3.16.62-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Olsa jolsa@redhat.com
commit 0933840acf7b65d6d30a5b6089d882afea57aca3 upstream.
CAI Qian reported a crash in the PMU uncore device removal code, enabled by the CONFIG_DEBUG_TEST_DRIVER_REMOVE=y option:
https://marc.info/?l=linux-kernel&m=147688837328451
The reason for the crash is that perf_pmu_unregister() tries to remove a PMU device which is not added at this point. We add PMU devices only after pmu_bus is registered, which happens in the perf_event_sysfs_init() call and sets the 'pmu_bus_running' flag.
The fix is to get the 'pmu_bus_running' flag state at the point the PMU is taken out of the PMU list and remove the device later only if it's set.
Reported-by: CAI Qian caiqian@redhat.com Tested-by: CAI Qian caiqian@redhat.com Signed-off-by: Jiri Olsa jolsa@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jiri Olsa jolsa@redhat.com Cc: Kan Liang kan.liang@intel.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Rob Herring robh@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/20161020111011.GA13361@krava Signed-off-by: Ingo Molnar mingo@kernel.org [bwh: Backported to 3.16: no address filter attributes to clean up] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6930,7 +6930,10 @@ EXPORT_SYMBOL_GPL(perf_pmu_register);
void perf_pmu_unregister(struct pmu *pmu) { + int remove_device; + mutex_lock(&pmus_lock); + remove_device = pmu_bus_running; list_del_rcu(&pmu->entry); mutex_unlock(&pmus_lock);
@@ -6944,8 +6947,10 @@ void perf_pmu_unregister(struct pmu *pmu free_percpu(pmu->pmu_disable_count); if (pmu->type >= PERF_TYPE_MAX) idr_remove(&pmu_idr, pmu->type); - device_del(pmu->dev); - put_device(pmu->dev); + if (remove_device) { + device_del(pmu->dev); + put_device(pmu->dev); + } free_pmu_context(pmu); } EXPORT_SYMBOL_GPL(perf_pmu_unregister);