kernel.git/drivers/watchdog/watchdog_dev.c, branch linux-4.8.y

watchdog: core: Clear WDOG_HW_RUNNING before calling the stop function

2016-07-25T10:03:04Z

WDOG_HW_RUNNING indicates that the hardware watchdog is running while the watchdog device is closed. The flag may be set by the driver when it is instantiated to indicate that the watchdog is running, and that the watchdog core needs to send heartbeat requests to the driver until the watchdog device is opened. When the watchdog device is closed, the flag can be used by the driver's stop function to indicate to the watchdog core that it was unable to stop the watchdog, and that the watchdog core needs to send heartbeat requests. This only works if the flag is actually cleared when the watchdog is stopped. To avoid having to clear the flag in each driver's stop function, clear it in the watchdog core before calling the stop function. Reported-by: Rasmus Villemoes Fixes: ee142889e32f ("watchdog: Introduce WDOG_HW_RUNNING flag") Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: core: Fix error handling of watchdog_dev_init()

2016-07-25T10:02:55Z

Fix the error handling paths of watchdog_dev_init(). Signed-off-by: Wei Yongjun Reviewed-by: Guenter Roeck Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: Implement status function in watchdog core

2016-07-19T08:09:07Z

Up to now, the watchdog status function called a driver function, which was supposed to return the watchdog status. All but one driver using the watchdog core did not implement this function, and the driver implementing it did not implement it correctly (the function is supposed to return WDIOF_ flags). At the same time, at least some of the status information can be provided by the watchdog core. Provide the available status bits directly from the watchdog driver core. Call the driver status function if it exists to get the boot status, but always provide WDIOF_MAGICCLOSE and WDIOF_KEEPALIVEPING internally. This patch makes the 'status' sysfs attribute always available. This attribute is now displayed as hex number with 0x prepended to be easier to decode. Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: change watchdog_need_worker logic

2016-07-17T19:25:53Z

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

watchdog: core: Fix circular locking dependency

2016-05-14T14:10:33Z

lockdep reports the following circular locking dependency. ====================================================== INFO: possible circular locking dependency detected ] 4.6.0-rc3-00191-gfabf418 #162 Not tainted ------------------------------------------------------- systemd/1 is trying to acquire lock: ((&(&wd_data->work)->work)){+.+...}, at: [<80141650>] flush_work+0x0/0x280 but task is already holding lock: (&wd_data->lock){+.+...}, at: [<804acfa8>] watchdog_release+0x18/0x190 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&wd_data->lock){+.+...}: [<80662310>] mutex_lock_nested+0x64/0x4a8 [<804aca4c>] watchdog_ping_work+0x18/0x4c [<80143128>] process_one_work+0x1ac/0x500 [<801434b4>] worker_thread+0x38/0x554 [<80149510>] kthread+0xf4/0x108 [<80107c10>] ret_from_fork+0x14/0x24 -> #0 ((&(&wd_data->work)->work)){+.+...}: [<8017c4e8>] lock_acquire+0x70/0x90 [<8014169c>] flush_work+0x4c/0x280 [<801440f8>] __cancel_work_timer+0x9c/0x1e0 [<804acfcc>] watchdog_release+0x3c/0x190 [<8022c5e8>] __fput+0x80/0x1c8 [<80147b28>] task_work_run+0x94/0xc8 [<8010b998>] do_work_pending+0x8c/0xb4 [<80107ba8>] slow_work_pending+0xc/0x20 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&wd_data->lock); lock((&(&wd_data->work)->work)); lock(&wd_data->lock); lock((&(&wd_data->work)->work)); *** DEADLOCK *** 1 lock held by systemd/1: stack backtrace: CPU: 2 PID: 1 Comm: systemd Not tainted 4.6.0-rc3-00191-gfabf418 #162 Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) [<8010f5e4>] (unwind_backtrace) from [<8010c038>] (show_stack+0x10/0x14) [<8010c038>] (show_stack) from [<8039d7fc>] (dump_stack+0xa8/0xd4) [<8039d7fc>] (dump_stack) from [<80177ee0>] (print_circular_bug+0x214/0x334) [<80177ee0>] (print_circular_bug) from [<80179230>] (check_prevs_add+0x4dc/0x8e8) [<80179230>] (check_prevs_add) from [<8017b3d8>] (__lock_acquire+0xc6c/0x14ec) [<8017b3d8>] (__lock_acquire) from [<8017c4e8>] (lock_acquire+0x70/0x90) [<8017c4e8>] (lock_acquire) from [<8014169c>] (flush_work+0x4c/0x280) [<8014169c>] (flush_work) from [<801440f8>] (__cancel_work_timer+0x9c/0x1e0) [<801440f8>] (__cancel_work_timer) from [<804acfcc>] (watchdog_release+0x3c/0x190) [<804acfcc>] (watchdog_release) from [<8022c5e8>] (__fput+0x80/0x1c8) [<8022c5e8>] (__fput) from [<80147b28>] (task_work_run+0x94/0xc8) [<80147b28>] (task_work_run) from [<8010b998>] (do_work_pending+0x8c/0xb4) [<8010b998>] (do_work_pending) from [<80107ba8>] (slow_work_pending+0xc/0x20) Turns out the call to cancel_delayed_work_sync() in watchdog_release() is not necessary and can be dropped. If the worker is no longer necessary, the subsequent call to watchdog_update_worker() will cancel it. If it is already running, it won't do anything, since the worker function checks if it needs to ping the watchdog or not. Reported-by: Clemens Gruber Tested-by: Clemens Gruber Fixes: 11d7aba9ceb7 ("watchdog: imx2: Convert to use infrastructure triggered keepalives") Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck Cc: stable

watchdog: Ensure that wdd is not dereferenced if NULL

2016-03-16T20:11:50Z

Smatch rightfully complains that wdd is dereferenced in the watchdog release function after being checked for NULL. Also make sure that it is not accessed outside mutex protection to avoid use-after-free problems. Fixes: e6c71e84e4c0 ("watchdog: Introduce WDOG_HW_RUNNING flag") Reported-by: Dan Carpenter Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: Add support for minimum time between heartbeats

2016-03-16T20:11:19Z

Some watchdogs require a minimum time between heartbeats. Examples are the watchdogs in DA9062 and AT91SAM9x. Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: Make stop function optional

2016-03-16T20:11:16Z

Not all hardware watchdogs can be stopped. The driver for such watchdogs would typically only set the WATCHDOG_HW_RUNNING flag in its stop function. Make the stop function optional and set WATCHDOG_HW_RUNNING in the watchdog core if it is not provided. Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: Introduce WDOG_HW_RUNNING flag

2016-03-16T20:11:15Z

The WDOG_HW_RUNNING flag is expected to be set by watchdog drivers if the hardware watchdog is running. If the flag is set, the watchdog subsystem will ping the watchdog even if the watchdog device is closed. The watchdog driver stop function is now optional and may be omitted if the watchdog can not be stopped. If stopping the watchdog is not possible but the driver implements a stop function, it is responsible to set the WDOG_HW_RUNNING flag in its stop function. Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck

watchdog: Introduce hardware maximum heartbeat in watchdog core

2016-03-16T20:11:14Z

Introduce an optional hardware maximum heartbeat in the watchdog core. The hardware maximum heartbeat can be lower than the maximum timeout. Drivers can set the maximum hardware heartbeat value in the watchdog data structure. If the configured timeout exceeds the maximum hardware heartbeat, the watchdog core enables a timer function to assist sending keepalive requests to the watchdog driver. Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck