linux-kernel - Re: [PATCH RESEND v2] kexec/crash: no crash update when kexec in progress

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Message-ID: <ZuKnwcqv9xQDNOrl@MiWiFi-R3L-srv>
Date: Thu, 12 Sep 2024 16:35:13 +0800
From: Baoquan He <bhe@...hat.com>
To: Sourabh Jain <sourabhjain@...ux.ibm.com>, akpm@...ux-foundation.org
Cc: Hari Bathini <hbathini@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>, kexec@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, Sachin P Bappalige <sachinpb@...ux.vnet.ibm.com>
Subject: Re: [PATCH RESEND v2] kexec/crash: no crash update when kexec in
 progress

On 09/12/24 at 01:33pm, Sourabh Jain wrote:
> Hello Baoquan,
> 
> On 11/09/24 19:50, Baoquan He wrote:
> > On 09/11/24 at 04:51pm, Sourabh Jain wrote:
> > > The following errors are observed when kexec is done with SMT=off on
> > > powerpc.
> > > 
> > > [  358.458385] Removing IBM Power 842 compression device
> > > [  374.795734] kexec_core: Starting new kernel
> > > [  374.795748] kexec: Waking offline cpu 1.
> > > [  374.875695] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate
> > > [  374.935833] kexec: Waking offline cpu 2.
> > > [  375.015664] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate
> > > snip..
> > > [  375.515823] kexec: Waking offline cpu 6.
> > > [  375.635667] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate
> > > [  375.695836] kexec: Waking offline cpu 7.
> > > 
> > > To avoid kexec kernel boot failure on PowerPC, all the present CPUs that
> > > are offline are brought online during kexec. For more information, refer
> > > to commit e8e5c2155b00 ("powerpc/kexec: Fix orphaned offline CPUs across
> > > kexec"). Bringing the CPUs online triggers the crash hotplug handler,
> > > crash_handle_hotplug_event(), to update the kdump image. Since the
> > > system is on the kexec kernel boot path and the kexec lock is held, the
> > > crash_handle_hotplug_event() function fails to acquire the same lock to
> > > update the kdump image, resulting in the error messages mentioned above.
> > > 
> > > To fix this, return from crash_handle_hotplug_event() without printing
> > > the error message if kexec is in progress.
> > > 
> > > The same applies to the crash_check_hotplug_support() function. Return
> > > 0 if kexec is in progress because kernel is not in a position to update
> > > the kdump image.
> > LGTM, thanks.
> > 
> > Acked-by: Baoquan he <bhe@...hat.com>
> 
> Thank you for the Ack!
> 
> My understanding is that this patch will go upstream via the linux-next
> tree, as it is based on
> https://lore.kernel.org/all/20240902034708.88EC1C4CEC2@smtp.kernel.org/
> which is already part of the linux-next master branch. - Sourabh Jain

Then you should mark it as [PATCH linux-next] in subject.

Since this patch is in generic code, it needs Andrew's help to
pick it. Let's wait and see if Andrew need a new post to change
the subject.

Thanks
Baoquan