Convert the code inside jobserver-exec to a class and properly document it. Using a class allows reusing the jobserver logic on other scripts. While the main code remains unchanged, being compatible with Python 2.6 and 3.0+, its coding style now follows a more modern standard, having tabs replaced by a 4-spaces indent, passing autopep8, black and pylint. The code now allows allows using a pythonic way to enter/exit a python code, e.g. it now supports: with JobserverExec() as jobserver: jobserver.run(sys.argv[1:]) With the new code, the __exit__() function should ensure that the jobserver slot will be closed at the end, even if something bad happens somewhere. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx> --- scripts/jobserver-exec | 218 ++++++++++++++++++++++++++++------------- 1 file changed, 151 insertions(+), 67 deletions(-) diff --git a/scripts/jobserver-exec b/scripts/jobserver-exec index 7eca035472d3..b386b1a845de 100755 --- a/scripts/jobserver-exec +++ b/scripts/jobserver-exec @@ -1,77 +1,161 @@ #!/usr/bin/env python3 # SPDX-License-Identifier: GPL-2.0+ # +# pylint: disable=C0103,C0209 +# # This determines how many parallel tasks "make" is expecting, as it is # not exposed via an special variables, reserves them all, runs a subprocess # with PARALLELISM environment variable set, and releases the jobs back again. # # https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver -from __future__ import print_function -import os, sys, errno + +""" +Interacts with the POSIX jobserver during the Kernel build time. + +A "normal" jobserver task, like the one initiated by a make subrocess would do: + + - open read/write file descriptors to communicate with the job server; + - ask for one slot by calling: + claim = os.read(reader, 1) + - when the job finshes, call: + os.write(writer, b"+") # os.write(writer, claim) + +Here, the goal is different: This script aims to get the remaining number +of slots available, using all of them to run a command which handle tasks in +parallel. To to that, it has a loop that ends only after there are no +slots left. It then increments the number by one, in order to allow a +call equivalent to make -j$((claim+1)), e.g. having a parent make creating +$claim child to do the actual work. + +The end goal here is to keep the total number of build tasks under the +limit established by the initial make -j$n_proc call. +""" + +import errno +import os import subprocess +import sys -# Extract and prepare jobserver file descriptors from environment. -claim = 0 -jobs = b"" -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. - # If the MAKEFLAGS variable contains multiple instances of the - # --jobserver-auth= option, the last one is relevant. - fds = opts[-1].split("=", 1)[1] - - # Starting with GNU Make 4.4, named pipes are used for reader and writer. - # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134 - _, _, path = fds.partition('fifo:') - - if path: - reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK) - writer = os.open(path, os.O_WRONLY) - else: - 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) - - # Read out as many jobserver slots as possible. - while True: - try: - slot = os.read(reader, 8) - jobs += slot - except (OSError, IOError) as e: - if e.errno == errno.EWOULDBLOCK: - # Stop at the end of the jobserver queue. - break - # If something went wrong, give back the jobs. - if len(jobs): - os.write(writer, jobs) - raise e - # Add a bump for our caller's reserveration, since we're just going - # to sit here blocked on our child. - claim = len(jobs) + 1 -except (KeyError, IndexError, ValueError, OSError, IOError) as e: - # Any missing environment strings or bad fds should result in just - # not being parallel. - pass - -# We can only claim parallelism if there was a jobserver (i.e. a top-level -# "-jN" argument) and there were no other failures. Otherwise leave out the -# environment variable and let the child figure out what is best. -if claim > 0: - os.environ['PARALLELISM'] = '%d' % (claim) - -rc = subprocess.call(sys.argv[1:]) - -# Return all the reserved slots. -if len(jobs): - os.write(writer, jobs) - -sys.exit(rc) + +class JobserverExec: + """ + Claim all slots from make using POSIX Jobserver. + + The main methods here are: + - open(): reserves all slots; + - close(): method returns all used slots back to make; + - run(): executes a command setting PARALLELISM=<available slots jobs + 1> + """ + + def __init__(self): + """Initialize internal vars""" + self.claim = 0 + self.jobs = b"" + self.reader = None + self.writer = None + self.is_open = False + + def open(self): + """Reserve all available slots to be claimed later on""" + + if self.is_open: + return + + 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. + # If the MAKEFLAGS variable contains multiple instances of the + # --jobserver-auth= option, the last one is relevant. + fds = opts[-1].split("=", 1)[1] + + # Starting with GNU Make 4.4, named pipes are used for reader + # and writer. + # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134 + _, _, path = fds.partition("fifo:") + + if path: + self.reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK) + self.writer = os.open(path, os.O_WRONLY) + else: + self.reader, self.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. + self.reader = os.open("/proc/self/fd/%d" % (self.reader), + os.O_RDONLY | os.O_NONBLOCK) + + # Read out as many jobserver slots as possible + while True: + try: + slot = os.read(self.reader, 8) + self.jobs += slot + except (OSError, IOError) as e: + if e.errno == errno.EWOULDBLOCK: + # Stop at the end of the jobserver queue. + break + # If something went wrong, give back the jobs. + if self.jobs: + os.write(self.writer, self.jobs) + raise e + + # Add a bump for our caller's reserveration, since we're just going + # to sit here blocked on our child. + self.claim = len(self.jobs) + 1 + + except (KeyError, IndexError, ValueError, OSError, IOError): + # Any missing environment strings or bad fds should result in just + # not being parallel. + self.claim = None + + self.is_open = True + + def close(self): + """Return all reserved slots to Jobserver""" + + if not self.is_open: + return + + # Return all the reserved slots. + if len(self.jobs): + os.write(self.writer, self.jobs) + + self.is_open = False + + def __enter__(self): + self.open() + return self + + def __exit__(self, exc_type, exc_value, exc_traceback): + self.close() + + def run(self, cmd): + """ + Run a command setting PARALLELISM env variable to the number of + available job slots (claim) + 1, e.g. it will reserve claim slots + to do the actual build work, plus one to monitor its childs. + """ + self.open() # Ensure that self.claim is set + + # We can only claim parallelism if there was a jobserver (i.e. a + # top-level "-jN" argument) and there were no other failures. Otherwise + # leave out the environment variable and let the child figure out what + # is best. + if self.claim: + os.environ["PARALLELISM"] = str(self.claim) + + return subprocess.call(cmd) + + +def main(): + """Main program""" + with JobserverExec() as jobserver: + jobserver.run(sys.argv[1:]) + + +if __name__ == "__main__": + main() -- 2.50.1
