On Tuesday, May 28, 2013 11:26:09 AM Zoran Markovic wrote: > > What about this: > > - Add one more list_head to struct dev_pm_info. > > - Make dpm_prepare() create a new list for the next steps instead of moving > > devices out of dpm_list. > > - Start an async work to carry out dpm_suspend() and make the main thread > > do wait_for_completion_timeout() for every device in dpm_list (in the > > reverse order). > > - If it times out, mark the device in question as unusable, possibly resume > > the already suspended devices (except for descendants of the failed one) > > and abort the suspend. Return a specific error code to user space so > > that > > it knows what happened. [You can make this step configurable to BUG() > > instead of doing all those things if you think that will be more useful > > for > > platforms you care about.] > > - Disable future suspends. > > And analogously for resume. > > > > That should allow people to investigate what happened on a system that > > (hopefully) is not completely dead and you still can have your "reboot if > > suspend hangs" feature if you like. > > I looked into implementing this. The problem that I encountered is > that there is no reliable way of canceling an async task, and hence > the asynchronous __device_suspend() would be left racing with a > recovery from a suspend timeout.
Why exactly would it be racing? We wouldn't call device_resume() for the device that timed out (and its descendants). > We could do cancel_work_sync() as a recovery, but that call blocks until the > running async task is flushed, which might never happen. So doing a panic() > is pretty much the only option for recovering. Well, its usefulness is quite limited, then. That said I'm still not convinced that this actually is the case. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
