panic: panic=-1 for immediate reboot

When a kernel BUG or oops occurs, ChromeOS intends to panic and
immediately reboot, with stacktrace and other messages preserved in RAM
across reboot.

But the longer we delay, the more likely the user is to poweroff and
lose the info.

panic_timeout (seconds before rebooting) is set by panic= boot option or
sysctl or /proc/sys/kernel/panic; but 0 means wait forever, so at
present we have to delay at least 1 second.

Let a negative number mean reboot immediately (with the small cosmetic
benefit of suppressing that newline-less "Rebooting in %d seconds.."
message).

Signed-off-by: Hugh Dickins <hughd@chromium.org>
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Olaf Hering <olaf@aepfle.de>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
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 a70e43edcb65c9d732d3877499410b487911d213..4ca93898fbd3d984a3bccf550b5281d3f0a90e56 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1846,7 +1846,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        See Documentation/sound/oss/oss-parameters.txt
 
        panic=          [KNL] Kernel behaviour on panic: delay <timeout>
-                       seconds before rebooting
+                       timeout > 0: seconds before rebooting
+                       timeout = 0: wait forever
+                       timeout < 0: reboot immediately
                        Format: <timeout>
 
        parkbd.port=    [HW] Parallel port number the keyboard adapter is

diff --git a/kernel/panic.c b/kernel/panic.c
index 69231670eb952357809488fa58cffef5596e9c63..d7bb6974efb56b6070a6c9067bd87ba55a7273da 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -119,6 +119,8 @@ NORET_TYPE void panic(const char * fmt, ...)
                        }
                        mdelay(PANIC_TIMER_STEP);
                }
+       }
+       if (panic_timeout != 0) {
                /*
                 * This will not be a clean reboot, with everything
                 * shutting down.  But if there is a chance of