On 2015/7/17 19:40, Peter Zijlstra wrote:
On Fri, Jul 17, 2015 at 07:34:22PM +0800, Wangnan (F) wrote:
On 2015/7/17 19:21, Wangnan (F) wrote:
On 2015/7/17 19:06, Peter Zijlstra wrote:
On Fri, Jul 17, 2015 at 06:43:33PM +0800, kaixu xia wrote:
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e965cfa..c4e34b7 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8582,6 +8582,28 @@ void perf_event_delayed_put(struct task_struct
*task)
WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
}
+struct perf_event *perf_event_get(unsigned int fd)
+{
+ struct perf_event *event;
+ struct fd f;
+
+ f = fdget(fd);
+
+ if (!f.file)
+ return ERR_PTR(-EBADF);
+
+ if (f.file->f_op != &perf_fops) {
+ fdput(f);
+ return ERR_PTR(-EINVAL);
+ }
+
+ event = f.file->private_data;
+
+ fdput(f);
+
+ return event;
+}
And what is stopping userspace from closing those FDs while you're using
them?
Shall we put atomic_long_inc_not_zero() between fdget() and fdput()?
You pretty much _have_ to do that.
Thanks. In next version we will introduce a new function which do
oppsite thing to
perf_event_release_kernel() in perf/event/core.c, then fetch the event
before fdput.
Thank you.
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