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git.ipfire.org Git - thirdparty/linux.git/blob - scripts/jobserver-exec
2 # SPDX-License-Identifier: GPL-2.0+
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.
8 # https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver
9 from __future__
import print_function
13 # Extract and prepare jobserver file descriptors from environment.
17 # Fetch the make environment options.
18 flags
= os
.environ
['MAKEFLAGS']
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")]
25 # Parse out R,W file descriptor numbers and set them nonblocking.
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]
30 # Starting with GNU Make 4.4, named pipes are used for reader and writer.
31 # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134
32 _
, _
, path
= fds
.partition('fifo:')
35 reader
= os
.open(path
, os
.O_RDONLY | os
.O_NONBLOCK
)
36 writer
= os
.open(path
, os
.O_WRONLY
)
38 reader
, writer
= [int(x
) for x
in fds
.split(",", 1)]
39 # Open a private copy of reader to avoid setting nonblocking
40 # on an unexpecting process with the same reader fd.
41 reader
= os
.open("/proc/self/fd/%d" % (reader
),
42 os
.O_RDONLY | os
.O_NONBLOCK
)
44 # Read out as many jobserver slots as possible.
47 slot
= os
.read(reader
, 8)
49 except (OSError, IOError) as e
:
50 if e
.errno
== errno
.EWOULDBLOCK
:
51 # Stop at the end of the jobserver queue.
53 # If something went wrong, give back the jobs.
55 os
.write(writer
, jobs
)
57 # Add a bump for our caller's reserveration, since we're just going
58 # to sit here blocked on our child.
60 except (KeyError, IndexError, ValueError, OSError, IOError) as e
:
61 # Any missing environment strings or bad fds should result in just
65 # We can only claim parallelism if there was a jobserver (i.e. a top-level
66 # "-jN" argument) and there were no other failures. Otherwise leave out the
67 # environment variable and let the child figure out what is best.
69 os
.environ
['PARALLELISM'] = '%d' % (claim
)
71 rc
= subprocess
.call(sys
.argv
[1:])
73 # Return all the reserved slots.
75 os
.write(writer
, jobs
)