 10:20 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-07 14:20 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-07 14:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Steven Rostedt <rostedt@goodmis.org> - 2017-04-07 16:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-07 17:20 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Peter Zijlstra <peterz@infradead.org> - 2017-04-07 17:30 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-07 17:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage ebiederm@xmission.com (Eric W. Biederman) - 2017-04-09 20:30 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-10 06:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-09 12:20 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-10 07:00 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Petr Mladek <pmladek@suse.com> - 2017-04-10 14:00 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-10 17:10 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-10 20:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-11 03:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-11 18:30 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-12 20:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-13 06:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-13 08:00 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-13 10:30 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Petr Mladek <pmladek@suse.com> - 2017-04-13 16:10 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-14 06:50 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Steven Rostedt <rostedt@goodmis.org> - 2017-04-07 16:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Pavel Machek <pavel@ucw.cz> - 2017-04-09 12:00 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-03 13:00 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Ye Xiaolong <xiaolong.ye@intel.com> - 2017-04-05 09:40 +0200
Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-05 10:50 +0200
Re: [RFC][PATCHv2 8/8] printk: enable printk offloading Petr Mladek <pmladek@suse.com> - 2017-04-03 17:50 +0200
Re: [RFC][PATCHv2 8/8] printk: enable printk offloading Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-04 14:30 +0200
[RFC][PATCHv2 4/8] pm: switch to printk.emergency mode in unsafe places Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:40 +0200
Re: [RFC][PATCHv2 4/8] pm: switch to printk.emergency mode in unsafe places Petr Mladek <pmladek@suse.com> - 2017-03-31 17:10 +0200
Re: [RFC][PATCHv2 4/8] pm: switch to printk.emergency mode in unsafe places Pavel Machek <pavel@ucw.cz> - 2017-04-06 19:30 +0200
Re: [RFC][PATCHv2 4/8] pm: switch to printk.emergency mode in unsafe places Andreas Mohr <andi@lisas.de> - 2017-04-09 13:00 +0200
Re: [RFC][PATCHv2 4/8] pm: switch to printk.emergency mode in unsafe places Petr Mladek <pmladek@suse.com> - 2017-04-10 14:30 +0200
Re: [RFC][PATCHv2 4/8] pm: switch to printk.emergency mode in unsafe places Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-04-10 16:40 +0200
[RFC][PATCHv2 7/8] printk: add printk emergency_mode parameter Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-03-29 11:40 +0200
Re: [RFC][PATCHv2 7/8] printk: add printk emergency_mode parameter Petr Mladek <pmladek@suse.com> - 2017-04-03 17:30 +0200
Re: [RFC][PATCHv2 7/8] printk: add printk emergency_mode parameter Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-04 10:30 +0200
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