Messages in this thread |  | | Subject | Re: [RFC 1/3] watchdog: change watchdog_need_worker logic | From | Guenter Roeck <> | Date | Sun, 17 Jul 2016 12:49:54 -0700 |
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On 07/17/2016 12:24 PM, Wim Van Sebroeck wrote: > Hi Rasmus, > >> If the driver indicates that the watchdog is running, the framework >> should feed it until userspace opens the device, regardless of whether >> the driver has set max_hw_heartbeat_ms. >> >> This patch only affects the case where wdd->max_hw_heartbeat_ms is >> zero, wdd->timeout is non-zero, the watchdog is not active and the >> hardware device is running (*): >> >> - If wdd->timeout is zero, watchdog_need_worker() returns false both >> before and after this patch, and watchdog_next_keepalive() is not >> called. >> >> - If watchdog_active(wdd), the return value from watchdog_need_worker >> is also the same as before (namely, hm && t > hm). Hence in that case, >> watchdog_next_keepalive() is only called if hm == max_hw_heartbeat_ms >> is non-zero, so the change to min_not_zero there is a no-op. >> >> - If the watchdog is not active and the device is not running, we >> return false from watchdog_need_worker just as before. >> >> That leaves the watchdog_hw_running(wdd) && !watchdog_active(wdd) && >> wdd->timeout case. Again, it's easy to see that if >> wdd->max_hw_heartbeat_ms is non-zero, we return true from >> watchdog_need_worker with and without this patch, and the logic in >> watchdog_next_keepalive is unchanged. Finally, if >> wdd->max_hw_heartbeat_ms is 0, we used to end up in the >> cancel_delayed_work branch, whereas with this patch we end up >> scheduling a ping timeout_ms/2 from now. >> >> (*) This should imply that no current kernel drivers are affected, >> since the only drivers which explicitly set WDOG_HW_RUNNING are >> imx2_wdt.c and dw_wdt.c, both of which also provide a non-zero value >> for max_hw_heartbeat_ms. The watchdog core also sets WDOG_HW_RUNNING, >> but only when the driver doesn't provide ->stop, in which case it >> must, according to Documentation/watchdog/watchdog-kernel-api.txt, set >> max_hw_heartbeat_ms. > > This isn't completely true. We will have the following in the linux-watchdog tree: > drivers/watchdog/aspeed_wdt.c: set_bit(WDOG_HW_RUNNING, &wdt->wdd.status); > drivers/watchdog/dw_wdt.c: set_bit(WDOG_HW_RUNNING, &wdd->status); > drivers/watchdog/dw_wdt.c: set_bit(WDOG_HW_RUNNING, &wdd->status); > drivers/watchdog/imx2_wdt.c: set_bit(WDOG_HW_RUNNING, &wdog->status); > drivers/watchdog/imx2_wdt.c: set_bit(WDOG_HW_RUNNING, &wdog->status); > drivers/watchdog/max77620_wdt.c: set_bit(WDOG_HW_RUNNING, &wdt_dev->status); > drivers/watchdog/sbsa_gwdt.c: set_bit(WDOG_HW_RUNNING, &wdd->status); > drivers/watchdog/tangox_wdt.c: set_bit(WDOG_HW_RUNNING, &dev->wdt.status); > > I checked the ones that aren't mentioned and aspeed_wdt, max77620_wdt and sbsa_gwdt.c > also have a non-zero value for max_hw_heartbeat_ms. But tangox_wdt.c doesn't set it. > This one will need to be looked at closer. >
I had a brief look; the tangox_wdt problem is my fault. I overlooked that with my commit 'watchdog: tangox: Mark running watchdog correctly'.
We have a number of options: Set max_hw_heartbeat_ms in tangox_wdt.c, accept this patch, or both. I think we should accept this patch.
Thanks, Guenter
>> >> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk> >> --- >> drivers/watchdog/watchdog_dev.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c >> index 3595cff..14f8a92 100644 >> --- a/drivers/watchdog/watchdog_dev.c >> +++ b/drivers/watchdog/watchdog_dev.c >> @@ -92,9 +92,13 @@ static inline bool watchdog_need_worker(struct watchdog_device *wdd) >> * thus is aware that the framework supports generating heartbeat >> * requests. >> * - Userspace requests a longer timeout than the hardware can handle. >> + * >> + * Alternatively, if userspace has not opened the watchdog >> + * device, we take care of feeding the watchdog if it is >> + * running. >> */ >> - return hm && ((watchdog_active(wdd) && t > hm) || >> - (t && !watchdog_active(wdd) && watchdog_hw_running(wdd))); >> + return (hm && watchdog_active(wdd) && t > hm) || >> + (t && !watchdog_active(wdd) && watchdog_hw_running(wdd)); >> } >> >> static long watchdog_next_keepalive(struct watchdog_device *wdd) >> @@ -107,7 +111,7 @@ static long watchdog_next_keepalive(struct watchdog_device *wdd) >> unsigned int hw_heartbeat_ms; >> >> virt_timeout = wd_data->last_keepalive + msecs_to_jiffies(timeout_ms); >> - hw_heartbeat_ms = min(timeout_ms, wdd->max_hw_heartbeat_ms); >> + hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms); >> keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2); >> >> if (!watchdog_active(wdd)) >> -- >> 2.5.0 >> > > Kind regards, > Wim. > >
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