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panic: fix the panic_print NMI backtrace setting

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Commit 8d470a45d1 ("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: 8d470a45d1 ("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>
This commit is contained in:
Guilherme G. Piccoli 2023-02-26 13:08:38 -03:00 committed by Andrew Morton
parent 359d62559f
commit b905039e42
1 changed files with 26 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
kernel/panic.c
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@ -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