ARM: add option to flush console before reboot

If the console_lock was held while the system was rebooted, the messages
in the temporary logbuffer would not have propogated to all the console
drivers.

This force releases the console lock if it failed to be acquired.

Change-Id: I193dcf7b968be17966833e50b8b8bc70d5d9fe89
Signed-off-by: Dima Zavin <dima@android.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index b18bd2f91d6..185f5b7e694 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -32,6 +32,7 @@
 #include <linux/hw_breakpoint.h>
 #include <linux/cpuidle.h>
 #include <linux/leds.h>
+#include <linux/console.h>
 
 #include <asm/cacheflush.h>
 #include <asm/idmap.h>
@@ -60,6 +61,31 @@ static const char *isa_modes[] = {
 extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
 typedef void (*phys_reset_t)(unsigned long);
 
+#ifdef CONFIG_ARM_FLUSH_CONSOLE_ON_RESTART
+void arm_machine_flush_console(void)
+{
+	printk("\n");
+	pr_emerg("Restarting %s\n", linux_banner);
+	if (console_trylock()) {
+		console_unlock();
+		return;
+	}
+
+	mdelay(50);
+
+	local_irq_disable();
+	if (!console_trylock())
+		pr_emerg("arm_restart: Console was locked! Busting\n");
+	else
+		pr_emerg("arm_restart: Console was locked!\n");
+	console_unlock();
+}
+#else
+void arm_machine_flush_console(void)
+{
+}
+#endif
+
 /*
  * A temporary stack to use for CPU reset. This is static so that we
  * don't clobber it with the identity mapping. When running with this
@@ -240,6 +266,10 @@ void machine_restart(char *cmd)
 {
 	smp_send_stop();
 
+	/* Flush the console to make sure all the relevant messages make it
+	 * out to the console drivers */
+	arm_machine_flush_console();
+
 	arm_pm_restart(reboot_mode, cmd);
 
 	/* Give a grace period for failure to restart of 1s */