1 #!/usr/bin/env python3
2 # SPDX-License-Identifier: GPL-2.0+
3 #
4 # This determines how many parallel tasks "mak
5 # not exposed via an special variables, reserv
6 # with PARALLELISM environment variable set, a
7 #
8 # https://www.gnu.org/software/make/manual/htm
9 from __future__ import print_function
10 import os, sys, errno
11 import subprocess
12
13 # Extract and prepare jobserver file descripto
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 --jobser
22 # so this handles all of them.
23 opts = [x for x in flags.split(" ") if
24
25 # Parse out R,W file descriptor number
26 # If the MAKEFLAGS variable contains m
27 # --jobserver-auth= option, the last o
28 fds = opts[-1].split("=", 1)[1]
29
30 # Starting with GNU Make 4.4, named pi
31 # Example argument: --jobserver-auth=f
32 _, _, path = fds.partition('fifo:')
33
34 if path:
35 reader = os.open(path, os.O_RD
36 writer = os.open(path, os.O_WR
37 else:
38 reader, writer = [int(x) for x
39 # Open a private copy of reade
40 # on an unexpecting process wi
41 reader = os.open("/proc/self/f
42 os.O_RDONLY |
43
44 # Read out as many jobserver slots as
45 while True:
46 try:
47 slot = os.read(reader,
48 jobs += slot
49 except (OSError, IOError) as e
50 if e.errno == errno.EW
51 # Stop at the
52 break
53 # If something went wr
54 if len(jobs):
55 os.write(write
56 raise e
57 # Add a bump for our caller's reserver
58 # to sit here blocked on our child.
59 claim = len(jobs) + 1
60 except (KeyError, IndexError, ValueError, OSEr
61 # Any missing environment strings or b
62 # not being parallel.
63 pass
64
65 # We can only claim parallelism if there was a
66 # "-jN" argument) and there were no other fail
67 # environment variable and let the child figur
68 if claim > 0:
69 os.environ['PARALLELISM'] = '%d' % (cl
70
71 rc = subprocess.call(sys.argv[1:])
72
73 # Return all the reserved slots.
74 if len(jobs):
75 os.write(writer, jobs)
76
77 sys.exit(rc)
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