mirror of
https://github.com/Fishwaldo/linux-bl808.git
synced 2025-04-01 03:44:08 +00:00
dffd011480
Setting non-blocking via a local copy of the jobserver file descriptor is safer than just assuming other reader processes with the same fd open are prepared for it to be non-blocking. Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Link: https://lore.kernel.org/lkml/44c01043-ab24-b4de-6544-e8efd153e27a@rasmusvillemoes.dk Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20191121205929.40371-3-keescook@chromium.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
59 lines
1.9 KiB
Python
Executable file
59 lines
1.9 KiB
Python
Executable file
#!/usr/bin/env python
|
|
# SPDX-License-Identifier: GPL-2.0+
|
|
#
|
|
# This determines how many parallel tasks "make" is expecting, as it is
|
|
# not exposed via an special variables.
|
|
# https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver
|
|
from __future__ import print_function
|
|
import os, sys, fcntl, errno
|
|
|
|
# Default parallelism is "1" unless overridden on the command-line.
|
|
default="1"
|
|
if len(sys.argv) > 1:
|
|
default=sys.argv[1]
|
|
|
|
# Extract and prepare jobserver file descriptors from envirnoment.
|
|
try:
|
|
# Fetch the make environment options.
|
|
flags = os.environ['MAKEFLAGS']
|
|
|
|
# Look for "--jobserver=R,W"
|
|
# Note that GNU Make has used --jobserver-fds and --jobserver-auth
|
|
# so this handles all of them.
|
|
opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
|
|
|
|
# Parse out R,W file descriptor numbers and set them nonblocking.
|
|
fds = opts[0].split("=", 1)[1]
|
|
reader, writer = [int(x) for x in fds.split(",", 1)]
|
|
# Open a private copy of reader to avoid setting nonblocking
|
|
# on an unexpecting process with the same reader fd.
|
|
reader = os.open("/proc/self/fd/%d" % (reader),
|
|
os.O_RDONLY | os.O_NONBLOCK)
|
|
except (KeyError, IndexError, ValueError, IOError, OSError) as e:
|
|
print(e, file=sys.stderr)
|
|
# Any missing environment strings or bad fds should result in just
|
|
# using the default specified parallelism.
|
|
print(default)
|
|
sys.exit(0)
|
|
|
|
# Read out as many jobserver slots as possible.
|
|
jobs = b""
|
|
while True:
|
|
try:
|
|
slot = os.read(reader, 1)
|
|
jobs += slot
|
|
except (OSError, IOError) as e:
|
|
if e.errno == errno.EWOULDBLOCK:
|
|
# Stop when reach the end of the jobserver queue.
|
|
break
|
|
raise e
|
|
# Return all the reserved slots.
|
|
os.write(writer, jobs)
|
|
|
|
# If the jobserver was (impossibly) full or communication failed, use default.
|
|
if len(jobs) < 1:
|
|
print(default)
|
|
sys.exit(0)
|
|
|
|
# Report available slots (with a bump for our caller's reserveration).
|
|
print(len(jobs) + 1)
|