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Groups > linux.kernel > #1642297
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order |
| Date | 2017-05-16 10:20 +0200 |
| Message-ID | <tHFS1-3bj-7@gated-at.bofh.it> (permalink) |
| References | (1 earlier) <tGoTf-139-9@gated-at.bofh.it> <tGqs1-2k3-11@gated-at.bofh.it> <tGFAK-4lQ-9@gated-at.bofh.it> <tHkaU-67d-55@gated-at.bofh.it> <tHtea-3jL-19@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon, May 15, 2017 at 11:40:43AM -0700, Paul E. McKenney wrote:
> Given that you acquire the global pmus_lock when doing the
> get_online_cpus(), and given that CPU hotplug is rare, is it possible
> to momentarily acquire the global pmus_lock in perf_event_init_cpu()
> and perf_event_exit_cpu() and interact directly with that? Then perf
> would presumably leave alone any outgoing CPU that had already executed
> perf_event_exit_cpu(), and also any incoming CPU that had not already
> executed perf_event_init_cpu().
>
> What prevents this approach from working?
Lack of sleep probably ;-)
I'd blame the kids, but those have actually been very good lately.
You're suggesting the below on top, right? I'll run it with lockdep
enabled after I chase some regression..
---
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8997,7 +8997,6 @@ int perf_pmu_register(struct pmu *pmu, c
{
int cpu, ret;
- get_online_cpus();
mutex_lock(&pmus_lock);
ret = -ENOMEM;
pmu->pmu_disable_count = alloc_percpu(int);
@@ -9093,7 +9092,6 @@ int perf_pmu_register(struct pmu *pmu, c
ret = 0;
unlock:
mutex_unlock(&pmus_lock);
- put_online_cpus();
return ret;
@@ -11002,10 +11000,9 @@ static void perf_event_exit_cpu_context(
struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx;
struct pmu *pmu;
- int idx;
- idx = srcu_read_lock(&pmus_srcu);
- list_for_each_entry_rcu(pmu, &pmus, entry) {
+ mutex_lock(&pmus_lock);
+ list_for_each_entry(pmu, &pmus, entry) {
cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
ctx = &cpuctx->ctx;
@@ -11014,7 +11011,7 @@ static void perf_event_exit_cpu_context(
cpuctx->online = 0;
mutex_unlock(&ctx->mutex);
}
- srcu_read_unlock(&pmus_srcu, idx);
+ mutex_unlock(&pmus_lock);
}
#else
@@ -11027,12 +11024,11 @@ int perf_event_init_cpu(unsigned int cpu
struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx;
struct pmu *pmu;
- int idx;
perf_swevent_init_cpu(cpu);
- idx = srcu_read_lock(&pmus_srcu);
- list_for_each_entry_rcu(pmu, &pmus, entry) {
+ mutex_lock(&pmus_lock);
+ list_for_each_entry(pmu, &pmus, entry) {
cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
ctx = &cpuctx->ctx;
@@ -11040,7 +11036,7 @@ int perf_event_init_cpu(unsigned int cpu
cpuctx->online = 1;
mutex_unlock(&ctx->mutex);
}
- srcu_read_unlock(&pmus_srcu, idx);
+ mutex_unlock(&pmus_lock);
return 0;
}
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[RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 19:30 +0200
[RFC][PATCH 5/5] perf: Grab event_mutex before taking get_online_cpus() Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 19:30 +0200
[RFC][PATCH 3/5] kprobes: Take get_online_cpus() before taking jump_label_lock() Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 19:30 +0200
Re: [RFC][PATCH 3/5] kprobes: Take get_online_cpus() before taking jump_label_lock() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-12 20:40 +0200
Re: [RFC][PATCH 3/5] kprobes: Take get_online_cpus() before taking jump_label_lock() Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 20:50 +0200
Re: [RFC][PATCH 3/5] kprobes: Take get_online_cpus() before taking jump_label_lock() Masami Hiramatsu <mhiramat@kernel.org> - 2017-05-17 20:00 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-12 20:20 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Peter Zijlstra <peterz@infradead.org> - 2017-05-12 22:00 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 22:20 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 23:40 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-13 15:50 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Peter Zijlstra <peterz@infradead.org> - 2017-05-15 11:10 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-15 20:50 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Peter Zijlstra <peterz@infradead.org> - 2017-05-16 10:20 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-16 14:50 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-16 16:30 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Peter Zijlstra <peterz@infradead.org> - 2017-05-17 12:50 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-17 17:00 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-18 06:00 +0200
Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Steven Rostedt <rostedt@goodmis.org> - 2017-05-15 21:10 +0200
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