[PATCH v3 2/3] s390: Implement arch_do_panic

[Mete Durlu]

s390 has a custom panic handler which carries out user specified actions
during a panic scenario. This handler is invoked via the panic_notifier
call chain and executed before panic_timeout value is evaluated in
common code.

Use arch_do_panic() hook to invoke arch specific panic handling instead
of using panic_notifier call chain. By reordering s390's panic handler
allow more information to be printed during a panic.
The execution order of panic handlers now allows for user specified
panic_timeout value to be taken into account. This fixes the broken
"panic" kernel parameter for s390, earlier it was just ignored
inexplicibly.

This now means that the panic_timeout value takes precedence over user
defined on_panic behavior defined via "chshut" or writing to
/sys/firmware/shutdown_actions/on_panic.

Fixes: ff6b8ea68f4b ("[S390] ipl/dump on panic.")
Suggested-by: Sven Schnelle <svens@xxxxxxxxxxxxx>
Signed-off-by: Mete Durlu <meted@xxxxxxxxxxxxx>
---
 arch/s390/kernel/ipl.c | 19 +++++--------------
 kernel/panic.c         |  3 ---
 2 files changed, 5 insertions(+), 17 deletions(-)

diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
index 3c346b02ceb9..6a5fa9213450 100644
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -2111,11 +2111,15 @@ static ssize_t on_panic_store(struct kobject *kobj,
 			      struct kobj_attribute *attr,
 			      const char *buf, size_t len)
 {
+	if (panic_timeout) {
+		pr_warn("on_panic action will be ignored in favor of panic timeout (panic=%d)",
+			panic_timeout);
+	}
 	return set_trigger(buf, &on_panic_trigger, len);
 }
 static struct kobj_attribute on_panic_attr = __ATTR_RW(on_panic);
 
-static void do_panic(void)
+void arch_do_panic(void)
 {
 	lgr_info_log();
 	on_panic_trigger.action->fn(&on_panic_trigger);
@@ -2331,18 +2335,6 @@ static int __init vmcmd_on_poff_setup(char *str)
 }
 __setup("vmpoff=", vmcmd_on_poff_setup);
 
-static int on_panic_notify(struct notifier_block *self,
-			   unsigned long event, void *data)
-{
-	do_panic();
-	return NOTIFY_OK;
-}
-
-static struct notifier_block on_panic_nb = {
-	.notifier_call = on_panic_notify,
-	.priority = INT_MIN,
-};
-
 void __init setup_ipl(void)
 {
 	BUILD_BUG_ON(sizeof(struct ipl_parameter_block) != PAGE_SIZE);
@@ -2375,7 +2367,6 @@ void __init setup_ipl(void)
 		/* We have no info to copy */
 		break;
 	}
-	atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
 }
 
 void __no_stack_protector s390_reset_system(void)
diff --git a/kernel/panic.c b/kernel/panic.c
index 726a97842232..ee6e3f9e3900 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -752,9 +752,6 @@ void vpanic(const char *fmt, va_list args)
 		pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
 			 "twice on console to return to the boot prom\n");
 	}
-#endif
-#if defined(CONFIG_S390)
-	disabled_wait();
 #endif
 	pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
 

-- 
2.53.0