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Re: [PATCH] printk/nmi: restore printk_func in nmi_panic

From Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH] printk/nmi: restore printk_func in nmi_panic
Date 2016-02-27 04:40 +0100
Message-ID <r6DTz-5aO-9@gated-at.bofh.it> (permalink)
References <r6hq2-5F3-11@gated-at.bofh.it> <r6s25-4LU-9@gated-at.bofh.it> <r6CNP-4m4-1@gated-at.bofh.it> <r6DAd-53s-7@gated-at.bofh.it>
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On (02/27/16 12:09), Sergey Senozhatsky wrote:
> On (02/27/16 11:19), Sergey Senozhatsky wrote:
> [..]
> > > I think about a compromise. We should try to get the messages
> > > out only when kdump is not enabled.
> > 
> > can we zap_locks() if we are on nmi_panic()->panic()->console_flush_on_panic() path?
> > console_flush_on_panic() is happening after we send out smp_send_stop().
> 
> can something like this do the trick?

hm, no. it can't.

I forgot to move printk_nmi_exit() from nmi_panic() to panic(). so
it should have been:

	panic()
		...
		printk_nmi_exit()
		console_flush_on_panic()
			__zap_locks()
			printk_nmi_flush()
			console_unlock()

but this __zap_locks() can _in theory_ race with irq_work->printk_nmi_flush().
so we need something more than this...

	-ss

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Thread

[PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-26 04:40 +0100
  Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Petr Mladek <pmladek@suse.com> - 2016-02-26 16:00 +0100
    Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-27 03:30 +0100
      Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-27 04:20 +0100
        Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-27 04:40 +0100
          Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-28 05:00 +0100
      Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Petr Mladek <pmladek@suse.com> - 2016-02-29 11:40 +0100
        Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-29 12:20 +0100
          Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-01 10:30 +0100
            Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Petr Mladek <pmladek@suse.com> - 2016-03-01 12:10 +0100
              Re: [PATCH] printk/nmi: restore printk_func in nmi_panic Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-01 14:20 +0100

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