A whole bunch of cleanups to state.Lock.

Now t/curse passes again when parallelized (except for the countall
mismatch, since we haven't fixed the source of that problem yet).  At least
it's consistent now.

There's a bunch of stuff rearranged in here, but the actual important
problem was that we were doing unlink() on the lock fifo even if ENXIO,
which meant a reader could connect in between ENXIO and unlink(), and thus
never get notified of the disconnection.  This would cause the build to
randomly freeze.

clean.do

@@ -1,3 +1,3 @@
 redo t/clean
-rm -f t/hello t/[by]ellow t/*.o *~ .*~ */*~ */.*~ *.pyc t/CC t/LD
+rm -f *~ .*~ */*~ */.*~ *.pyc
 rm -rf .redo t/.redo

helpers.py

@@ -36,6 +36,7 @@ def mkdirp(d, mode=None):
 def log_(s):
     sys.stdout.flush()
     sys.stderr.write(s)
+    #sys.stderr.write('%d %s' % (os.getpid(), s))
     sys.stderr.flush()
 
 

jwack.py

@@ -81,6 +81,7 @@ def wait(want_token):
     rfds = _waitfds.keys()
     if _fds and want_token:
         rfds.append(_fds[0])
+    assert(rfds)
     r,w,x = select.select(rfds, [], [])
     _debug('_fds=%r; wfds=%r; readable: %r\n' % (_fds, _waitfds, r))
     for fd in r:
@@ -99,6 +100,7 @@ def wait(want_token):
                 pd.rv = os.WEXITSTATUS(rv)
             else:
                 pd.rv = -os.WTERMSIG(rv)
+            pd.donefunc(pd.name, pd.rv)
 
 
 def get_token(reason):
@@ -119,9 +121,13 @@ def get_token(reason):
     _debug('(%r) got a token (%r).\n' % (reason, b))
 
 
+def running():
+    return len(_waitfds)
+
+
 def wait_all():
     _debug("wait_all\n")
-    while _waitfds:
+    while running():
         _debug("wait_all: wait()\n")
         wait(want_token=0)
     _debug("wait_all: empty list\n")
@@ -134,7 +140,7 @@ def wait_all():
         if len(bb) != _toplevel-1:
             raise Exception('on exit: expected %d tokens; found only %d' 
                             % (_toplevel-1, len(b)))
-    _debug("wait_all: done\n")
+        os.write(_fds[1], bb)
 
 
 def force_return_tokens():
@@ -155,13 +161,17 @@ def _pre_job(r, w, pfn):
 
 
 class Job:
-    def __init__(self, name, pid):
+    def __init__(self, name, pid, donefunc):
         self.name = name
         self.pid = pid
         self.rv = None
+        self.donefunc = donefunc
+        
+    def __repr__(self):
+        return 'Job(%s,%d)' % (self.name, self.pid)
 
             
-def start_job(reason, jobfunc):
+def start_job(reason, jobfunc, donefunc):
     setup(1)
     get_token(reason)
     r,w = os.pipe()
@@ -180,6 +190,5 @@ def start_job(reason, jobfunc):
             os._exit(201)
     # else we're the parent process
     os.close(w)
-    pd = Job(reason, pid)
+    pd = Job(reason, pid, donefunc)
     _waitfds[r] = pd
-    return pd

redo.py

@@ -48,14 +48,12 @@ if is_root:
     # deliberately starts more than one redo on the same repository, it's
     # sort of ok.
     mkdirp('%s/.redo' % base)
-    for f in glob.glob('%s/.redo/lock^*' % base):
+    for f in glob.glob('%s/.redo/lock*' % base):
         os.unlink(f)
 
 
 class BuildError(Exception):
     pass
-class BuildLocked(Exception):
-    pass
 
 
 def _possible_do_files(t):
@@ -100,7 +98,6 @@ def _build(t):
         # which is undesirable since hello.c existed already.
         state.stamp(t)
         return  # success
-    state.unstamp(t)
     state.start(t)
     (dofile, basename, ext) = find_do_file(t)
     if not dofile:
@@ -145,7 +142,7 @@ def _build(t):
 
