Messages in this thread | | | Subject | Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge | From | Peter Zijlstra <> | Date | Fri, 08 Jun 2012 20:49:01 +0200 |
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On Fri, 2012-06-08 at 18:28 +0200, Stephane Eranian wrote: > > static int apply_microcode_on_target(int cpu) > > { > > struct apply_microcode_ctx ctx = { .err = 0 }; > > int ret; > > > > + ret = microcode_notifier_check(ucode_cpu_info + cpu); > > + if (ret) > > + return ret; > > + > > ret = smp_call_function_single(cpu, apply_microcode_local, &ctx, 1); > > if (!ret) > > ret = ctx.err; > > > > + if (!ret) > > + microcode_notifier_done(); > > + > I suspect you want to do this here and not after the update() has completed over > all CPU (for_each_online_cpu()), because you want to prevent a race condition > with perf_event users trying PEBS at the same time. If not, then why not move > the callback after all the smp_call() are done.
Because not all callers are in a for_each_cpu loop. For instance, see the reload_store() thing.
Also, since the ucode is per-cpu and not machine wide, a per-cpu callback makes more sense.
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