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authorRasmus Villemoes <rasmus.villemoes@prevas.dk>2016-07-14 12:16:26 +0300
committerWim Van Sebroeck <wim@iguana.be>2016-07-17 22:25:53 +0300
commit3fbfe9264756d3fd99a9210345016c94ec4ada73 (patch)
tree32a9bd509e1e29283cff4c4e7ebdf9671e082b29 /drivers/watchdog
parent65b5b5e6480718e8cb5b6a1d32a7cb4efb9d93a9 (diff)
downloadlinux-3fbfe9264756d3fd99a9210345016c94ec4ada73.tar.xz
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 <rasmus.villemoes@prevas.dk> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Diffstat (limited to 'drivers/watchdog')
-rw-r--r--drivers/watchdog/watchdog_dev.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 3595cffa24ea..14f8a92fca12 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))