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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196#!/usr/bin/env python3# SPDX-License-Identifier: GPL-2.0+## pylint: disable=C0103,C0209##
"""Interacts with the POSIX jobserver during the Kernel build time.
A "normal" jobserver task, like the one initiated by a make subprocess 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 finishes, call::
os.write(writer, b"+") # os.write(writer, claim)
Here, the goal is different: This script aims to get the remaining numberof slots available, using all of them to run a command which handle tasks inparallel. To to that, it has a loop that ends only after there are noslots left. It then increments the number by one, in order to allow acall 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 thelimit established by the initial ``make -j$n_proc`` call.
See: https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver"""
import errnoimport osimport subprocessimport sys
def warn(text, *args): print(f'WARNING: {text}', *args, file = sys.stderr)
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 self.is_open = True # We only try once self.claim = None # # Check the make flags for "--jobserver=R,W" # Note that GNU Make has used --jobserver-fds and --jobserver-auth # so this handles all of them. # flags = os.environ.get('MAKEFLAGS', '') opts = [x for x in flags.split(" ") if x.startswith("--jobserver")] if not opts: return # # Separate out the provided file descriptors # split_opt = opts[-1].split('=', 1) if len(split_opt) != 2: warn('unparseable option:', opts[-1]) return fds = split_opt[1] # # As of GNU Make 4.4, we'll be looking for a named pipe # identified as fifo:path # if fds.startswith('fifo:'): path = fds[len('fifo:'):] try: self.reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK) self.writer = os.open(path, os.O_WRONLY) except (OSError, IOError): warn('unable to open jobserver pipe', path) return # # Otherwise look for integer file-descriptor numbers. # else: split_fds = fds.split(',') if len(split_fds) != 2: warn('malformed jobserver file descriptors:', fds) return try: self.reader = int(split_fds[0]) self.writer = int(split_fds[1]) except ValueError: warn('non-integer jobserver file-descriptors:', fds) return try: # # Open a private copy of reader to avoid setting nonblocking # on an unexpecting process with the same reader fd. # self.reader = os.open(f"/proc/self/fd/{self.reader}", os.O_RDONLY | os.O_NONBLOCK) except (IOError, OSError) as e: warn('Unable to reopen jobserver read-side pipe:', repr(e)) return # # OK, we have the channel to the job server; read out as many jobserver # slots as possible. # while True: try: slot = os.read(self.reader, 8) if not slot: # # Something went wrong. Clear self.jobs to avoid writing # weirdness back to the jobserver and give up. self.jobs = b"" warn("unexpected empty token from jobserver;" " possible invalid '--jobserver-auth=' setting") self.claim = None return except (OSError, IOError) as e: # # If there is nothing more to read then we are done. # if e.errno == errno.EWOULDBLOCK: break # # Anything else says that something went weird; give back # the jobs and give up. # if self.jobs: os.write(self.writer, self.jobs) self.claim = None warn('error reading from jobserver pipe', repr(e)) return self.jobs += slot # # 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
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, *args, **pwargs): """ 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 children. """ 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, *args, **pwargs)