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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 certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: rsa-pkcs1pad - Use akcipher_request_complete 2023-03-10 09:33:03 +01:00
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 gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring io_uring/uring_cmd: ensure that device supports IOPOLL 2023-03-17 08:50:14 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel watch_queue: fix IOC_WATCH_QUEUE_SET_SIZE alloc error paths 2023-03-17 08:50:30 +01:00
lib sbitmap: Try each queue to wake up at least one waiter 2023-03-10 09:34:34 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm memory tier: release the new_memtier in find_create_memory_tier() 2023-03-10 09:34:27 +01:00
net af_unix: fix struct pid leaks in OOB support 2023-03-17 08:50:28 +01:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-02-06 08:06:34 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-02-01 08:34:37 +01:00
scripts scripts: handle BrokenPipeError for python scripts 2023-03-17 08:50:31 +01:00
security ima: Align ima_file_mmap() parameters with mmap_file LSM hook 2023-03-10 09:34:15 +01:00
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 usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Register /dev/kvm as the _very_ last thing during initialization 2023-03-10 09:34:11 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS audit: update the mailing list in MAINTAINERS 2023-02-25 11:25:42 +01:00
Makefile Linux 6.1.19 2023-03-13 10:21:32 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.