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Masahiro Yamada 42d9fb7077 scripts: handle BrokenPipeError for python scripts 
[ Upstream commit 87c7ee67de ]

In the follow-up of commit fb3041d61f ("kbuild: fix SIGPIPE error
message for AR=gcc-ar and AR=llvm-ar"), Kees Cook pointed out that
tools should _not_ catch their own SIGPIPEs [1] [2].

Based on his feedback, LLVM was fixed [3].

However, Python's default behavior is to show noisy bracktrace when
SIGPIPE is sent. So, scripts written in Python are basically in the
same situation as the buggy llvm tools.

Example:

  $ make -s allnoconfig
  $ make -s allmodconfig
  $ scripts/diffconfig .config.old .config | head -n1
  -ALIX n
  Traceback (most recent call last):
    File "/home/masahiro/linux/scripts/diffconfig", line 132, in <module>
      main()
    File "/home/masahiro/linux/scripts/diffconfig", line 130, in main
      print_config("+", config, None, b[config])
    File "/home/masahiro/linux/scripts/diffconfig", line 64, in print_config
      print("+%s %s" % (config, new_value))
  BrokenPipeError: [Errno 32] Broken pipe

Python documentation [4] notes how to make scripts die immediately and
silently:

  """
  Piping output of your program to tools like head(1) will cause a
  SIGPIPE signal to be sent to your process when the receiver of its
  standard output closes early. This results in an exception like
  BrokenPipeError: [Errno 32] Broken pipe. To handle this case,
  wrap your entry point to catch this exception as follows:

    import os
    import sys

    def main():
        try:
            # simulate large output (your code replaces this loop)
            for x in range(10000):
                print("y")
            # flush output here to force SIGPIPE to be triggered
            # while inside this try block.
            sys.stdout.flush()
        except BrokenPipeError:
            # Python flushes standard streams on exit; redirect remaining output
            # to devnull to avoid another BrokenPipeError at shutdown
            devnull = os.open(os.devnull, os.O_WRONLY)
            os.dup2(devnull, sys.stdout.fileno())
            sys.exit(1)  # Python exits with error code 1 on EPIPE

    if __name__ == '__main__':
        main()

  Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
  BrokenPipeError. Doing that would cause your program to exit
  unexpectedly whenever any socket connection is interrupted while
  your program is still writing to it.
  """

Currently, tools/perf/scripts/python/intel-pt-events.py seems to be the
only script that fixes the issue that way.

tools/perf/scripts/python/compaction-times.py uses another approach
signal.signal(signal.SIGPIPE, signal.SIG_DFL) but the Python
documentation clearly says "Don't do it".

I cannot fix all Python scripts since there are so many.
I fixed some in the scripts/ directory.

[1]: https://lore.kernel.org/all/202211161056.1B9611A@keescook/
[2]: https://github.com/llvm/llvm-project/issues/59037
[3]: 4787efa380
[4]: https://docs.python.org/3/library/signal.html#note-on-sigpipe

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-03-17 08:50:31 +01:00
arch alpha: fix R_ALPHA_LITERAL reloc for large modules 2023-03-17 08:50:31 +01:00
block block: fix wrong mode for blkdev_put() from disk_scan_partitions() 2023-03-17 08:50:27 +01:00
certs
crypto
Documentation usb: gadget: uvc: Make bSourceID read/write 2023-03-11 13:55:38 +01:00
drivers macintosh: windfarm: Use unsigned type for 1-bit bitfields 2023-03-17 08:50:31 +01:00
fs ext4: Fix deadlock during directory rename 2023-03-17 08:50:29 +01:00
include PCI: Add SolidRun vendor ID 2023-03-17 08:50:31 +01:00
init
io_uring io_uring/uring_cmd: ensure that device supports IOPOLL 2023-03-17 08:50:14 +01:00
ipc
kernel watch_queue: fix IOC_WATCH_QUEUE_SET_SIZE alloc error paths 2023-03-17 08:50:30 +01:00
lib
LICENSES
mm
net af_unix: fix struct pid leaks in OOB support 2023-03-17 08:50:28 +01:00
rust
samples
scripts scripts: handle BrokenPipeError for python scripts 2023-03-17 08:50:31 +01:00
security
sound ASoC: mediatek: mt8195: add missing initialization 2023-03-11 13:55:31 +01:00
tools bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES 2023-03-17 08:50:26 +01:00
usr
virt
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.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
.rustfmt.toml
COPYING
CREDITS
Kbuild
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MAINTAINERS
Makefile Linux 6.1.19 2023-03-13 10:21:32 +01:00
README

README 

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.