On Thu, 03 May 2012 14:29:10 +0200 Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Thu, 2012-05-03 at 21:22 +0900, Takuya Yoshikawa wrote: > > Although the real use case is out of this RFC patch, we are now discussing > > a case in which we may hold a spin_lock for long time, ms order, depending > > on workload; and in that case, other threads -- VCPU threads -- should be > > given higher priority for that problematic lock. > > Firstly, if you can hold a lock that long, it shouldn't be a spinlock, I agree with you in principle, but isn't cond_resched_lock() there for that? > secondly why isn't TIF_RESCHED being set if its running that long? That > should still make cond_resched_lock() break. I see. I did some tests using spin_is_contended() and need_resched() and saw that need_resched() was called as often as spin_is_contended(), so experimentally I understand your point. But as I could not see why spin_needbreak() was differently implemented depending on CONFIG_PREEMPT, I wanted to understand the meaning. Thanks, Takuya -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
