Re: [PATCH v4 1/3] perf libdw: Fix Dwfl discovery with split files

[sashiko-bot@kernel.org]

> dso__libdw_dwfl() opens the Dwfl with dso__long_name(), the file the
> samples came from. When the debug information lives in a separate file,
> symbol loading finds it and records it as the dso's symsrc filename, but
> the Dwfl still refers to the original file, so libdw has no DWARF to
> resolve addresses against.
> 
> Open the Dwfl with the symsrc filename when one is known and fall back
> to the long name when it isn't.
> 
> The symsrc file is found while symbols are loaded, which can happen
> after the Dwfl has been created and cached, so drop the cached Dwfl and
> the addr2line cache built from it when the symsrc filename is set.
> That teardown can run while another thread is using the cache, so take
> the dso lock across both the teardown and the Dwfl accessors, and
> re-read dso__symsrc_filename() under the dso lock in libbfd__addr2line()
> and cmd__addr2line() to prevent a TOCTOU race with cache invalidation.
> 
> Fixes: b7a2b011e962 ("perf powerpc: Unify the skip-callchain-idx libdw with that for addr2line")
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260917050450.703018-1-irogers@google.com?part=1