From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Frederic Weisbecker <fweisbec@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
kvm-devel <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: ftrace/perf_event leak
Date: Wed, 01 Sep 2010 11:04:28 +0200 [thread overview]
Message-ID: <1283331868.2059.808.camel@laptop> (raw)
In-Reply-To: <4C7E11E5.1040402@redhat.com>
On Wed, 2010-09-01 at 11:42 +0300, Avi Kivity wrote:
> I recently added perf_event support to kvm_stat, to display kvm
> tracepoints as statistics (I'd like to fold this to tools/perf
> eventually, but that's another story). However I'm seeing a resource
> leak - after I quit the tool, there are quite a few references into the
> kvm module:
>
> kvm_intel 43655 0
> kvm 272984 269 kvm_intel
>
> The tool is just a python script that reads
> /sys/kernel/debug/tracing/events/kvm to find out which events are
> available, uses perf_event_open() to create one group per cpu to which a
> lot of events are attached. The only special thing I can think of is
> that we use an ioctl to attach a filter to many perf_event descriptors.
>
> You can find the source at
> http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=blob_plain;f=kvm/kvm_stat;hb=5bd5f131b50cb373ff4e2a3632c6dad00a1f0b55.
> All it needs are the kvm modules loaded; no need to actually run a
> guest. Run as root.
>
Does something like the below cure that?
I seem to remember C doesn't make any promises about the order of logic
statements, hence we need to explicitly pull out that try_module_get()
so that it evaluates after the rest of the conditions.
---
kernel/trace/trace_event_perf.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 000e6e8..35051f2 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -88,10 +88,11 @@ int perf_trace_init(struct perf_event *p_event)
mutex_lock(&event_mutex);
list_for_each_entry(tp_event, &ftrace_events, list) {
if (tp_event->event.type == event_id &&
- tp_event->class && tp_event->class->reg &&
- try_module_get(tp_event->mod)) {
- ret = perf_trace_event_init(tp_event, p_event);
- break;
+ tp_event->class && tp_event->class->reg) {
+ if (try_module_get(tp_event->mod)) {
+ ret = perf_trace_event_init(tp_event, p_event);
+ break;
+ }
}
}
mutex_unlock(&event_mutex);
@@ -138,6 +139,7 @@ void perf_trace_destroy(struct perf_event *p_event)
free_percpu(tp_event->perf_events);
tp_event->perf_events = NULL;
+ module_put(tp_event->mod);
if (!--total_ref_count) {
for (i = 0; i < 4; i++) {
next prev parent reply other threads:[~2010-09-01 9:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-01 8:42 ftrace/perf_event leak Avi Kivity
2010-09-01 9:04 ` Peter Zijlstra [this message]
2010-09-01 9:26 ` Avi Kivity
2010-09-01 9:35 ` Peter Zijlstra
2010-09-01 9:38 ` Li Zefan
2010-09-01 9:41 ` Peter Zijlstra
2010-09-01 10:38 ` Avi Kivity
2010-09-01 11:02 ` Peter Zijlstra
2010-09-01 11:07 ` Ingo Molnar
2010-09-01 12:15 ` Frederic Weisbecker
2010-09-01 13:59 ` Steven Rostedt
2010-09-01 17:32 ` Ingo Molnar
2010-09-02 1:20 ` Li Zefan
2010-09-09 19:45 ` [tip:perf/core] perf, trace: Fix module leak tip-bot for Li Zefan
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