diff options
Diffstat (limited to 'debian/patches-rt/0250-watchdog-prevent-deferral-of-watchdogd-wakeup-on-RT.patch')
| -rw-r--r-- | debian/patches-rt/0250-watchdog-prevent-deferral-of-watchdogd-wakeup-on-RT.patch | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/debian/patches-rt/0250-watchdog-prevent-deferral-of-watchdogd-wakeup-on-RT.patch b/debian/patches-rt/0250-watchdog-prevent-deferral-of-watchdogd-wakeup-on-RT.patch new file mode 100644 index 000000000..c9d461226 --- /dev/null +++ b/debian/patches-rt/0250-watchdog-prevent-deferral-of-watchdogd-wakeup-on-RT.patch @@ -0,0 +1,81 @@ +From 2536bb24992f08158455b5ad1434f439f6543db5 Mon Sep 17 00:00:00 2001 +From: Julia Cartwright <julia@ni.com> +Date: Fri, 28 Sep 2018 21:03:51 +0000 +Subject: [PATCH 250/347] watchdog: prevent deferral of watchdogd wakeup on RT +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +When PREEMPT_RT_FULL is enabled, all hrtimer expiry functions are +deferred for execution into the context of ktimersoftd unless otherwise +annotated. + +Deferring the expiry of the hrtimer used by the watchdog core, however, +is a waste, as the callback does nothing but queue a kthread work item +and wakeup watchdogd. + +It's worst then that, too: the deferral through ktimersoftd also means +that for correct behavior a user must adjust the scheduling parameters +of both watchdogd _and_ ktimersoftd, which is unnecessary and has other +side effects (like causing unrelated expiry functions to execute at +potentially elevated priority). + +Instead, mark the hrtimer used by the watchdog core as being _HARD to +allow it's execution directly from hardirq context. The work done in +this expiry function is well-bounded and minimal. + +A user still must adjust the scheduling parameters of the watchdogd +to be correct w.r.t. their application needs. + +Cc: Guenter Roeck <linux@roeck-us.net> +Reported-and-tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de> +Reported-by: Tim Sander <tim@krieglstein.org> +Signed-off-by: Julia Cartwright <julia@ni.com> +Acked-by: Guenter Roeck <linux@roeck-us.net> +[bigeasy: use only HRTIMER_MODE_REL_HARD] +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + drivers/watchdog/watchdog_dev.c | 8 ++++---- + 1 file changed, 4 insertions(+), 4 deletions(-) + +diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c +index 8fe59b7d8eec..516782cff8d2 100644 +--- a/drivers/watchdog/watchdog_dev.c ++++ b/drivers/watchdog/watchdog_dev.c +@@ -145,7 +145,7 @@ static inline void watchdog_update_worker(struct watchdog_device *wdd) + ktime_t t = watchdog_next_keepalive(wdd); + + if (t > 0) +- hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL); ++ hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL_HARD); + } else { + hrtimer_cancel(&wd_data->timer); + } +@@ -164,7 +164,7 @@ static int __watchdog_ping(struct watchdog_device *wdd) + if (ktime_after(earliest_keepalive, now)) { + hrtimer_start(&wd_data->timer, + ktime_sub(earliest_keepalive, now), +- HRTIMER_MODE_REL); ++ HRTIMER_MODE_REL_HARD); + return 0; + } + +@@ -959,7 +959,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd) + dev_set_name(&wd_data->dev, "watchdog%d", wdd->id); + + kthread_init_work(&wd_data->work, watchdog_ping_work); +- hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); ++ hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); + wd_data->timer.function = watchdog_timer_expired; + + if (wdd->id == 0) { +@@ -1007,7 +1007,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd) + __module_get(wdd->ops->owner); + get_device(&wd_data->dev); + if (handle_boot_enabled) +- hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL); ++ hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL_HARD); + else + pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n", + wdd->id); +-- +2.36.1 + |