Re: [PATCH] Rework the jobserver open logic

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Em Tue, 13 Jan 2026 13:42:16 -0700
Jonathan Corbet <corbet@lwn.net> escreveu:

> The parsing of jobserver options is done in a massive try: block that hides
> problems and (perhaps) bugs.  Split up that block and make the logic
> explicit by moving the initial parsing of MAKEFLAGS out of that block.  Add
> warnings in the places things can go wrong.
> 
> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
> ---
>  tools/lib/python/jobserver.py | 140 +++++++++++++++++++++-------------
>  1 file changed, 87 insertions(+), 53 deletions(-)
> 
> diff --git a/tools/lib/python/jobserver.py b/tools/lib/python/jobserver.py
> index 616411087725e..cd3bddb6e7560 100755
> --- a/tools/lib/python/jobserver.py
> +++ b/tools/lib/python/jobserver.py
> @@ -58,64 +58,98 @@ class JobserverExec:
>  
>          if self.is_open:
>              return
> -
> -        try:
> -            # Fetch the make environment options.
> -            flags = os.environ["MAKEFLAGS"]
> -            # Look for "--jobserver=R,W"
> -            # Note that GNU Make has used --jobserver-fds and --jobserver-auth
> -            # so this handles all of them.
> -            opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
> -
> -            # Parse out R,W file descriptor numbers and set them nonblocking.
> -            # If the MAKEFLAGS variable contains multiple instances of the
> -            # --jobserver-auth= option, the last one is relevant.
> -            fds = opts[-1].split("=", 1)[1]
> -
> -            # Starting with GNU Make 4.4, named pipes are used for reader
> -            # and writer.
> -            # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134
> -            _, _, path = fds.partition("fifo:")
> -
> -            if path:
> +        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:
> +            print('WARNING: unparseable option:', opts[-1])

On all prints, please use file=sys.stderr.

> +            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[5:]

Hmm... moving from partition() to startswith might be problematic...
are we sure that "fifo:" can't be in the middle of the string?

If so, instead of using "5" magic number, I would use len("fifo:")

Except for that, the changes looked OK on my eyes (but I didn't
test).

After addressing the above:

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Thanks,
Mauro