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@xxxxxxxxxx>
>
> Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: kexec@xxxxxxxxxxxxxxxxxxx
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: x86@xxxxxxxxxx
> Reported-by: Sachin P Bappalige <sachinpb@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
> ---
> Changelog:
>
> Since v1:
> - Keep the kexec_in_progress check within kexec_trylock() - Baoquan He
> - Include the reason why PowerPC brings offline CPUs online
> during the kexec kernel boot path - Baoquan He
> - Rebased on top of #next-20240910 to avoid conflict with the patch below
> https://lore.kernel.org/all/20240812041651.703156-1-sourabhjain@xxxxxxxxxxxxx/T/#u
>
> V2 RESEND:
> - Update linuxppc-dev mailing list address
> ---
> kernel/crash_core.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index c1048893f4b6..078fe5bc5a74 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -505,7 +505,8 @@ int crash_check_hotplug_support(void)
> crash_hotplug_lock();
> /* Obtain lock while reading crash information */
> if (!kexec_trylock()) {
> - pr_info("kexec_trylock() failed, kdump image may be inaccurate\n");
> + if (!kexec_in_progress)
> + pr_info("kexec_trylock() failed, kdump image may be inaccurate\n");
> crash_hotplug_unlock();
> return 0;
> }
> @@ -547,7 +548,8 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu,
> crash_hotplug_lock();
> /* Obtain lock while changing crash information */
> if (!kexec_trylock()) {
> - pr_info("kexec_trylock() failed, kdump image may be inaccurate\n");
> + if (!kexec_in_progress)
> + pr_info("kexec_trylock() failed, kdump image may be inaccurate\n");
> crash_hotplug_unlock();
> return;
> }
> --
> 2.46.0
>
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