The quilt patch titled Subject: Crash: add lock to serialize crash hotplug handling has been removed from the -mm tree. Its filename was crash-add-lock-to-serialize-crash-hotplug-handling.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------ From: Baoquan He bhe@redhat.com Subject: Crash: add lock to serialize crash hotplug handling Date: Tue, 26 Sep 2023 20:09:05 +0800

Eric reported that handling corresponding crash hotplug event can be failed easily when many memory hotplug event are notified in a short period. They failed because failing to take __kexec_lock.

======= [ 78.714569] Fallback order for Node 0: 0 [ 78.714575] Built 1 zonelists, mobility grouping on. Total pages: 1817886 [ 78.717133] Policy zone: Normal [ 78.724423] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 78.727207] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 80.056643] PEFILE: Unsigned PE binary =======

The memory hotplug events are notified very quickly and very many, while the handling of crash hotplug is much slower relatively. So the atomic variable __kexec_lock and kexec_trylock() can't guarantee the serialization of crash hotplug handling.

Here, add a new mutex lock __crash_hotplug_lock to serialize crash hotplug handling specifically. This doesn't impact the usage of __kexec_lock.

Link: https://lkml.kernel.org/r/20230926120905.392903-1-bhe@redhat.com Fixes: 247262756121 ("crash: add generic infrastructure for crash hotplug support") Signed-off-by: Baoquan He bhe@redhat.com Tested-by: Eric DeVolder eric.devolder@oracle.com Reviewed-by: Eric DeVolder eric.devolder@oracle.com Reviewed-by: Valentin Schneider vschneid@redhat.com Cc: Sourabh Jain sourabhjain@linux.ibm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

kernel/crash_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)

--- a/kernel/crash_core.c~crash-add-lock-to-serialize-crash-hotplug-handling +++ a/kernel/crash_core.c @@ -740,6 +740,17 @@ subsys_initcall(crash_notes_memory_init) #define pr_fmt(fmt) "crash hp: " fmt

/* + * Different than kexec/kdump loading/unloading/jumping/shrinking which + * usually rarely happen, there will be many crash hotplug events notified + * during one short period, e.g one memory board is hot added and memory + * regions are online. So mutex lock __crash_hotplug_lock is used to + * serialize the crash hotplug handling specifically. + */ +DEFINE_MUTEX(__crash_hotplug_lock); +#define crash_hotplug_lock() mutex_lock(&__crash_hotplug_lock) +#define crash_hotplug_unlock() mutex_unlock(&__crash_hotplug_lock) + +/* * This routine utilized when the crash_hotplug sysfs node is read. * It reflects the kernel's ability/permission to update the crash * elfcorehdr directly. @@ -748,9 +759,11 @@ int crash_check_update_elfcorehdr(void) { int rc = 0;

+ crash_hotplug_lock(); /* Obtain lock while reading crash information */ if (!kexec_trylock()) { pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n"); + crash_hotplug_unlock(); return 0; } if (kexec_crash_image) { @@ -761,6 +774,7 @@ int crash_check_update_elfcorehdr(void) } /* Release lock now that update complete */ kexec_unlock(); + crash_hotplug_unlock();

return rc; } @@ -783,9 +797,11 @@ static void crash_handle_hotplug_event(u { struct kimage *image;

+ crash_hotplug_lock(); /* Obtain lock while changing crash information */ if (!kexec_trylock()) { pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n"); + crash_hotplug_unlock(); return; }

@@ -852,6 +868,7 @@ static void crash_handle_hotplug_event(u out: /* Release lock now that update complete */ kexec_unlock(); + crash_hotplug_unlock(); }

static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v) _

Patches currently in -mm which might be from bhe@redhat.com are

crash_corec-remove-unnecessary-parameter-of-function.patch crash_core-change-the-prototype-of-function-parse_crashkernel.patch crash_core-change-parse_crashkernel-to-support-crashkernel=highlow-parsing.patch crash_core-add-generic-function-to-do-reservation.patch crash_core-move-crashk_res-definition-into-crash_corec.patch x86-kdump-use-generic-interface-to-simplify-crashkernel-reservation-code.patch x86-kdump-use-generic-interface-to-simplify-crashkernel-reservation-code-fix.patch arm64-kdump-use-generic-interface-to-simplify-crashkernel-reservation.patch riscv-kdump-use-generic-interface-to-simplify-crashkernel-reservation.patch crash_corec-remove-unneeded-functions.patch