Messages in this thread | | | Date | Thu, 5 Jan 2012 16:01:23 -0500 | From | Don Zickus <> | Subject | Re: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop() |
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On Thu, Jan 05, 2012 at 03:10:25PM -0500, Seiji Aguchi wrote: > > >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.
I only fixed x86. Who knows what the other arches do..
I don't know how to prove something is hardened other than not seeing any hangs or false reboots on in that piece of code.
Cheers, Don
> > 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@intel.com] > >Sent: Thursday, January 05, 2012 2:07 PM > >To: Seiji Aguchi; Don Zickus > >Cc: linux-kernel@vger.kernel.org; Matthew Garrett; Vivek Goyal; Chen, Gong; akpm@linux-foundation.org; Brown, Len; > >'ying.huang@intel.com'; 'ak@linux.intel.com'; 'hughd@chromium.org'; 'mingo@elte.hu'; jmorris@namei.org; > >a.p.zijlstra@chello.nl; namhyung@gmail.com; dle-develop@lists.sourceforge.net; 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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