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

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Message-ID: <Zqs8veRya7v/pXEt@MiWiFi-R3L-srv>
Date: Thu, 1 Aug 2024 15:43:57 +0800
From: Baoquan He <bhe@...hat.com>
To: Sourabh Jain <sourabhjain@...ux.ibm.com>
Cc: Hari Bathini <hbathini@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>, kexec@...ts.infradead.org,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, Sachin P Bappalige <sachinpb@...ux.vnet.ibm.com>
Subject: Re: [PATCH] kexec/crash: no crash update when kexec in progress

On 07/31/24 at 08:57pm, 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.
> 
> During kexec, the offline CPUs are brought online, which triggers the

Is this a generic action or specific on ppc about the offline CPUs being
brought line during kexec? 

> crash hotplug handler `crash_handle_hotplug_event()` to update the kdump
> image. Given that the system is on the kexec path and the kexec lock is
> taken, the `crash_handle_hotplug_event()` function fails to take the
> same lock to update the kdump image, resulting in the above error
> messages.
> 
> To fix this, let's return from `crash_handle_hotplug_event()` if kexec
> is in progress.
> 
> The same applies to the `crash_check_hotplug_support()` function.
> Return 0 if kexec is in progress.
> 
> Cc: Hari Bathini <hbathini@...ux.ibm.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: kexec@...ts.infradead.org
> Cc: linuxppc-dev@...abs.org
> Cc: linux-kernel@...r.kernel.org
> Cc: x86@...nel.org
> Reported-by: Sachin P Bappalige <sachinpb@...ux.vnet.ibm.com>
> Signed-off-by: Sourabh Jain <sourabhjain@...ux.ibm.com>
> ---
>  kernel/crash_core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 63cf89393c6e..d37a16d5c3a1 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -502,6 +502,9 @@ int crash_check_hotplug_support(void)
>  {
>  	int rc = 0;
>  
> +	if (kexec_in_progress)
> +		return 0;
> +
>  	crash_hotplug_lock();
>  	/* Obtain lock while reading crash information */
>  	if (!kexec_trylock()) {
> @@ -537,6 +540,9 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu,
>  {
>  	struct kimage *image;
>  
> +	if (kexec_in_progress)
> +		return;
> +
>  	crash_hotplug_lock();
>  	/* Obtain lock while changing crash information */
>  	if (!kexec_trylock()) {
> -- 
> 2.45.2
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 

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