perf record: Fix event fd races
The write call may set errno which is problematic if occurring in a function also setting errno. Save and restore errno around the write call. done_fd may be used after close, clear it as part of the close and check its validity in the signal handler. Suggested-by: <gthelen@google.com> Reviewed-by: Leo Yan <leo.yan@linaro.org> Signed-off-by: Ian Rogers <irogers@google.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Anand K Mistry <amistry@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: https://lore.kernel.org/r/20221024011024.462518-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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