Commit-ID: 4f971248bc6ad2bb2a89a25a072ebfec5757d298 Gitweb: http://git.kernel.org/tip/4f971248bc6ad2bb2a89a25a072ebfec5757d298 Author: Andi Kleen <[email protected]> AuthorDate: Mon, 22 Sep 2014 15:27:06 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 3 Oct 2014 06:02:49 +0200
perf/x86/intel/uncore: Fix minor race in box set up I was looking for the trinity oops cause in the uncore driver. (so far didn't found it) However I found this tiny race: when a box is set up two threads on the same CPU, they may be setting up the box in parallel (e.g. with kernel preemption). This could lead to the reference count being increasing too much. Always recheck there is no existing cpu reference inside the lock. Signed-off-by: Andi Kleen <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: [email protected] Cc: Arnaldo Carvalho de Melo <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/cpu/perf_event_intel_uncore.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c index 42d00e5..9762dbd 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c +++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c @@ -42,6 +42,9 @@ struct intel_uncore_box *uncore_pmu_to_box(struct intel_uncore_pmu *pmu, int cpu return box; raw_spin_lock(&uncore_box_lock); + /* Recheck in lock to handle races. */ + if (*per_cpu_ptr(pmu->box, cpu)) + goto out; list_for_each_entry(box, &pmu->box_list, list) { if (box->phys_id == topology_physical_package_id(cpu)) { atomic_inc(&box->refcnt); @@ -49,6 +52,7 @@ struct intel_uncore_box *uncore_pmu_to_box(struct intel_uncore_pmu *pmu, int cpu break; } } +out: raw_spin_unlock(&uncore_box_lock); return *per_cpu_ptr(pmu->box, cpu); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
