Hi Zheng,
Can you have a look at 7fdba1ca and do a similar patch for uncore?
Thomas is sad because uncore breaks -rt, the problem (as described in
that patch) is that kfree() must schedule on -rt while
CPU_{STARTING,DYING} really are atomic.
~ Peter
---
commit 7fdba1ca10462f42ad2246b918fe6368f5ce488e
Author: Peter Zijlstra <a.p.zijls...@chello.nl>
Date: Fri Jul 22 13:41:54 2011 +0200
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 <t...@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
Link: http://lkml.kernel.org/n/tip-kwd4j6ayld5thrscvaxgj...@git.kernel.org
Signed-off-by: Ingo Molnar <mi...@elte.hu>
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 4ee3abf..594d425 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 941caa2..ee9436c 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 f88af2c..3751494 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;
}
--
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