The quilt patch titled
Subject: panic: fix the panic_print NMI backtrace setting
has been removed from the -mm tree. Its filename was
panic-fixes-the-panic_print-nmi-backtrace-setting.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: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>
Subject: panic: fix the panic_print NMI backtrace setting
Date: Sun, 26 Feb 2023 13:08:38 -0300
Commit 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in
panic_print") introduced a setting for the "panic_print" kernel parameter
to allow users to request a NMI backtrace on panic. Problem is that the
panic_print handling happens after the secondary CPUs are already
disabled, hence this option ended-up being kind of a no-op - kernel skips
the NMI trace in idling CPUs, which is the case of offline CPUs.
Fix it by checking the NMI backtrace bit in the panic_print prior to the
CPU disabling function.
Link: https://lkml.kernel.org/r/20230226160838.414257-1-gpiccoli@xxxxxxxxxx
Fixes: 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print")
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Feng Tang <feng.tang@xxxxxxxxx>
Cc: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/kernel/panic.c~panic-fixes-the-panic_print-nmi-backtrace-setting
+++ a/kernel/panic.c
@@ -212,9 +212,6 @@ static void panic_print_sys_info(bool co
return;
}
- if (panic_print & PANIC_PRINT_ALL_CPU_BT)
- trigger_all_cpu_backtrace();
-
if (panic_print & PANIC_PRINT_TASK_INFO)
show_state();
@@ -244,6 +241,30 @@ void check_panic_on_warn(const char *ori
origin, limit);
}
+/*
+ * Helper that triggers the NMI backtrace (if set in panic_print)
+ * and then performs the secondary CPUs shutdown - we cannot have
+ * the NMI backtrace after the CPUs are off!
+ */
+static void panic_other_cpus_shutdown(bool crash_kexec)
+{
+ if (panic_print & PANIC_PRINT_ALL_CPU_BT)
+ trigger_all_cpu_backtrace();
+
+ /*
+ * Note that smp_send_stop() is the usual SMP shutdown function,
+ * which unfortunately may not be hardened to work in a panic
+ * situation. If we want to do crash dump after notifier calls
+ * and kmsg_dump, we will need architecture dependent extra
+ * bits in addition to stopping other CPUs, hence we rely on
+ * crash_smp_send_stop() for that.
+ */
+ if (!crash_kexec)
+ smp_send_stop();
+ else
+ crash_smp_send_stop();
+}
+
/**
* panic - halt the system
* @fmt: The text string to print
@@ -334,23 +355,10 @@ void panic(const char *fmt, ...)
*
* Bypass the panic_cpu check and call __crash_kexec directly.
*/
- if (!_crash_kexec_post_notifiers) {
+ if (!_crash_kexec_post_notifiers)
__crash_kexec(NULL);
- /*
- * Note smp_send_stop is the usual smp shutdown function, which
- * unfortunately means it may not be hardened to work in a
- * panic situation.
- */
- smp_send_stop();
- } else {
- /*
- * If we want to do crash dump after notifier calls and
- * kmsg_dump, we will need architecture dependent extra
- * works in addition to stopping other CPUs.
- */
- crash_smp_send_stop();
- }
+ panic_other_cpus_shutdown(_crash_kexec_post_notifiers);
/*
* Run any panic handlers, including those that might need to
_
Patches currently in -mm which might be from gpiccoli@xxxxxxxxxx are
