On Mon, Aug 03, 2015 at 07:13:26PM -0700, Guenter Roeck wrote: > - Some watchdogs have a very short maximum timeout, in the range of just a few > seconds. Such low timeouts are difficult if not impossible to support from > user space. Drivers supporting such watchdog hardware need to implement > a timer function to augment heartbeats from user space. > - A new status flag, WDOG_RUNNING, informs the watchdog subsystem that a > watchdog is running, and that the watchdog subsystem needs to generate > heartbeat requests while the associated watchdog device is closed. > Patch #2 adds timer functionality to the watchdog core. It solves the problem > of short maximum hardware timeouts by augmenting heartbeats triggered from > user space with internally triggered heartbeats. > > Patch #3 adds functionality to generate heartbeats while the watchdog device is > closed. It handles situation where where the watchdog is running after > the driver has been instantiated, but the device is not yet opened, > and post-close situations necessary if a watchdog can not be stopped. These sound concerning because it seems that heartbeats could be generated outside of the direct control of userspace. I have a program that depends on having direct control over whether heartbeats are generated (or more specifically, *not* generated.) If these new features introduce a new way for heartbeats to be generated, is there a way I can detect or disable that behavior from userspace? Unwanted heartbeats could break my program and may lead to data corruption. A related issue from some years ago is the unfortunate fact that closing the watchdog device also generates a heartbeat. I'd like to disable that also, and submitted a patch for it here: http://www.spinics.net/lists/linux-watchdog/msg01477.html (Without the patch, I have to work around it by closing the device prematurely as a way to generate the potentially final heartbeat, and then reopen it again if I want to continue the heartbeats.) Dave -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
