apenwarr-redo/builder.py
Avery Pennarun 52236a3aed builder.py: don't spin while fighting for a file lock.
If we end up in builder phase 2, where we might need to
build stuff that was previously locked by someone else,
we will need to obtain a job token *and* the lock at the
same time in order to continue.  To prevent deadlocks,
we don't wait synchronously for one lock while holding the
other.

If several instances are fighting over the same lock and
there are insufficient job tokens for everyone, timing
could cause them to fight for a long time.  This seems
to happen a lot in freebsd for some reason.  To be a good
citizen, sleep for a while after each loop iteration.
This should ensure that eventually, most of the fighting
instances will be asleep by the time the next one tries to
grab the token, thus breaking the deadlock.
2018-10-29 07:31:28 +00:00

418 lines
15 KiB
Python

import sys, os, errno, random, stat, signal, time
import vars, jwack, state
from helpers import unlink, close_on_exec, join
from log import log, log_, debug, debug2, err, warn
def _default_do_files(filename):
l = filename.split('.')
for i in range(1,len(l)+1):
basename = join('.', l[:i])
ext = join('.', l[i:])
if ext: ext = '.' + ext
yield ("default%s.do" % ext), basename, ext
def possible_do_files(t):
dirname,filename = os.path.split(t)
yield (os.path.join(vars.BASE, dirname), "%s.do" % filename,
'', filename, '')
# It's important to try every possibility in a directory before resorting
# to a parent directory. Think about nested projects: I don't want
# ../../default.o.do to take precedence over ../default.do, because
# the former one might just be an artifact of someone embedding my project
# into theirs as a subdir. When they do, my rules should still be used
# for building my project in *all* cases.
t = os.path.normpath(os.path.join(vars.BASE, t))
dirname,filename = os.path.split(t)
dirbits = dirname.split('/')
for i in range(len(dirbits), -1, -1):
basedir = join('/', dirbits[:i])
subdir = join('/', dirbits[i:])
for dofile,basename,ext in _default_do_files(filename):
yield (basedir, dofile,
subdir, os.path.join(subdir, basename), ext)
def find_do_file(f):
for dodir,dofile,basedir,basename,ext in possible_do_files(f.name):
dopath = os.path.join(dodir, dofile)
debug2('%s: %s:%s ?\n' % (f.name, dodir, dofile))
if os.path.exists(dopath):
f.add_dep('m', dopath)
return dodir,dofile,basedir,basename,ext
else:
f.add_dep('c', dopath)
return None,None,None,None,None
def _nice(t):
return state.relpath(t, vars.STARTDIR)
def _try_stat(filename):
try:
return os.lstat(filename)
except OSError, e:
if e.errno == errno.ENOENT:
return None
else:
raise
class ImmediateReturn(Exception):
def __init__(self, rv):
Exception.__init__(self, "immediate return with exit code %d" % rv)
self.rv = rv
class BuildJob:
def __init__(self, t, sf, lock, shouldbuildfunc, donefunc):
self.t = t # original target name, not relative to vars.BASE
self.sf = sf
tmpbase = t
while not os.path.isdir(os.path.dirname(tmpbase) or '.'):
ofs = tmpbase.rfind('/')
assert(ofs >= 0)
tmpbase = tmpbase[:ofs] + '__' + tmpbase[ofs+1:]
self.tmpname1 = '%s.redo1.tmp' % tmpbase
self.tmpname2 = '%s.redo2.tmp' % tmpbase
self.lock = lock
self.shouldbuildfunc = shouldbuildfunc
self.donefunc = donefunc
self.before_t = _try_stat(self.t)
def start(self):
assert(self.lock.owned)
try:
dirty = self.shouldbuildfunc(self.t)
if not dirty:
# target doesn't need to be built; skip the whole task
return self._after2(0)
except ImmediateReturn, e:
return self._after2(e.rv)
if vars.NO_OOB or dirty == True:
self._start_do()
else:
self._start_unlocked(dirty)
def _start_do(self):
assert(self.lock.owned)
t = self.t
sf = self.sf
newstamp = sf.read_stamp()
if (sf.is_generated and
newstamp != state.STAMP_MISSING and
(sf.stamp != newstamp or sf.is_override)):
state.warn_override(_nice(t))
if not sf.is_override:
warn('%s - old: %r\n' % (_nice(t), sf.stamp))
warn('%s - new: %r\n' % (_nice(t), newstamp))
sf.set_override()
sf.set_checked()
sf.save()
return self._after2(0)
if (os.path.exists(t) and not os.path.isdir(t + '/.')
