Messages in this thread | | | Date | Fri, 17 Jul 2015 19:34:22 +0800 | From | "Wangnan (F)" <> | Subject | Re: [RFC PATCH 3/6] bpf: Save the pointer to struct perf_event to map |
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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? > > Please check replace_map_with_perf_event(). Users can close the FDs, > but the perf > event structure will still valid because we increase its reference > count. It won't be > close until the map is released. We have test that case. > > Thank you. >
Shall we put atomic_long_inc_not_zero() between fdget() and fdput()?
Thank you.
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