On Thu, 2013-06-06 at 20:08 -0700, Greg KH wrote: > On Fri, Jun 07, 2013 at 10:37:52AM +0800, Yanmin Zhang wrote: > > On Thu, 2013-06-06 at 18:02 -0700, Greg KH wrote: > > > On Fri, Jun 07, 2013 at 08:53:29AM +0800, Yanmin Zhang wrote: > > > > On Thu, 2013-06-06 at 15:18 +0200, Thomas Gleixner wrote: > > > > > On Thu, 6 Jun 2013, shuox....@intel.com wrote: > > > > > > From: Zhang Yanmin <yanmin.zh...@intel.com> > > > > > > > > > > > > synchronize_irq waits pending IRQ handlers to be finished. If using > > > > > > this > > > > > > function while holding a resource, the IRQ handler may cause > > > > > > deadlock. > > > > > > > > > > > > Here we add a new function irq_in_progress which doesn't wait for > > > > > > the handlers > > > > > > to be finished. > > > > > > > > > > > > A typical use case at suspend-to-ram: > > > > > > > > > > > > device driver's irq handler is complicated and might hold a mutex > > > > > > at rare cases. > > > > > > Its suspend function is called and a suspended flag is set. > > > > > > In case its IRQ handler is running, suspend function calls > > > > > > irq_in_progress. if > > > > > > handler is running, abort suspend. > > > > > > The irq handler checks the suspended flag. If the device is > > > > > > suspended, irq handler > > > > > > either ignores the interrupt, or wakes up the whole system, and the > > > > > > driver's > > > > > > resume function could deal with the delayed interrupt handling. > > > > > > > > > > This is as wrong as it can be. Fix the driver instead of hacking racy > > > > > functions into the core code. > > > > > > > > > > So your problem looks like this: > > > > > > > > > > CPU 0 CPU 1 > > > > > irq_handler_thread() suspend() > > > > > ..... mutex_lock(&m); > > > > > mutex_lock(&m); synchronize_irq(); > > > > > > > > > > So why needs the mutex to be taken before synchronize_irq()? Why not > > > > > doing the obvious? > > > > > > > > > > suspend() > > > > > disable_irq(); (Implies synchronize_irq) > > > > > mutex_lock(&m); > > > > > .... > > > > > mutex_unlock(&m); > > > > > enable_irq(); > > > > Thanks for the kind comment. > > > > > > > > We do consider your solution before and it works well indeed with some > > > > specific > > > > simple drivers. For example, some drives use GPIO pin as interrupt > > > > source. > > > > > > > > On one specific platform, disable_irq would really disable the irq at > > > > RTE entry, > > > > which means we lose the wakeup capability of this device. > > > > synchronize_irq can be another solution. But we did hit 'DPM device > > > > timeout' issue > > > > reported by dpm_wd_handler at suspend-to-ram. > > > > > > > > The driver is complicated. We couldn't change too many functions to > > > > optimize it. > > > > In addition, we have to use the driver instead of throwing it away. > > > > > > What is preventing you from rewriting it to work properly? > > It's complicated. > > That sounds like your issue, not ours, so please don't push the problem > onto someone else. Take ownership of the driver, fix it up, and all > will be good. > > > > > > With irq_in_progress, we can resolve this issue and it does work, > > > > although it > > > > looks like ugly. > > > > > > Don't paper over driver bugs in the core kernel, fix the driver. > > It's hard to say it's a driver bug. Could generic kernel provide some > > flexibility for such complicated drivers? > > Please post the code for the driver, and then we will be glad to > continue the dicussion. Greg,
Thanks for your enthusiasm. It's a private driver for products. Let's stop here and I wouldn't push the patch to upstream. Thanks all. Yanmin > > As for "complicated", just make it "uncomplicated", it's just code :) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