and not sf.is_generated):
# an existing source file that was not generated by us.
# This step is mentioned by djb in his notes.
# For example, a rule called default.c.do could be used to try
# to produce hello.c, but we don't want that to happen if
# hello.c was created by the end user.
debug2("-- static (%r)\n" % t)
sf.set_static()
sf.save()
return self._after2(0)
sf.zap_deps1()
(dodir, dofile, basedir, basename, ext) = find_do_file(sf)
if not dofile:
if os.path.exists(t):
sf.set_static()
sf.save()
return self._after2(0)
else:
err('no rule to make %r\n' % t)
return self._after2(1)
unlink(self.tmpname1)
unlink(self.tmpname2)
ffd = os.open(self.tmpname1, os.O_CREAT|os.O_RDWR|os.O_EXCL, 0666)
close_on_exec(ffd, True)
self.f = os.fdopen(ffd, 'w+')
# this will run in the dofile's directory, so use only basenames here
arg1 = basename + ext # target name (including extension)
arg2 = basename # target name (without extension)
argv = ['sh', '-e',
dofile,
arg1,
arg2,
# temp output file name
state.relpath(os.path.abspath(self.tmpname2), dodir),
]
if vars.VERBOSE: argv[1] += 'v'
if vars.XTRACE: argv[1] += 'x'
if vars.VERBOSE or vars.XTRACE: log_('\n')
firstline = open(os.path.join(dodir, dofile)).readline().strip()
if firstline.startswith('#!/'):
argv[0:2] = firstline[2:].split(' ')
log('%s\n' % _nice(t))
self.dodir = dodir
self.basename = basename
self.ext = ext
self.argv = argv
sf.is_generated = True
sf.save()
dof = state.File(name=os.path.join(dodir, dofile))
dof.set_static()
dof.save()
state.commit()
jwack.start_job(t, self._do_subproc, self._after)
def _start_unlocked(self, dirty):
# out-of-band redo of some sub-objects. This happens when we're not
# quite sure if t needs to be built or not (because some children
# look dirty, but might turn out to be clean thanks to checksums).
# We have to call redo-unlocked to figure it all out.
#
# Note: redo-unlocked will handle all the updating of sf, so we
# don't have to do it here, nor call _after1. However, we have to
# hold onto the lock because otherwise we would introduce a race
# condition; that's why it's called redo-unlocked, because it doesn't
# grab a lock.
argv = ['redo-unlocked', self.sf.name] + [d.name for d in dirty]
log('(%s)\n' % _nice(self.t))
state.commit()
def run():
os.chdir(vars.BASE)
os.environ['REDO_DEPTH'] = vars.DEPTH + ' '
signal.signal(signal.SIGPIPE, signal.SIG_DFL) # python ignores SIGPIPE
os.execvp(argv[0], argv)
assert(0)
# returns only if there's an exception
def after(t, rv):
return self._after2(rv)
jwack.start_job(self.t, run, after)
def _do_subproc(self):
# careful: REDO_PWD was the PWD relative to the STARTPATH at the time
# we *started* building the current target; but that target ran
# redo-ifchange, and it might have done it from a different directory
# than we started it in. So os.getcwd() might be != REDO_PWD right
# now.
assert(state.is_flushed())
dn = self.dodir
newp = os.path.realpath(dn)
os.environ['REDO_PWD'] = state.relpath(newp, vars.STARTDIR)
os.environ['REDO_TARGET'] = self.basename + self.ext
os.environ['REDO_DEPTH'] = vars.DEPTH + ' '
vars.add_lock(str(self.lock.fid))
if dn:
os.chdir(dn)
os.dup2(self.f.fileno(), 1)
os.close(self.f.fileno())
close_on_exec(1, False)
signal.signal(signal.SIGPIPE, signal.SIG_DFL) # python ignores SIGPIPE
if vars.VERBOSE or vars.XTRACE: log_('* %s\n' % ' '.join(self.argv))
os.execvp(self.argv[0], self.argv)
assert(0)
# returns only if there's an exception
def _after(self, t, rv):
try:
state.check_sane()
rv = self._after1(t, rv)
state.commit()
finally:
self._after2(rv)
def _after1(self, t, rv):
f = self.f
before_t = self.before_t
after_t = _try_stat(t)
st1 = os.fstat(f.fileno())
st2 = _try_stat(self.tmpname2)
if (after_t and
(not before_t or before_t.st_mtime != after_t.st_mtime) and
not stat.S_ISDIR(after_t.st_mode)):
err('%s modified %s directly!\n' % (self.argv[2], t))
err('...you should update $3 (a temp file) or stdout, not $1.\n')
rv = 206
elif st2 and st1.st_size > 0:
err('%s wrote to stdout *and* created $3.\n' % self.argv[2])
err('...you should write status messages to stderr, not stdout.\n')
rv = 207
if rv==0:
if st2:
try:
os.rename(self.tmpname2, t)
except OSError, e:
dnt = os.path.dirname(t)
if not os.path.exists(dnt):
err('%s: target dir %r does not exist!\n' % (t, dnt))
else:
err('%s: rename %s: %s\n' % (t, self.tmpname2, e))
raise
os.unlink(self.tmpname1)
elif st1.st_size > 0:
try:
os.rename(self.tmpname1, t)
except OSError, e:
if e.errno == errno.ENOENT:
unlink(t)
else:
err('%s: can\'t save stdout to %r: %s\n' %
(self.argv[2], t, e.strerror))
rv = 1000
if st2:
os.unlink(self.tmpname2)
else: # no output generated at all; that's ok
unlink(self.tmpname1)
unlink(t)
sf = self.sf
sf.refresh()
sf.is_generated = True
sf.is_override = False
if sf.is_checked() or sf.is_changed():
