Messages in this thread | | | From | Alexei Starovoitov <> | Date | Fri, 19 Oct 2018 07:47:18 -0700 | Subject | Re: [RFC PATCH 1/5] x86: introduce preemption disable prefix |
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On Fri, Oct 19, 2018 at 1:22 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Oct 18, 2018 at 10:00:53PM -0700, Alexei Starovoitov wrote: > > > > > > > > > > > Another example is __BPF_PROG_RUN_ARRAY(), which also uses > > > > preempt_enable_no_resched(). > > > > > > Alexei, I think this code is just wrong. > > > > why 'just wrong' ? > > Because you lost a preemption point, this is a no-no. > > > > > > Do you know why it uses > > > preempt_enable_no_resched()? > > > > dont recall precisely. > > we could be preemptable at the point where macro is called. > > I think the goal of no_resched was to avoid adding scheduling points > > where they didn't exist before just because a prog ran for few nsec. > > May be Daniel or Roman remember. > > No, you did the exact opposite, where there previously was a preemption, > you just ate it. The band saw didn't get stopped in time, you loose your > hand etc..
Let me do few experiments then. We will fix it up.
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