panic: Make panic_timeout configurable

The panic_timeout value can be set via the command line option
'panic=x', or via /proc/sys/kernel/panic, however that is not
sufficient when the panic occurs before we are able to set up
these values. Thus, add a CONFIG_PANIC_TIMEOUT so that we can
set the desired value from the .config.

The default panic_timeout value continues to be 0 - wait
forever. Also adds set_arch_panic_timeout(new_timeout,
arch_default_timeout), which is intended to be used by arches in
arch_setup(). The idea being that the new_timeout is only set if
the user hasn't changed from the arch_default_timeout.

Signed-off-by: Jason Baron <jbaron@akamai.com>
Cc: benh@kernel.crashing.org
Cc: paulus@samba.org
Cc: ralf@linux-mips.org
Cc: mpe@ellerman.id.au
Cc: felipe.contreras@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1a1674daec27c534df409697025ac568ebcee91e.1385418410.git.jbaron@akamai.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 19 insertions, 1 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d4e98d13eff4..2ac02772a86e 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -393,6 +393,15 @@ extern int panic_on_oops;
 extern int panic_on_unrecovered_nmi;
 extern int panic_on_io_nmi;
 extern int sysctl_panic_on_stackoverflow;
+/*
+ * Only to be used by arch init code. If the user over-wrote the default
+ * CONFIG_PANIC_TIMEOUT, honor it.
+ */
+static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
+{
+        if (panic_timeout == arch_default_timeout)
+                panic_timeout = timeout;
+}
 extern const char *print_tainted(void);
 enum lockdep_ok {
         LOCKDEP_STILL_OK,
diff --git a/kernel/panic.c b/kernel/panic.c
index c00b4ceb39e8..6d6300375090 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -33,7 +33,7 @@ static int pause_on_oops;
 static int pause_on_oops_flag;
 static DEFINE_SPINLOCK(pause_on_oops_lock);
 
-int panic_timeout;
+int panic_timeout = CONFIG_PANIC_TIMEOUT;
 EXPORT_SYMBOL_GPL(panic_timeout);
 
 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index db25707aa41b..6982094a7e74 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -761,6 +761,15 @@ config PANIC_ON_OOPS_VALUE
         default 0 if !PANIC_ON_OOPS
         default 1 if PANIC_ON_OOPS
 
+config PANIC_TIMEOUT
+        int "panic timeout"
+        default 0
+        help
+          Set the timeout value (in seconds) until a reboot occurs when the
+          the kernel panics. If n = 0, then we wait forever. A timeout
+          value n > 0 will wait n seconds before rebooting, while a timeout
+          value n < 0 will reboot immediately.
+
 config SCHED_DEBUG
         bool "Collect scheduler debugging info"
         depends on DEBUG_KERNEL && PROC_FS