Em Thu, Jan 29, 2015 at 05:07:21PM +0900, Namhyung Kim escreveu:
> When libunwind tries to resolve callchains it needs to know the offset
> of .eh_frame_hdr or .debug_frame to access the dso. Since it calls
> dso__data_fd(), it'll try to grab dso->lock everytime for same
> information. So save it to dso_data struct and reuse it.
>
> Note that there's a window between dso__data_fd() and actual use of
> the fd. The fd could be closed by other threads to deal with the open
> file limit in dso cache code. But I think it's ok since in that case
> elf_section_offset() will return 0 so it'll be tried in next acess.
Thanks, applied after rewriting the changelog to read as:
---
perf callchain: Cache eh/debug frame offset for dwarf unwind
When libunwind tries to resolve callchains it needs to know the
offset of .eh_frame_hdr or .debug_frame to access the dso.
Since it will always return the same result for a given DSO, just
cache the result as an optimization.
---
- Arnaldo
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