perf/core: Protect PMU device removal with a 'pmu_bus_running' check, to fix CONFIG_D...

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 <[email protected]>
Tested-by: CAI Qian <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/20161020111011.GA13361@krava
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c6e47e97b33fdb7b0bbabf91016d51bc76d4b63c..a5d2e62faf7e5ad37c153bdf56faf8cf5f1cad9c 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8855,7 +8855,10 @@ 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);
 
@@ -8869,10 +8872,12 @@ 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);
-       if (pmu->nr_addr_filters)
-               device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
-       device_del(pmu->dev);
-       put_device(pmu->dev);
+       if (remove_device) {
+               if (pmu->nr_addr_filters)
+                       device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
+               device_del(pmu->dev);
+               put_device(pmu->dev);
+       }
        free_pmu_context(pmu);
 }
 EXPORT_SYMBOL_GPL(perf_pmu_unregister);