Commit b905039e authored by Guilherme G. Piccoli's avatar Guilherme G. Piccoli Committed by Andrew Morton
Browse files

panic: fix the panic_print NMI backtrace setting 

Commit 8d470a45 ("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: 8d470a45 ("panic: add option to dump all CPUs backtraces in panic_print")
Signed-off-by: default avatarGuilherme 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 359d6255

kernel/panic.c

+26 −18
Original line number Diff line number Diff line
@@ -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