On Tue, Jul 7, 2020 at 12:04 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On Wed, Jul 01, 2020 at 07:03:40PM +0800, Woody Lin wrote:
> > Add module parameters 'soft_reboot_cmd' and 'soft_active_on_boot' for
> > customizing softdog configuration; config reboot command by assigning
> > soft_reboot_cmd, and set soft_active_on_boot to start up softdog
> > timer at module initialization stage.
> >
> > Signed-off-by: Woody Lin <woodylin@xxxxxxxxxx>
> > ---
> > drivers/watchdog/softdog.c | 56 ++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 56 insertions(+)
> >
> > diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c
> > index 3e4885c1545e..8c8d214b6aa7 100644
> > --- a/drivers/watchdog/softdog.c
> > +++ b/drivers/watchdog/softdog.c
> > @@ -20,11 +20,13 @@
> > #include <linux/hrtimer.h>
> > #include <linux/init.h>
> > #include <linux/kernel.h>
> > +#include <linux/kthread.h>
> > #include <linux/module.h>
> > #include <linux/moduleparam.h>
> > #include <linux/reboot.h>
> > #include <linux/types.h>
> > #include <linux/watchdog.h>
> > +#include <linux/workqueue.h>
> >
> > #define TIMER_MARGIN 60 /* Default is 60 seconds */
> > static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
> > @@ -49,11 +51,33 @@ module_param(soft_panic, int, 0);
> > MODULE_PARM_DESC(soft_panic,
> > "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
> >
> > +static char *soft_reboot_cmd;
> > +module_param(soft_reboot_cmd, charp, 0000);
> > +MODULE_PARM_DESC(soft_reboot_cmd,
> > + "Set reboot command. Emergency reboot takes place if unset");
> > +
> > +static bool soft_active_on_boot;
> > +module_param(soft_active_on_boot, bool, 0000);
> > +MODULE_PARM_DESC(soft_active_on_boot,
> > + "Set to true to active Softdog on boot (default=false)");
> > +
> > static struct hrtimer softdog_ticktock;
> > static struct hrtimer softdog_preticktock;
> >
> > +static int reboot_kthread_fn(void *data)
> > +{
> > + kernel_restart(soft_reboot_cmd);
> > + return -EPERM; /* Should not reach here */
> > +}
> > +
> > +static void reboot_work_fn(struct work_struct *unused)
> > +{
> > + kthread_run(reboot_kthread_fn, NULL, "softdog_reboot");
> > +}
> > +
> > static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
> > {
> > + static bool soft_reboot_fired;
>
> Per coding style there should be an empty line here.
Ack.
>
> > module_put(THIS_MODULE);
> > if (soft_noboot) {
> > pr_crit("Triggered - Reboot ignored\n");
> > @@ -62,6 +86,33 @@ static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
> > panic("Software Watchdog Timer expired");
> > } else {
> > pr_crit("Initiating system reboot\n");
> > + if (!soft_reboot_fired && soft_reboot_cmd != NULL) {
> > + static DECLARE_WORK(reboot_work, reboot_work_fn);
> > + /*
> > + * The 'kernel_restart' is a 'might-sleep' operation.
> > + * Also, executing it in system-wide workqueues blocks
> > + * any driver from using the same workqueue in its
> > + * shutdown callback function. Thus, we should execute
> > + * the 'kernel_restart' in a standalone kernel thread.
> > + * But since starting a kernel thread is also a
> > + * 'might-sleep' operation, so the 'reboot_work' is
> > + * required as a launcher of the kernel thread.
> > + *
> > + * After request the reboot, restart the timer to
> > + * schedule an 'emergency_restart' reboot after
> > + * 'TIMER_MARGIN' seconds. It's because if the softdog
> > + * hangs, it might be because of scheduling issues. And
> > + * if that is the case, both 'schedule_work' and
> > + * 'kernel_restart' may possibly be malfunctional at the
> > + * same time.
> > + */
> > + soft_reboot_fired = true;
> > + schedule_work(&reboot_work);
> > + hrtimer_add_expires_ns(timer,
> > + (u64)TIMER_MARGIN * NSEC_PER_SEC);
> > +
> > + return HRTIMER_RESTART;
> > + }
> > emergency_restart();
> > pr_crit("Reboot didn't ?????\n");
> > }
> > @@ -145,12 +196,17 @@ static int __init softdog_init(void)
> > softdog_preticktock.function = softdog_pretimeout;
> > }
> >
> > + if (soft_active_on_boot)
> > + softdog_ping(&softdog_dev);
> > +
> > ret = watchdog_register_device(&softdog_dev);
> > if (ret)
> > return ret;
> >
> > pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
> > soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
> > + pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n",
> > + soft_reboot_cmd, soft_active_on_boot);
>
> soft_reboot_cmd can be NULL, which makes the output a bit awkward.
Then how about change it to something like this:
"soft_reboot_cmd=%s", soft_reboot_cmd ?: "<null> (emergency reboot)"
Then we will see "soft_reboot_cmd=<null> (emergency reboot)" when it's NULL.
>
> >
> > return 0;
> > }
Woody
