[PATCH v7 6/8] kexec: exclude hot remove cpu from elfcorehdr notes

Eric DeVolder
2022-04-14T22:31:02Z

On 4/13/22 21:48, Baoquan He wrote:
> On 04/13/22 at 12:42pm, Eric DeVolder wrote:
>> Due to use of CPUHP_AP_ONLINE_DYN, upon CPU unplug, the CPU is
>> still in the for_each_present_cpu() list when within the
>> crash_hotplug_handler(). Thus the CPU must be explicitly excluded
>> when building the new list of CPUs.
>>
>> This change identifies in crash_hotplug_handler() the CPU to be
>> excluded, and the check for excluding the CPU in
>> crash_prepare_elf64_headers().
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
>> Acked-by: Baoquan He <bhe@redhat.com>
>
> This patch is updated, the old ack should be removed. It looks better to
> put the offlinecpu assignment here.
ok

>
> Ack it again.
>
> Acked-by: Baoquan He <bhe@redhat.com>
thanks!
eric

>
>> ---
>> kernel/crash_core.c | 9 +++++++++
>> kernel/kexec_file.c | 5 +++++
>> 2 files changed, 14 insertions(+)
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index ecf746243ab2..036243b1f252 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -521,6 +521,15 @@ static void crash_hotplug_handler(unsigned int hp_action,
>> /* Flag to differentiate between normal load and hotplug */
>> kexec_crash_image->hotplug_event = true;
>>
>> + /*
>> + * Due to use of CPUHP_AP_ONLINE_DYN, upon unplug and during
>> + * this callback, the CPU is still in the for_each_present_cpu()
>> + * list. Must explicitly look to exclude this CPU when building
>> + * new list.
>> + */
>> + kexec_crash_image->offlinecpu =
>> + (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) ? cpu : ~0U;
>> +
>> /* Now invoke arch-specific update handler */
>> arch_crash_hotplug_handler(kexec_crash_image, hp_action, cpu);
>>
>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
>> index 94a459209111..9d5c4eea0179 100644
>> --- a/kernel/kexec_file.c
>> +++ b/kernel/kexec_file.c
>> @@ -1314,6 +1314,11 @@ int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
>>
>> /* Prepare one phdr of type PT_NOTE for each present CPU */
>> for_each_present_cpu(cpu) {
>> +#ifdef CONFIG_CRASH_HOTPLUG
>> + /* Skip the soon-to-be offlined cpu */
>> + if (image->hotplug_event && (cpu == image->offlinecpu))
>> + continue;
>> +#endif
>> phdr->p_type = PT_NOTE;
>> notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
>> phdr->p_offset = phdr->p_paddr = notes_addr;
>> --
>> 2.27.0
>>
>