perf, x86: Avoid kfree() in CPU_STARTING

On -rt kfree() can schedule, but CPU_STARTING is before the CPU is
fully up and running. These are contradictory, so avoid it. Instead
push the kfree() to CPU_ONLINE where we're free to schedule.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kwd4j6ayld5thrscvaxgjquv@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 10 insertions, 2 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 4ee3abf20ed6..594d42513e60 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -129,6 +129,8 @@ struct cpu_hw_events {
          * AMD specific bits
          */
         struct amd_nb           *amd_nb;
+
+        void                    *kfree_on_online;
 };
 
 #define __EVENT_CONSTRAINT(c, n, m, w) {\
@@ -1466,10 +1468,12 @@ static int __cpuinit
 x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
 {
         unsigned int cpu = (long)hcpu;
+        struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
         int ret = NOTIFY_OK;
 
         switch (action & ~CPU_TASKS_FROZEN) {
         case CPU_UP_PREPARE:
+                cpuc->kfree_on_online = NULL;
                 if (x86_pmu.cpu_prepare)
                         ret = x86_pmu.cpu_prepare(cpu);
                 break;
@@ -1479,6 +1483,10 @@ x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
                         x86_pmu.cpu_starting(cpu);
                 break;
 
+        case CPU_ONLINE:
+                kfree(cpuc->kfree_on_online);
+                break;
+
         case CPU_DYING:
                 if (x86_pmu.cpu_dying)
                         x86_pmu.cpu_dying(cpu);
diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
index 941caa2e449b..ee9436c3e5d6 100644
--- a/arch/x86/kernel/cpu/perf_event_amd.c
+++ b/arch/x86/kernel/cpu/perf_event_amd.c
@@ -350,7 +350,7 @@ static void amd_pmu_cpu_starting(int cpu)
                         continue;
 
                 if (nb->nb_id == nb_id) {
-                        kfree(cpuc->amd_nb);
+                        cpuc->kfree_on_online = cpuc->amd_nb;
                         cpuc->amd_nb = nb;
                         break;
                 }
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index f88af2c2a561..3751494e70f5 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1362,7 +1362,7 @@ static void intel_pmu_cpu_starting(int cpu)
 
                 pc = per_cpu(cpu_hw_events, i).shared_regs;
                 if (pc && pc->core_id == core_id) {
-                        kfree(cpuc->shared_regs);
+                        cpuc->kfree_on_online = cpuc->shared_regs;
                         cpuc->shared_regs = pc;
                         break;
                 }