Hi Guenter, > 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. We accept this patch and add a fix for tangox_wdt.c . > > Thanks, > Guenter > > >> > >>Signed-off-by: Rasmus Villemoes <rasmus.villemoes@xxxxxxxxx> > >>--- > >> 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. > > > > > Kind regards, Wim. -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
