Hello, On Thu, Sep 17, 2015 at 05:10:49PM +0200, Peter Zijlstra wrote: > Subject: sched: Refuse to unplug a CPU if this will violate user task affinity > > Its bad policy to allow unplugging a CPU for which a user set explicit > affinity, either strictly on this CPU or in case this was the last > online CPU in its mask. > > Either would end up forcing the thread on a random other CPU, violating > the sys_sched_setaffinity() constraint.
Shouldn't this at least handle suspend differently? Otherwise any userland task would be able to block suspend. > Disallow this by default; root might not be aware of all user > affinities, but can negotiate and change affinities for all tasks. > > Provide a sysctl to go back to the old behaviour. I don't think a sysctl is a good way to control this as that breaks the invariant - all tasks always have some cpus online in its affinity mask - which otherwise can be guaranteed. If we wanna go this way, let's plesae start the discussion in a separate thread with detailed explanation on implications of the change. Thanks. -- tejun -- 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/
