On 11/30/2015 08:47 PM, Linus Torvalds wrote: > On Mon, Nov 30, 2015 at 5:34 PM, Sasha Levin <sasha.le...@oracle.com> wrote: >> Futex can have a spurious wake up before we actually wake it up on our own, >> which will trigger this warning if the task is still stopped. > > Actually, I think it would presumably be the other way around: a > spurious stale futex wakeup happens *after* the process has been woken > up for some other reason and moved to stopped state. > > (The "wake up and move to stopped state" could be for the same reason: > a SIGSTOP signal). > > So the setup is presumably something like this: > > - on cpu1: futex code is about to go to sleep, adds itself to the > futex hash chains, but then gets interrupted by a SIGSTOP > > - in the meantime, on cpu2, the futex is changed, and the wakup code > sees the process from cpu1 on the futex hash chains > > - on cpu1, the process has now removed itself from the hash chains, > and goes through the signal code that sets the state to STOPPED > > - in the meantime, on cpu2, the futex code now gets around to waking > things up, and sees that stopped state > > Roughly.
What would the correct behaviour in that case be? Does waking up the task while it is being traced, and ptrace (or gdb) is not expecting a wakeup, break the tracing? -- All rights reversed -- 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/
