Re: [PATCH 06/15] perf symbol: Fall back to fetching the vmlinux by build ID

[sashiko-bot@kernel.org]

> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> A profile recorded on a kernel that is no longer installed, e.g. one
> processed on another machine or after a kernel upgrade, cannot have its
> kernel symbols resolved: /proc/kallsyms does not match it and the
> build-id cache may carry only a kallsyms copy with zeroed addresses.
> Fetch the vmlinux keyed by the build ID recorded in perf.data, using
> debuginfod, as a last resort when no local source was found, honoring
> symbol_conf.ignore_vmlinux and ignore_vmlinux_buildid like the other
> vmlinux sources.
> 
> The fetch runs with dso->lock dropped, like dso__debuginfo(), and the
> file is loaded with the lock held again, only if no other thread got the
> symbols meanwhile (dso__has_symbols(), not dso__loaded(): the latter is
> set even for failed attempts).  With the lock dropped two threads can
> map the x86-64 entry trampolines at once, so that mapping is now
> idempotent.
> 
> Assisted-by: LLM
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260917155528.62607-1-acme@kernel.org?part=6