# it got checked during the run; someone ran redo-stamp.
# update_stamp would call set_changed(); we don't want that
sf.stamp = sf.read_stamp()
else:
sf.csum = None
sf.update_stamp()
sf.set_changed()
else:
unlink(self.tmpname1)
unlink(self.tmpname2)
sf = self.sf
sf.set_failed()
sf.zap_deps2()
sf.save()
f.close()
if rv != 0:
err('%s: exit code %r\n' % (_nice(t),rv))
else:
if vars.VERBOSE or vars.XTRACE or vars.DEBUG:
log('%s (done)\n\n' % _nice(t))
return rv
def _after2(self, rv):
try:
self.donefunc(self.t, rv)
assert(self.lock.owned)
finally:
self.lock.unlock()
def main(targets, shouldbuildfunc):
retcode = [0] # a list so that it can be reassigned from done()
if vars.SHUFFLE:
import random
random.shuffle(targets)
locked = []
def done(t, rv):
if rv:
retcode[0] = 1
# In the first cycle, we just build as much as we can without worrying
# about any lock contention. If someone else has it locked, we move on.
seen = {}
lock = None
for t in targets:
assert(state.is_flushed())
if t in seen:
continue
seen[t] = 1
if not jwack.has_token():
state.commit()
jwack.get_token(t)
if retcode[0] and not vars.KEEP_GOING:
break
if not state.check_sane():
err('.redo directory disappeared; cannot continue.\n')
retcode[0] = 205
break
f = state.File(name=t)
lock = state.Lock(f.id)
if vars.UNLOCKED:
lock.owned = True
else:
lock.trylock()
if not lock.owned:
if vars.DEBUG_LOCKS:
log('%s (locked...)\n' % _nice(t))
locked.append((f.id,t))
else:
# We had to create f before we had a lock, because we need f.id
# to make the lock. But someone may have updated the state
# between then and now.
# FIXME: separate obtaining the fid from creating the File.
# FIXME: maybe integrate locking into the File object?
f.refresh()
BuildJob(t, f, lock, shouldbuildfunc, done).start()
state.commit()
assert(state.is_flushed())
lock = None
del lock
# Now we've built all the "easy" ones. Go back and just wait on the
# remaining ones one by one. There's no reason to do it any more
# efficiently, because if these targets were previously locked, that
# means someone else was building them; thus, we probably won't need to
# do anything. The only exception is if we're invoked as redo instead
# of redo-ifchange; then we have to redo it even if someone else already
# did. But that should be rare.
while locked or jwack.running():
state.commit()
jwack.wait_all()
# at this point, we don't have any children holding any tokens, so
# it's okay to block below.
if retcode[0] and not vars.KEEP_GOING:
break
if locked:
if not state.check_sane():
err('.redo directory disappeared; cannot continue.\n')
retcode[0] = 205
break
fid,t = locked.pop(0)
lock = state.Lock(fid)
backoff = 0.01
lock.trylock()
while not lock.owned:
# Don't spin with 100% CPU while we fight for the lock.
import random
time.sleep(random.random() * min(backoff, 1.0))
backoff *= 2
if vars.DEBUG_LOCKS:
warn('%s (WAITING)\n' % _nice(t))
# this sequence looks a little silly, but the idea is to
# give up our personal token while we wait for the lock to
# be released; but we should never run get_token() while
# holding a lock, or we could cause deadlocks.
jwack.release_mine()
try:
lock.waitlock()
except state.CyclicDependencyError:
err('cyclic dependency while building %s\n' % _nice(t))
jwack.get_token(t)
retcode[0] = 208
return retcode[0]
lock.unlock()
jwack.get_token(t)
lock.trylock()
assert(lock.owned)
if vars.DEBUG_LOCKS:
log('%s (...unlocked!)\n' % _nice(t))
if state.File(name=t).is_failed():
err('%s: failed in another thread\n' % _nice(t))
retcode[0] = 2
lock.unlock()
else:
BuildJob(t, state.File(id=fid), lock,
shouldbuildfunc, done).start()
lock = None
state.commit()
return retcode[0]