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Date: Thu, 04 Oct 2012 11:07:35 +0200 From: Peter Zijlstra <peterz@...radead.org> To: "Yan, Zheng" <zheng.z.yan@...ux.intel.com> Cc: Thomas Gleixner <tglx@...utronix.de>, linux-kernel <linux-kernel@...r.kernel.org>, Stephane Eranian <eranian@...gle.com>, mingo@...nel.org Subject: uncore doing kfree() from CPU_{STARTING,DYING} Hi Zheng, Can you have a look at 7fdba1ca and do a similar patch for uncore? Thomas is sad because uncore breaks -rt, the problem (as described in that patch) is that kfree() must schedule on -rt while CPU_{STARTING,DYING} really are atomic. ~ Peter --- commit 7fdba1ca10462f42ad2246b918fe6368f5ce488e Author: Peter Zijlstra <a.p.zijlstra@...llo.nl> Date: Fri Jul 22 13:41:54 2011 +0200 perf, x86: Avoid kfree() in CPU_STARTING On -rt kfree() can schedule, but CPU_STARTING is before the CPU is fully up and running. These are contradictory, so avoid it. Instead push the kfree() to CPU_ONLINE where we're free to schedule. Reported-by: Thomas Gleixner <tglx@...utronix.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl> Link: http://lkml.kernel.org/n/tip-kwd4j6ayld5thrscvaxgjquv@git.kernel.org Signed-off-by: Ingo Molnar <mingo@...e.hu> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 4ee3abf..594d425 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -129,6 +129,8 @@ struct cpu_hw_events { * AMD specific bits */ struct amd_nb *amd_nb; + + void *kfree_on_online; }; #define __EVENT_CONSTRAINT(c, n, m, w) {\ @@ -1466,10 +1468,12 @@ static int __cpuinit x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu) { unsigned int cpu = (long)hcpu; + struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu); int ret = NOTIFY_OK; switch (action & ~CPU_TASKS_FROZEN) { case CPU_UP_PREPARE: + cpuc->kfree_on_online = NULL; if (x86_pmu.cpu_prepare) ret = x86_pmu.cpu_prepare(cpu); break; @@ -1479,6 +1483,10 @@ x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu) x86_pmu.cpu_starting(cpu); break; + case CPU_ONLINE: + kfree(cpuc->kfree_on_online); + break; + case CPU_DYING: if (x86_pmu.cpu_dying) x86_pmu.cpu_dying(cpu); diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c index 941caa2..ee9436c 100644 --- a/arch/x86/kernel/cpu/perf_event_amd.c +++ b/arch/x86/kernel/cpu/perf_event_amd.c @@ -350,7 +350,7 @@ static void amd_pmu_cpu_starting(int cpu) continue; if (nb->nb_id == nb_id) { - kfree(cpuc->amd_nb); + cpuc->kfree_on_online = cpuc->amd_nb; cpuc->amd_nb = nb; break; } diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c index f88af2c..3751494 100644 --- a/arch/x86/kernel/cpu/perf_event_intel.c +++ b/arch/x86/kernel/cpu/perf_event_intel.c @@ -1362,7 +1362,7 @@ static void intel_pmu_cpu_starting(int cpu) pc = per_cpu(cpu_hw_events, i).shared_regs; if (pc && pc->core_id == core_id) { - kfree(cpuc->shared_regs); + cpuc->kfree_on_online = cpuc->shared_regs; cpuc->shared_regs = pc; break; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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