kernel/panic.c: add "crash_kexec_post_notifiers" option for kdump after panic_notifers

Add a "crash_kexec_post_notifiers" boot option to run kdump after
running panic_notifiers and dump kmsg.  This can help rare situations
where kdump fails because of unstable crashed kernel or hardware failure
(memory corruption on critical data/code), or the 2nd kernel is already
broken by the 1st kernel (it's a broken behavior, but who can guarantee
that the "crashed" kernel works correctly?).

Usage: add "crash_kexec_post_notifiers" to kernel boot option.

Note that this actually increases risks of the failure of kdump.  This
option should be set only if you worry about the rare case of kdump
failure rather than increasing the chance of success.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Motohiro Kosaki <Motohiro.Kosaki@us.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Satoru MORIYA <satoru.moriya.br@hitachi.com>
Cc: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9973a7e2e0ac5a1ff7e55f38c7b724d52c60cc3e..b9f67781c577d04118de98dee652baa32568618b 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2361,6 +2361,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        timeout < 0: reboot immediately
                        Format: <timeout>
 
+       crash_kexec_post_notifiers
+                       Run kdump after running panic-notifiers and dumping
+                       kmsg. This only for the users who doubt kdump always
+                       succeeds in any situation.
+                       Note that this also increases risks of kdump failure,
+                       because some panic notifiers can make the crashed
+                       kernel more unstable.
+
        parkbd.port=    [HW] Parallel port number the keyboard adapter is
                        connected to, default is 0.
                        Format: <parport#>

diff --git a/kernel/panic.c b/kernel/panic.c
index d02fa9fef46ae14c218826e4c5e271ac8894aa51..62e16cef9cc23e848f524ed650617741d69069bd 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -32,6 +32,7 @@ static unsigned long tainted_mask;
 static int pause_on_oops;
 static int pause_on_oops_flag;
 static DEFINE_SPINLOCK(pause_on_oops_lock);
+static bool crash_kexec_post_notifiers;
 
 int panic_timeout = CONFIG_PANIC_TIMEOUT;
 EXPORT_SYMBOL_GPL(panic_timeout);
@@ -112,9 +113,11 @@ void panic(const char *fmt, ...)
        /*
         * If we have crashed and we have a crash kernel loaded let it handle
         * everything else.
-        * Do we want to call this before we try to display a message?
+        * If we want to run this after calling panic_notifiers, pass
+        * the "crash_kexec_post_notifiers" option to the kernel.
         */
-       crash_kexec(NULL);
+       if (!crash_kexec_post_notifiers)
+               crash_kexec(NULL);
 
        /*
         * Note smp_send_stop is the usual smp shutdown function, which
@@ -131,6 +134,15 @@ void panic(const char *fmt, ...)
 
        kmsg_dump(KMSG_DUMP_PANIC);
 
+       /*
+        * If you doubt kdump always works fine in any situation,
+        * "crash_kexec_post_notifiers" offers you a chance to run
+        * panic_notifiers and dumping kmsg before kdump.
+        * Note: since some panic_notifiers can make crashed kernel
+        * more unstable, it can increase risks of the kdump failure too.
+        */
+       crash_kexec(NULL);
+
        bust_spinlocks(0);
 
        if (!panic_blink)
@@ -472,6 +484,13 @@ EXPORT_SYMBOL(__stack_chk_fail);
 core_param(panic, panic_timeout, int, 0644);
 core_param(pause_on_oops, pause_on_oops, int, 0644);
 
+static int __init setup_crash_kexec_post_notifiers(char *s)
+{
+       crash_kexec_post_notifiers = true;
+       return 0;
+}
+early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers);
+
 static int __init oops_setup(char *s)
 {
        if (!s)