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From: Jason Wessel on 12 Feb 2010 17:40
It is highly desirable to trap into kdb on panic, and in order
to do so the notifier must be called before smp_send_stop(),
else the debug_core will not be able to correctly trap
all the CPUs.

CC: Ingo Molnar <mingo(a)elte.hu>
CC: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Jason Wessel <jason.wessel(a)windriver.com>
---
kernel/debug/debug_core.c | 18 ++++++++++++++++++
kernel/panic.c | 7 ++++---
2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index bfdba97..580fc3b 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -754,11 +754,27 @@ static struct sysrq_key_op sysrq_dbg_op = {
};
#endif

+static int kgdb_panic_event(struct notifier_block *self,
+ unsigned long val,
+ void *data)
+{
+ if (dbg_kdb_mode)
+ kdb_printf("PANIC: %s\n", (char *)data);
+ kgdb_breakpoint();
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block kgdb_panic_event_nb = {
+ .notifier_call = kgdb_panic_event,
+};
+
static void kgdb_register_callbacks(void)
{
if (!kgdb_io_module_registered) {
kgdb_io_module_registered = 1;
kgdb_arch_init();
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &kgdb_panic_event_nb);
#ifdef CONFIG_MAGIC_SYSRQ
register_sysrq_key('g', &sysrq_dbg_op);
#endif
@@ -778,6 +794,8 @@ static void kgdb_unregister_callbacks(void)
*/
if (kgdb_io_module_registered) {
kgdb_io_module_registered = 0;
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ &kgdb_panic_event_nb);
kgdb_arch_exit();
#ifdef CONFIG_MAGIC_SYSRQ
unregister_sysrq_key('g', &sysrq_dbg_op);
diff --git a/kernel/panic.c b/kernel/panic.c
index c787333..428d15b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -66,10 +66,13 @@ NORET_TYPE void panic(const char * fmt, ...)
*/
preempt_disable();

- bust_spinlocks(1);
va_start(args, fmt);
vsnprintf(buf, sizeof(buf), fmt, args);
va_end(args);
+
+ atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
+
+ bust_spinlocks(1);
printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
#ifdef CONFIG_DEBUG_BUGVERBOSE
dump_stack();
@@ -91,8 +94,6 @@ NORET_TYPE void panic(const char * fmt, ...)
*/
smp_send_stop();

- atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
-
bust_spinlocks(0);

if (!panic_blink)
--
1.6.4.rc1

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Prev: [PATCH 04/28] kgdb,sparc: Add in kgdb_arch_set_pc for sparc
Next: [PATCH 21/28] kgdboc,kdb: Allow kdb to work on a non open console port