On Fri, Sep 29, 2017 at 09:59:55AM +0200, Thomas Gleixner wrote: > On Thu, 28 Sep 2017, Junaid Shahid wrote: > > > Hi Peter, > > > > It looks like try_cmpxchg is not available on non-x86 archs, but other than > > that the version that you proposed looks good. > > > > One thing that I am a bit curious about is that the original code, before > > either patch, had a test_and_set_bit for KTHREAD_IS_PARKED rather than just > > a set_bit. I can't think of any reason why that was needed, since it > > doesn't look like TASK_PARKED tasks are susceptible to spurious wakeups. Do > > you by any chance happen to know if there was any specific reason for it? > > Everything is susceptible to spurious wakeups and has to deal with it.
Right, we should code as if they are at all times possible. Currently, for TASK_PARKED, I don't think they can happen, but I've had patches that introduce them on purpose (regardless the state) just to stress the code. IIRC only TASK_STOPPED and/or TASK_TRACED hard rely on not getting any.
