On 2/22/22 22:04, Baoquan He wrote:
On 02/09/22 at 02:57pm, 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().
This looks good to me, and the particularity of cpu hotplug can be
understood well by other code reader. Thanks.
Acked-by: Baoquan He <bhe@xxxxxxxxxx>
Thank you!
eric
Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
---
kernel/crash_core.c | 10 ++++++++++
kernel/kexec_file.c | 5 +++++
2 files changed, 15 insertions(+)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 524470e18883..b6942e04a188 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -550,6 +550,16 @@ 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) ?
+ (unsigned int)a : ~0U;
+
/* Now invoke arch-specific update handler */
arch_crash_hotplug_handler(kexec_crash_image, hp_action, a, b);
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 93bb0c0ce66c..339995d42169 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
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