use -j; all make's in a recursive build cooperate to limit the total
number of jobs, using a token-passing scheme.
The current token passing algorithm is similar to the one implemented
by gmake; there is a single pipe which is inherited through the entire
process hierarchy; tokens are obtained by reading a byte from the
"read end" of the pipe, and are returned by writing them to the "write
end". This exact algorithm is likely to change in the future.
Implementation details:
- Use the new trace facility to allow measurement of the
effectiveness of different token-passing schemes
- Get a token in MakeStartJobs(), return it in Make_Update()
- Eliminate Job_Full() and the jobFull global since they are
redundant with token system.
- Add an "internal" -J option (to pass the token pipe fd's down to
submakes) and a -T option for tracing.
- Change how compatMake is forced so that -j means something when
inherited by submakes.
- When waiting for a token, poll the token-passing pipe as well as
the output pipes of existing jobs.
poll() for parallel make:
- Make the poll() code behave more like the select() code: sleep for
a bit waiting for output rather than busy-wait (eww).
- Install a no-op SIGCHLD handler so that poll/select wake up early
(with -1/EINTR) when a child exits.
- Change the default sleep time from 500ms to 5 seconds since we now
wake up promptly when a child exits.
try to open tfile many times, passing bad strings to mkstemp
2. remove extra semicolon after the MESSAGE macro
3. more error checking
4. be more careful about setting things to NULL after freeing.
5. fix a comment that does not apply anymore
arguments names on one function being swapped (by a previous author).
Do not do any duplicate suppression when a source list is created. Instead:
* OP_MADE protects against trying to make the source multiple times.
* A new OP_MARK flag is introduced to suppress duplicates while expanding
the .ALLSRC variable and .USE targets.
This turns the O(n^2) insertion into O(n) in most cases.
This is tested with a `make build' and some special test cases.
To avoid that, we now do ::[+?!]*= but the SysV = modifier can
conflict with any new modifier. At there are currently no Makefiles
in our tree that use ${FOO::=bar}
problems such as using modifiers on .for loop iterators derived from
local variables (eg .TARGET).
Unless the variable already exists in a global context, these assignments are
local to the current context (this is usually what is wanted).
is an empty list, use DEFSYSPATH.
The current behaviour may have been useful when DEFSYSMK was an
absolute path (hasn't been the case since 1996), but right now
make -m /no/such/dir will fail to find sys.mk and die.
These allow some very useful magic in the makefiles.
The comment in var.c describing their behaviour is mostly lifted
from ODE make, but the implementation of the modifiers themselves
is quite different (much simpler) due to divergence of our code base.
Firstly, we ignore getenv("PWD") if MAKEOBJDIRPREFIX is set so that we always
get the same value for .CURDIR regardless of how make was invoked.
Second, when executing a command we check if it is ${.MAKE} or ${.MAKE:T}
without a preceeding chdir, if so we insert a chdir(${.CURDIR}) so that
the Makefile will be found by the child make. Note that this behaviour is
dissabled if MAKEOBJDIRPREFIX is not set or if NOCHECKMAKECHDIR is set.
See the comments in main.c for more detail.
With these two changes, one can successfully build usr/src using MAKEOBJDIRPREFIX
allowing the src to be mounted from a CD-ROM.
sommerfeld