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authorGuilherme G. Piccoli <gpiccoli@igalia.com>2023-02-26 13:08:38 -0300
committerAndrew Morton <akpm@linux-foundation.org>2023-03-02 21:54:23 -0800
commitb905039e428d639adeebb719b76f98865ea38d4d (patch)
tree2c3318a1aa7bad662f702c8a2af43f35ea9da33b /kernel
parent359d62559f578dc1ac86fd2d198f1455e9d8ce04 (diff)
downloadlwn-b905039e428d639adeebb719b76f98865ea38d4d.tar.gz
lwn-b905039e428d639adeebb719b76f98865ea38d4d.zip
panic: fix the panic_print NMI backtrace setting
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@igalia.com Fixes: 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print") Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Cc: <stable@vger.kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Feng Tang <feng.tang@intel.com> Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: Kees Cook <keescook@chromium.org> Cc: Michael Kelley <mikelley@microsoft.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/panic.c44
1 files changed, 26 insertions, 18 deletions
diff --git a/kernel/panic.c b/kernel/panic.c
index 487f5b03bf83..5cfea8302d23 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -212,9 +212,6 @@ static void panic_print_sys_info(bool console_flush)
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 *origin)
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