[Intel-gfx] [PATCH 4/4] drm/i915/perf: Map OA buffer to user space for gen12 performance query

[Chris Wilson]

Quoting Umesh Nerlige Ramappa (2020-07-24 20:35:11)
> I agree, but strangely, with mmap sequence below, I don't see 
> i915_perf_release() called at all.  So destroy() is not called.
> 
> perf_fd = i915_perf_open_ioctl()
> mmap(..., perf_fd...)
> close(perf_fd)
> delay for a few seconds.
> 
> If I call munmap() after the close(), I see i915_perf_release() -> 
> destroy() -> unmap_mapping_range()

Hmm, vma->vm_file is pointing to the perf-fd. Ah, that's a big
difference to what I'm used to. So all the references are handled for
you by the correct vma->vm_file, and you don't need the
vm_open/vm_close, the kref or the closed. Sorry.
-Chris
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