From 3fbfe9264756d3fd99a9210345016c94ec4ada73 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Thu, 14 Jul 2016 11:16:26 +0200 Subject: watchdog: change watchdog_need_worker logic 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. Signed-off-by: Rasmus Villemoes Reviewed-by: Guenter Roeck Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck 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)) -- cgit v0.10.2