Patchwork [v11,4/5] core: Add kernel message dumper to call on oopses and panics

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Submitter Artem Bityutskiy
Date Oct. 24, 2009, 5:05 p.m.
Message ID <1256403957.29885.357.camel@localhost>
Download mbox | patch
Permalink /patch/36845/
State New, archived
Headers show


Artem Bityutskiy - Oct. 24, 2009, 5:05 p.m.
On Fri, 2009-10-23 at 18:53 +0300, Shargorodsky Atal
(EXT-Teleca/Helsinki) wrote:
> Hi all,
> On Thu, 2009-10-22 at 08:25 +0200, ext Simon Kagstrom wrote:
> > Thanks to everyone for the reviewing and suggestions!
> > 
> I have a couple of questions:
> 1. If somebody writes a module that uses dumper for uploading the
> oopses/panics logs via some pay-per-byte medium,  since he has no way
> to know in a module if the panic_on_oops flag is set, he'll have
> to upload both oops and the following panic, because he does not
> know for sure that the panic was caused by the oops. Hence he
> pays twice for the same information, right?

Looks like a valid point to me. Indeed, in this case we will first call
'kmsg_dump(KMSG_DUMP_OOPS)' from 'oops_exit()', and then call it from
'panic()'. And the dumper may dump the same information, which is not

I've looked briefly and tried to figure out how to fix this. But I
cannot find an clean way. And I was confused by the die/oops/etc code.
My question is, why the code does not work the following way instead?

If the code worked like this, I think the problem indicated by Atal
could be easily fixed.

> 2. We tried to use panic notifiers mechanism to print additional
> information that we want to see in mtdoops logs and it worked well,
> but having the kmsg_dump(KMSG_DUMP_PANIC) before the
> atomic_notifier_call_chain() breaks this functionality.
> Can we the call kmsg_dump() after the notifiers had been invoked?

Atal, I think you should just attach your patch, it is easier to express
what you mean.

But for me it looks like atomic_notifier_call_chain() can be moved up.

Anyway, please, show your patch.


diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 2d8a371..8f322c7 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -235,13 +235,12 @@  void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)

-       if (!signr)
-               return;
        if (in_interrupt())
                panic("Fatal exception in interrupt");
        if (panic_on_oops)
                panic("Fatal exception");
-       do_exit(signr);
+       if (signr)
+               do_exit(signr);

 int __kprobes __die(const char *str, struct pt_regs *regs, long err)