On Wed, Jul 01, 2020 at 10:32:16PM +0800, Woody Lin wrote:
> Attach diff from v2 to v3 here for you to refer (Or any advice about
> what next time I can do when uploading the v#N patch for reviewers to
> figure out the diff between patch sets more easily? I'd love to follow
> if it improves the review process)
>
I would have expected something like
---
v3: Renamed soft_reboot_target to soft_reboot_cmd
Explain reason for introducing a worker
<other changes made in v3>
v2: <changes made in v2>
Guenter
> Woody
>
> ---- 8< ----
>
> diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c
> index d267af37e066..8c8d214b6aa7 100644
> --- a/drivers/watchdog/softdog.c
> +++ b/drivers/watchdog/softdog.c
> @@ -51,10 +51,10 @@ 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_target;
> -module_param(soft_reboot_target, charp, 0000);
> -MODULE_PARM_DESC(soft_reboot_target,
> - "Softdog action, set reboot target (default=emergency)");
> +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);
> @@ -66,7 +66,7 @@ static struct hrtimer softdog_preticktock;
>
> static int reboot_kthread_fn(void *data)
> {
> - kernel_restart(soft_reboot_target);
> + kernel_restart(soft_reboot_cmd);
> return -EPERM; /* Should not reach here */
> }
>
> @@ -86,9 +86,26 @@ 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_target != NULL) {
> + 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,
> @@ -179,10 +196,8 @@ static int __init softdog_init(void)
> softdog_preticktock.function = softdog_pretimeout;
> }
>
> - if (soft_active_on_boot) {
> - set_bit(WDOG_HW_RUNNING, &softdog_dev.status);
> - set_bit(WDOG_ACTIVE, &softdog_dev.status);
> - }
> + if (soft_active_on_boot)
> + softdog_ping(&softdog_dev);
>
> ret = watchdog_register_device(&softdog_dev);
> if (ret)
> @@ -190,8 +205,8 @@ static int __init softdog_init(void)
>
> 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_target=%s soft_active_on_boot=%d\n",
> - soft_reboot_target, soft_active_on_boot);
> + pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n",
> + soft_reboot_cmd, soft_active_on_boot);
>
> return 0;
> }
> ---- >8 ----
>
> On Wed, Jul 1, 2020 at 10:10 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >
> > On 7/1/20 4:03 AM, 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>
> >
> > Sigh. Now I'll have to look up old versions and compare to figure out
> > changes from v2. Why do people always believe that kernel maintainers
> > have endless amounts of time available ?
> >
> > [ Sorry, yes, I know, we are supposed to remain friendly all the time.
> > It is just _so_ frustrating to have to deal with this all the time. ]
> >
> > Guenter
> >
> > > ---
> > > 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;
> > > 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);
> > >
> > > return 0;
> > > }
> > >
> >
