78 lines
3.2 KiB
Diff
78 lines
3.2 KiB
Diff
From: Julia Cartwright <julia@ni.com>
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Date: Fri, 28 Sep 2018 21:03:51 +0000
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Subject: [PATCH 252/290] watchdog: prevent deferral of watchdogd wakeup on RT
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Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=4d37485d195e0b7f778a9556486f4b63c3acd32a
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When PREEMPT_RT_FULL is enabled, all hrtimer expiry functions are
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deferred for execution into the context of ktimersoftd unless otherwise
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annotated.
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Deferring the expiry of the hrtimer used by the watchdog core, however,
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is a waste, as the callback does nothing but queue a kthread work item
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and wakeup watchdogd.
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It's worst then that, too: the deferral through ktimersoftd also means
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that for correct behavior a user must adjust the scheduling parameters
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of both watchdogd _and_ ktimersoftd, which is unnecessary and has other
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side effects (like causing unrelated expiry functions to execute at
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potentially elevated priority).
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Instead, mark the hrtimer used by the watchdog core as being _HARD to
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allow it's execution directly from hardirq context. The work done in
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this expiry function is well-bounded and minimal.
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A user still must adjust the scheduling parameters of the watchdogd
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to be correct w.r.t. their application needs.
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Cc: Guenter Roeck <linux@roeck-us.net>
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Reported-and-tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
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Reported-by: Tim Sander <tim@krieglstein.org>
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Signed-off-by: Julia Cartwright <julia@ni.com>
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Acked-by: Guenter Roeck <linux@roeck-us.net>
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[bigeasy: use only HRTIMER_MODE_REL_HARD]
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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drivers/watchdog/watchdog_dev.c | 8 ++++----
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1 file changed, 4 insertions(+), 4 deletions(-)
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diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
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index ffbdc4642ea5..84f75b5045f6 100644
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--- a/drivers/watchdog/watchdog_dev.c
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+++ b/drivers/watchdog/watchdog_dev.c
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@@ -147,7 +147,7 @@ static inline void watchdog_update_worker(struct watchdog_device *wdd)
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ktime_t t = watchdog_next_keepalive(wdd);
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if (t > 0)
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- hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL);
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+ hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL_HARD);
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} else {
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hrtimer_cancel(&wd_data->timer);
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}
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@@ -166,7 +166,7 @@ static int __watchdog_ping(struct watchdog_device *wdd)
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if (ktime_after(earliest_keepalive, now)) {
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hrtimer_start(&wd_data->timer,
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ktime_sub(earliest_keepalive, now),
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- HRTIMER_MODE_REL);
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+ HRTIMER_MODE_REL_HARD);
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return 0;
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}
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@@ -945,7 +945,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
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return -ENODEV;
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kthread_init_work(&wd_data->work, watchdog_ping_work);
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- hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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+ hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
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wd_data->timer.function = watchdog_timer_expired;
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if (wdd->id == 0) {
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@@ -992,7 +992,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
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__module_get(wdd->ops->owner);
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kref_get(&wd_data->kref);
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if (handle_boot_enabled)
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- hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL);
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+ hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL_HARD);
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else
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pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
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wdd->id);
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