Messages in this thread | | | Date | Fri, 17 Jul 2015 19:54:55 +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 19:40, 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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