tree 5f91990eb9bd1ec3a4637e8bd9961ac5ff32aff5
parent c27c6c8d8d61666b251790fe7d347871ee945d39
author Namhyung Kim <namhyung@kernel.org> 1418888215 +0900
committer Namhyung Kim <namhyung@kernel.org> 1419378163 +0900

perf callchain: Save 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 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.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>