[PATCH v2] reboot: Add timeout for device shutdown

[Soumya Khasnis]

The device shutdown callbacks invoked during shutdown/reboot
are prone to errors depending on the device state or mishandling
by one or more driver. In order to prevent a device hang in such
scenarios, we bail out after a timeout while dumping a meaningful
call trace of the shutdown callback which blocks the shutdown or
reboot process.

Signed-off-by: Soumya Khasnis <soumya.khasnis@xxxxxxxx>
Signed-off-by: Srinavasa Nagaraju <Srinavasa.Nagaraju@xxxxxxxx>
---
 drivers/base/Kconfig | 15 +++++++++++++++
 kernel/reboot.c      | 46 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 2b8fd6bb7da0..d06e379b6281 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -243,3 +243,18 @@ config FW_DEVLINK_SYNC_STATE_TIMEOUT
 	  work on.
 
 endmenu
+
+config DEVICE_SHUTDOWN_TIMEOUT
+	bool "device shutdown timeout"
+	default n
+	help
+	   Enable timeout for device shutdown. Helps in case device shutdown
+	   is hung during shoutdonw and reboot.
+
+
+config DEVICE_SHUTDOWN_TIMEOUT_SEC
+	int "device shutdown timeout in seconds"
+	default 5
+	depends on DEVICE_SHUTDOWN_TIMEOUT
+	help
+	  sets time for device shutdown timeout in seconds
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 22c16e2564cc..8460bd24563b 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -18,7 +18,7 @@
 #include <linux/syscalls.h>
 #include <linux/syscore_ops.h>
 #include <linux/uaccess.h>
-
+#include <linux/sched/debug.h>
 /*
  * this indicates whether you can reboot with ctrl-alt-del: the default is yes
  */
@@ -48,6 +48,14 @@ int reboot_cpu;
 enum reboot_type reboot_type = BOOT_ACPI;
 int reboot_force;
 
+#ifdef CONFIG_DEVICE_SHUTDOWN_TIMEOUT
+struct device_shutdown_timeout {
+	struct timer_list timer;
+	struct task_struct *task;
+} devs_shutdown;
+#define SHUTDOWN_TIMEOUT CONFIG_DEVICE_SHUTDOWN_TIMEOUT_SEC
+#endif
+
 struct sys_off_handler {
 	struct notifier_block nb;
 	int (*sys_off_cb)(struct sys_off_data *data);
@@ -88,12 +96,46 @@ void emergency_restart(void)
 }
 EXPORT_SYMBOL_GPL(emergency_restart);
 
+#ifdef CONFIG_DEVICE_SHUTDOWN_TIMEOUT
+static void device_shutdown_timeout_handler(struct timer_list *t)
+{
+	pr_emerg("**** device shutdown timeout ****\n");
+	show_stack(devs_shutdown.task, NULL, KERN_EMERG);
+	if (system_state == SYSTEM_RESTART)
+		emergency_restart();
+	else
+		machine_power_off();
+}
+
+static void device_shutdown_timer_set(void)
+{
+	devs_shutdown.task = current;
+	timer_setup(&devs_shutdown.timer, device_shutdown_timeout_handler, 0);
+	devs_shutdown.timer.expires = jiffies + SHUTDOWN_TIMEOUT * HZ;
+	add_timer(&devs_shutdown.timer);
+}
+
+static void device_shutdown_timer_clr(void)
+{
+	del_timer(&devs_shutdown.timer);
+}
+#else
+static inline void device_shutdown_timer_set(void)
+{
+}
+static inline void device_shutdown_timer_clr(void)
+{
+}
+#endif
+
 void kernel_restart_prepare(char *cmd)
 {
 	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
 	system_state = SYSTEM_RESTART;
 	usermodehelper_disable();
+	device_shutdown_timer_set();
 	device_shutdown();
+	device_shutdown_timer_clr();
 }
 
 /**
@@ -293,7 +335,9 @@ static void kernel_shutdown_prepare(enum system_states state)
 		(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
 	system_state = state;
 	usermodehelper_disable();
+	device_shutdown_timer_set();
 	device_shutdown();
+	device_shutdown_timer_clr();
 }
 /**
  *	kernel_halt - halt the system
-- 
2.40.0