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| author | Andi Kleen <ak@linux.intel.com> | 2014-09-22 15:27:06 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2014-10-03 06:02:49 +0200 |
| commit | 4f971248bc6ad2bb2a89a25a072ebfec5757d298 (patch) | |
| tree | 0b3282180645dc7e7c9010e3c55b0721f9350d9c /arch/x86/kernel/cpu | |
| parent | 69e8f5b15ef43da1e177665a3e2063711ee4c9de (diff) | |
| download | blackbird-obmc-linux-4f971248bc6ad2bb2a89a25a072ebfec5757d298.tar.gz blackbird-obmc-linux-4f971248bc6ad2bb2a89a25a072ebfec5757d298.zip | |
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 <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: eranian@google.com
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Link: http://lkml.kernel.org/r/1411424826-15629-1-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event_intel_uncore.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c index 42d00e53175d..9762dbd9f3f7 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); |
