1 #!/usr/bin/env python3 1 #!/usr/bin/env python3
2 # SPDX-License-Identifier: GPL-2.0+ 2 # SPDX-License-Identifier: GPL-2.0+
3 # 3 #
4 # This determines how many parallel tasks "mak 4 # This determines how many parallel tasks "make" is expecting, as it is
5 # not exposed via an special variables, reserv 5 # not exposed via an special variables, reserves them all, runs a subprocess
6 # with PARALLELISM environment variable set, a 6 # with PARALLELISM environment variable set, and releases the jobs back again.
7 # 7 #
8 # https://www.gnu.org/software/make/manual/htm 8 # https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver
9 from __future__ import print_function 9 from __future__ import print_function
10 import os, sys, errno 10 import os, sys, errno
11 import subprocess 11 import subprocess
12 12
13 # Extract and prepare jobserver file descripto 13 # Extract and prepare jobserver file descriptors from environment.
14 claim = 0 14 claim = 0
15 jobs = b"" 15 jobs = b""
16 try: 16 try:
17 # Fetch the make environment options. 17 # Fetch the make environment options.
18 flags = os.environ['MAKEFLAGS'] 18 flags = os.environ['MAKEFLAGS']
19 19
20 # Look for "--jobserver=R,W" 20 # Look for "--jobserver=R,W"
21 # Note that GNU Make has used --jobser 21 # Note that GNU Make has used --jobserver-fds and --jobserver-auth
22 # so this handles all of them. 22 # so this handles all of them.
23 opts = [x for x in flags.split(" ") if 23 opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
24 24
25 # Parse out R,W file descriptor number 25 # Parse out R,W file descriptor numbers and set them nonblocking.
26 # If the MAKEFLAGS variable contains m 26 # If the MAKEFLAGS variable contains multiple instances of the
27 # --jobserver-auth= option, the last o 27 # --jobserver-auth= option, the last one is relevant.
28 fds = opts[-1].split("=", 1)[1] 28 fds = opts[-1].split("=", 1)[1]
29 29
30 # Starting with GNU Make 4.4, named pi 30 # Starting with GNU Make 4.4, named pipes are used for reader and writer.
31 # Example argument: --jobserver-auth=f 31 # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134
32 _, _, path = fds.partition('fifo:') 32 _, _, path = fds.partition('fifo:')
33 33
34 if path: 34 if path:
35 reader = os.open(path, os.O_RD 35 reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
36 writer = os.open(path, os.O_WR 36 writer = os.open(path, os.O_WRONLY)
37 else: 37 else:
38 reader, writer = [int(x) for x 38 reader, writer = [int(x) for x in fds.split(",", 1)]
39 # Open a private copy of reade 39 # Open a private copy of reader to avoid setting nonblocking
40 # on an unexpecting process wi 40 # on an unexpecting process with the same reader fd.
41 reader = os.open("/proc/self/f 41 reader = os.open("/proc/self/fd/%d" % (reader),
42 os.O_RDONLY | 42 os.O_RDONLY | os.O_NONBLOCK)
43 43
44 # Read out as many jobserver slots as 44 # Read out as many jobserver slots as possible.
45 while True: 45 while True:
46 try: 46 try:
47 slot = os.read(reader, 47 slot = os.read(reader, 8)
48 jobs += slot 48 jobs += slot
49 except (OSError, IOError) as e 49 except (OSError, IOError) as e:
50 if e.errno == errno.EW 50 if e.errno == errno.EWOULDBLOCK:
51 # Stop at the 51 # Stop at the end of the jobserver queue.
52 break 52 break
53 # If something went wr 53 # If something went wrong, give back the jobs.
54 if len(jobs): 54 if len(jobs):
55 os.write(write 55 os.write(writer, jobs)
56 raise e 56 raise e
57 # Add a bump for our caller's reserver 57 # Add a bump for our caller's reserveration, since we're just going
58 # to sit here blocked on our child. 58 # to sit here blocked on our child.
59 claim = len(jobs) + 1 59 claim = len(jobs) + 1
60 except (KeyError, IndexError, ValueError, OSEr 60 except (KeyError, IndexError, ValueError, OSError, IOError) as e:
61 # Any missing environment strings or b 61 # Any missing environment strings or bad fds should result in just
62 # not being parallel. 62 # not being parallel.
63 pass 63 pass
64 64
65 # We can only claim parallelism if there was a 65 # We can only claim parallelism if there was a jobserver (i.e. a top-level
66 # "-jN" argument) and there were no other fail 66 # "-jN" argument) and there were no other failures. Otherwise leave out the
67 # environment variable and let the child figur 67 # environment variable and let the child figure out what is best.
68 if claim > 0: 68 if claim > 0:
69 os.environ['PARALLELISM'] = '%d' % (cl 69 os.environ['PARALLELISM'] = '%d' % (claim)
70 70
71 rc = subprocess.call(sys.argv[1:]) 71 rc = subprocess.call(sys.argv[1:])
72 72
73 # Return all the reserved slots. 73 # Return all the reserved slots.
74 if len(jobs): 74 if len(jobs):
75 os.write(writer, jobs) 75 os.write(writer, jobs)
76 76
77 sys.exit(rc) 77 sys.exit(rc)
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