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Sometimes it needs to save the perf inject data to a file for debugging. But normally it assumes the same format for input and output, so the end result cannot be used due to a broken format. # perf record -a -o - sleep 1 | perf inject -b -o my.data # perf report -i my.data --stdio 0x208 [0]: failed to process type: 0 [Invalid argument] Error: failed to process sample # To display the perf.data header info, please use --header/--header-only options. # In this case, it thought the data has a regular file header since the output is not a pipe. But actually it doesn't have one and has a pipe file header. At the end of the session, it tries to rewrite the regular file header with updated features and it overwrites the data just follows the pipe header. Fix it by checking either the input and the output is a pipe. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Acked-by: Jiri Olsa <jolsa@redhat.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lore.kernel.org/lkml/20210719223153.1618812-4-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.