Messages in this thread Patch in this message | | | From | Andi Kleen <> | Subject | [PATCH] perf, x86, uncore: Fix minor race in box set up | Date | Mon, 22 Sep 2014 15:27:06 -0700 |
| |
From: Andi Kleen <ak@linux.intel.com>
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 <ak@linux.intel.com> --- 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 812ec5d..76fa7e3 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); -- 1.9.3
| |