On Wed, Mar 23, 2016 at 09:35:50PM +0100, Mark Kettenis wrote: > > > > This doesn't only change the sched_yield() behaviour, but also > > modifies how in-kernel yield() calls behave for threaded processes. > > That is probably not right. > > So here is a diff that keeps yield() the same and adds the code in the > sched_yield(2) implementation instead. It also changes the logic that > picks the priority to walk the complete threads listand pick the > highest priotity of all the threads. That should be enough to make > sure the calling thread is scheduled behind all other threads from the > same process. That does require us to grab the kernel lock though. > So this removes NOLOCK from sched_yield(2). I don't think that is a > big issue.
I used to think that this is a hack, but now i think this is necessary. Even if one day we fix the "browsers problem" in the thread library, I think this diff will remain necessary to handle processes calling sched_yield() in a loop, i.e. processes that are spinning.
