Merge branch 'mm-nonmm-stable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

1 files changed, 48 insertions, 54 deletions

diff --git a/kernel/panic.c b/kernel/panic.c
index 213725b612aa..170744163fc2 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -307,7 +307,7 @@ atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
 atomic_t panic_redirect_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
 
 #if defined(CONFIG_SMP) && defined(CONFIG_CRASH_DUMP)
-static char *panic_force_buf;
+static char panic_force_buf[PANIC_MSG_BUFSZ];
 
 static int __init panic_force_cpu_setup(char *str)
 {
@@ -326,17 +326,6 @@ static int __init panic_force_cpu_setup(char *str)
 }
 early_param("panic_force_cpu", panic_force_cpu_setup);
 
-static int __init panic_force_cpu_late_init(void)
-{
-	if (panic_force_cpu < 0)
-		return 0;
-
-	panic_force_buf = kmalloc(PANIC_MSG_BUFSZ, GFP_KERNEL);
-
-	return 0;
-}
-late_initcall(panic_force_cpu_late_init);
-
 static void do_panic_on_target_cpu(void *info)
 {
 	panic("%s", (char *)info);
@@ -371,15 +360,16 @@ int __weak panic_smp_redirect_cpu(int target_cpu, void *msg)
  * for the crash kernel to function correctly. This function redirects
  * panic handling to the CPU specified via the panic_force_cpu= boot parameter.
  *
- * Returns false if panic should proceed on current CPU.
- * Returns true if panic was redirected.
+ * Returns true when this CPU must stop: the panic was redirected or is
+ * already running on another CPU.
+ * Returns false when panic() should proceed on this CPU.
  */
 __printf(1, 0)
 static bool panic_try_force_cpu(const char *fmt, va_list args)
 {
 	int this_cpu = raw_smp_processor_id();
 	int old_cpu = PANIC_CPU_INVALID;
-	const char *msg;
+	va_list ap;
 
 	/* Feature not enabled via boot parameter */
 	if (panic_force_cpu < 0)
@@ -396,27 +386,27 @@ static bool panic_try_force_cpu(const char *fmt, va_list args)
 		return false;
 	}
 
-	/* Another panic already in progress */
+	/*
+	 * Don't redirect when a panic is already in progress. Stop this
+	 * CPU when it's another one, proceed when it's this one.
+	 */
 	if (panic_in_progress())
-		return false;
+		return panic_on_other_cpu();
 
 	/*
-	 * Only one CPU can do the redirect. Use atomic cmpxchg to ensure
-	 * we don't race with another CPU also trying to redirect.
+	 * Only one CPU can do the redirection. Others should go offline.
+	 * Continue with panic() when we already tried the redirection
+	 * from this CPU before, for example via nmi_panic().
 	 */
 	if (!atomic_try_cmpxchg(&panic_redirect_cpu, &old_cpu, this_cpu))
-		return false;
+		return old_cpu != this_cpu;
 
 	/*
-	 * Use dynamically allocated buffer if available, otherwise
-	 * fall back to static message for early boot panics or allocation failure.
+	 * Do not consume args, the caller reuses them if we fail.
 	 */
-	if (panic_force_buf) {
-		vsnprintf(panic_force_buf, PANIC_MSG_BUFSZ, fmt, args);
-		msg = panic_force_buf;
-	} else {
-		msg = "Redirected panic (buffer unavailable)";
-	}
+	va_copy(ap, args);
+	vsnprintf(panic_force_buf, PANIC_MSG_BUFSZ, fmt, ap);
+	va_end(ap);
 
 	console_verbose();
 	bust_spinlocks(1);
@@ -431,7 +421,7 @@ static bool panic_try_force_cpu(const char *fmt, va_list args)
 		dump_stack();
 	}
 
-	if (panic_smp_redirect_cpu(panic_force_cpu, (void *)msg) != 0) {
+	if (panic_smp_redirect_cpu(panic_force_cpu, panic_force_buf) != 0) {
 		atomic_set(&panic_redirect_cpu, PANIC_CPU_INVALID);
 		pr_warn("panic: failed to redirect to CPU %d, continuing on CPU %d\n",
 			panic_force_cpu, this_cpu);
@@ -503,17 +493,35 @@ bool panic_on_other_cpu(void)
 EXPORT_SYMBOL(panic_on_other_cpu);
 
 /*
- * A variant of panic() called from NMI context. We return if we've already
- * panicked on this CPU. If another CPU already panicked, loop in
- * nmi_panic_self_stop() which can provide architecture dependent code such
- * as saving register state for crash dump.
+ * A variant of panic() called from NMI context. The panic is first
+ * redirected to the CPU requested via panic_force_cpu=, when configured.
+ * We return if we've already panicked on this CPU. If another CPU already
+ * panicked, loop in nmi_panic_self_stop() which can provide architecture
+ * dependent code for saving register state for crash dump.
  */
-void nmi_panic(struct pt_regs *regs, const char *msg)
+void nmi_panic(struct pt_regs *regs, const char *fmt, ...)
 {
+	va_list args;
+
+	va_start(args, fmt);
+
+	/* Try to redirect to the requested CPU before claiming panic_cpu. */
+	if (panic_try_force_cpu(fmt, args)) {
+		/*
+		 * Mark ourselves offline so panic_other_cpus_shutdown() won't
+		 * wait for us on architectures that check num_online_cpus().
+		 */
+		set_cpu_online(raw_smp_processor_id(), false);
+		nmi_panic_self_stop(regs);
+	}
+
 	if (panic_try_start())
-		panic("%s", msg);
-	else if (panic_on_other_cpu())
+		vpanic(fmt, args);
+
+	if (panic_on_other_cpu())
 		nmi_panic_self_stop(regs);
+
+	va_end(args);
 }
 EXPORT_SYMBOL(nmi_panic);
 
@@ -567,6 +575,8 @@ static void panic_other_cpus_shutdown(bool crash_kexec)
 		crash_smp_send_stop();
 }
 
+void __weak arch_do_panic(void) {}
+
 /**
  * vpanic - halt the system
  * @fmt: The text string to print
@@ -742,20 +752,9 @@ void vpanic(const char *fmt, va_list args)
 			reboot_mode = panic_reboot_mode;
 		emergency_restart();
 	}
-#ifdef __sparc__
-	{
-		extern int stop_a_enabled;
-		/* Make sure the user can actually press Stop-A (L1-A) */
-		stop_a_enabled = 1;
-		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);
 
+	arch_do_panic();
 	/* Do not scroll important messages printed above */
 	suppress_printk = 1;
 
@@ -1225,14 +1224,9 @@ static int panic_print_set(const char *val, const struct kernel_param *kp)
 	return  param_set_ulong(val, kp);
 }
 
-static int panic_print_get(char *val, const struct kernel_param *kp)
-{
-	return  param_get_ulong(val, kp);
-}
-
 static const struct kernel_param_ops panic_print_ops = {
 	.set	= panic_print_set,
-	.get	= panic_print_get,
+	.get	= param_get_ulong,
 };
 __core_param_cb(panic_print, &panic_print_ops, &panic_print, 0644);