Re: [PATCH 04/16] perf, mmap: Factor out perf_get_fd()

Robert Richter
2014-04-29T15:34:09Z

On 25.04.14 16:52:05, Peter Zijlstra wrote:
> But no, I don't think that helps, its still true that the moment you get
> a fd another thread can immediately close(). That would drop the last
> ref and free it, meanwhile perf_event_open() is happily poking at it.
>
> Now I think you could cure this by adding an extra ref before calling
> your perf_get_fd() and dropping that extra ref at the end, where we used
> to have fd_install().

Yes, right. I have a solution now which increments the event's ref
count before creating the file descriptor using try_get_event()/
put_event().

The patch also does not remove get_unused_fd_flags() and the err_fd
error handler.

Have an update already of a rebase version but still need to test it.

Would it be ok to split the patch set and send in a first step only
the first 4 patches that refactor the perf mmap code?

Thanks,

-Robert