RE: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) belowsmp_send_stop()

[Seiji Aguchi]

>Aren't you worried about the comment about smp_send_stop() not
>being hardened to work in a panic situation?
> 	/*
> 	 * Note smp_send_stop is the usual smp shutdown function, which
> 	 * unfortunately means it may not be hardened to work in a panic

This comment is wrong because Don improved smp_send_stop() by switching REBOOT_VECTOR to NMI.
And his patch has already merged to linux-next tree.

http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=commitdiff;h=3603a2512f9e69dc87914ba922eb4a0812b21cd6

So, current smp_send_stop() is hardened to work in a panic situation.

I will remove this wrong comment.

Seiji

>-----Original Message-----
>From: Luck, Tony [mailto:tony.luck@xxxxxxxxx]
>Sent: Thursday, January 05, 2012 2:07 PM
>To: Seiji Aguchi; Don Zickus
>Cc: linux-kernel@xxxxxxxxxxxxxxx; Matthew Garrett; Vivek Goyal; Chen, Gong; akpm@xxxxxxxxxxxxxxxxxxxx; Brown, Len;
>'ying.huang@xxxxxxxxx'; 'ak@xxxxxxxxxxxxxxx'; 'hughd@xxxxxxxxxxxx'; 'mingo@xxxxxxx'; jmorris@xxxxxxxxx;
>a.p.zijlstra@xxxxxxxxx; namhyung@xxxxxxxxx; dle-develop@xxxxxxxxxxxxxxxxxxxxx; Satoru Moriya
>Subject: RE: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop()
>
>-	kmsg_dump(KMSG_DUMP_PANIC);
>-
> 	/*
> 	 * Note smp_send_stop is the usual smp shutdown function, which
> 	 * unfortunately means it may not be hardened to work in a panic
>@@ -117,6 +115,8 @@ void panic(const char *fmt, ...)
> 	 */
> 	smp_send_stop();
>
>+	kmsg_dump(KMSG_DUMP_PANIC);
>+
>
>Aren't you worried about the comment about smp_send_stop() not
>being hardened to work in a panic situation?
>
>If it does work - we are clearly much better off moving the
>kmsg_dump() call down like this. It makes life much simpler
>and cleaner to work with just one running cpu.
>
>But if something goes wrong - we might not see the dump at all!
>
>How do we compare these cases and decide that it is better to
>trust that smp_send_stop() will return?
>
>-Tony
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