projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| d8d2d382 | 1 | #!/usr/bin/env python3 |
| 51e46c7a KC |
2 | # SPDX-License-Identifier: GPL-2.0+ |
| 3 | # | |
| 4 | # This determines how many parallel tasks "make" is expecting, as it is | |
| 5 | # not exposed via an special variables, reserves them all, runs a subprocess | |
| 6 | # with PARALLELISM environment variable set, and releases the jobs back again. | |
| 7 | # | |
| 8 | # https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver | |
| 9 | from __future__ import print_function | |
| 10 | import os, sys, errno | |
| 11 | import subprocess | |
| 12 | ||
| 98a499a1 | 13 | # Extract and prepare jobserver file descriptors from environment. |
| 51e46c7a KC |
14 | claim = 0 |
| 15 | jobs = b"" | |
| 16 | try: | |
| 17 | # Fetch the make environment options. | |
| 18 | flags = os.environ['MAKEFLAGS'] | |
| 19 | ||
| 20 | # Look for "--jobserver=R,W" | |
| 21 | # Note that GNU Make has used --jobserver-fds and --jobserver-auth | |
| 22 | # so this handles all of them. | |
| 23 | opts = [x for x in flags.split(" ") if x.startswith("--jobserver")] | |
| 24 | ||
| 25 | # Parse out R,W file descriptor numbers and set them nonblocking. | |
| f8f4dc76 MY |
26 | # If the MAKEFLAGS variable contains multiple instances of the |
| 27 | # --jobserver-auth= option, the last one is relevant. | |
| 28 | fds = opts[-1].split("=", 1)[1] | |
| 51e46c7a KC |
29 | reader, writer = [int(x) for x in fds.split(",", 1)] |
| 30 | # Open a private copy of reader to avoid setting nonblocking | |
| 31 | # on an unexpecting process with the same reader fd. | |
| 32 | reader = os.open("/proc/self/fd/%d" % (reader), | |
| 33 | os.O_RDONLY | os.O_NONBLOCK) | |
| 34 | ||
| 35 | # Read out as many jobserver slots as possible. | |
| 36 | while True: | |
| 37 | try: | |
| 38 | slot = os.read(reader, 8) | |
| 39 | jobs += slot | |
| 40 | except (OSError, IOError) as e: | |
| 41 | if e.errno == errno.EWOULDBLOCK: | |
| 42 | # Stop at the end of the jobserver queue. | |
| 43 | break | |
| 44 | # If something went wrong, give back the jobs. | |
| 45 | if len(jobs): | |
| 46 | os.write(writer, jobs) | |
| 47 | raise e | |
| 48 | # Add a bump for our caller's reserveration, since we're just going | |
| 49 | # to sit here blocked on our child. | |
| 50 | claim = len(jobs) + 1 | |
| 51 | except (KeyError, IndexError, ValueError, OSError, IOError) as e: | |
| 52 | # Any missing environment strings or bad fds should result in just | |
| 53 | # not being parallel. | |
| 54 | pass | |
| 55 | ||
| 56 | # We can only claim parallelism if there was a jobserver (i.e. a top-level | |
| 57 | # "-jN" argument) and there were no other failures. Otherwise leave out the | |
| 58 | # environment variable and let the child figure out what is best. | |
| 59 | if claim > 0: | |
| 60 | os.environ['PARALLELISM'] = '%d' % (claim) | |
| 61 | ||
| 62 | rc = subprocess.call(sys.argv[1:]) | |
| 63 | ||
| 64 | # Return all the reserved slots. | |
| 65 | if len(jobs): | |
| 66 | os.write(writer, jobs) | |
| 67 | ||
| 68 | sys.exit(rc) |