 def build(t):
     lock = state.Lock(t)
-    lock.lock()
+    lock.trylock()
     if not lock.owned:
         log('%s (locked...)\n' % relpath(t, vars.STARTDIR))
         os._exit(199)
@@ -160,34 +157,44 @@ def build(t):
 
 
 def main():
-    retcode = 0
-    locked = {}
-    waits = {}
+    retcode = [0]  # a list so that it can be reassigned from done()
     if vars.SHUFFLE:
         random.shuffle(targets)
+
+    locked = []
+
+    def done(t, rv):
+        if rv == 199:
+            locked.append(t)
+        elif rv:
+            err('%s: exit code was %r\n' % (t, rv))
+            retcode[0] = 1
+
     for t in targets:
         if os.path.exists('%s/all.do' % t):
             # t is a directory, but it has a default target
             t = '%s/all' % t
-        waits[t] = jwack.start_job(t, lambda: build(t))
+        tt = t
+        jwack.start_job(t, lambda: build(t), lambda t,rv: done(t,rv))
+    while locked or jwack.running():
         jwack.wait_all()
-    for t,pd in waits.items():
-        assert(pd.rv != None)
-        if pd.rv == 199:
-            # target was locked
-            locked[t] = 1
-        elif pd.rv:
-            err('%s: exit code was %r\n' % (t, pd.rv))
-            retcode = 1
-    for t in locked.keys():
-        lock = state.Lock(t)
-        lock.wait()
+        if locked:
+            t = locked.pop(0)
+            l = state.Lock(t)
+            while not l.owned:
+                l.wait()
+                l.trylock()
+            assert(l.owned)
             relp = relpath(t, vars.STARTDIR)
             log('%s (...unlocked!)\n' % relp)
             if state.stamped(t) == None:
                 err('%s: failed in another thread\n' % relp)
-            retcode = 2
-    return retcode
+                retcode[0] = 2
+                l.unlock()  # build() reacquires it
+                jwack.start_job(t, lambda: build(t), lambda t,rv: done(t,rv))
+            else:
+                l.unlock()
+    return retcode[0]
 
 
 if not vars.DEPTH:

state.py

@@ -70,6 +70,7 @@ def is_generated(t):
 
 
 def start(t):
+    unstamp(t)
     open(_sname('dep', t), 'w').close()
     open(_sname('gen', t), 'w').close()  # it's definitely a generated file
 
@@ -77,13 +78,14 @@ def start(t):
 class Lock:
     def __init__(self, t):
         self.lockname = _sname('lock', t)
+        self.tmpname = _sname('lock%d' % os.getpid(), t)
         self.owned = False
 
     def __del__(self):
         if self.owned:
             self.unlock()
 
-    def lock(self):
+    def trylock(self):
         try:
             os.mkfifo(self.lockname, 0600)
             self.owned = True
@@ -97,18 +99,22 @@ class Lock:
         if not self.owned:
             raise Exception("can't unlock %r - we don't own it" 
                             % self.lockname)
-        fd = None
+        # make sure no readers can connect
         try:
-            fd = os.open(self.lockname, os.O_WRONLY|os.O_NONBLOCK)
+            os.rename(self.lockname, self.tmpname)
+        except OSError, e:
+            if e.errno == errno.ENOENT: # 'make clean' might do this
+                self.owned = False
+                return
+        try:
+            # ping any connected readers
+            os.close(os.open(self.tmpname, os.O_WRONLY|os.O_NONBLOCK))
         except OSError, e:
             if e.errno == errno.ENXIO: # no readers open; that's ok
                 pass
-            elif e.errno == errno.ENOENT: # 'make clean' might do this
-                pass
             else:
                 raise
-        unlink(self.lockname)  # make sure no new readers can connect
-        if fd != None: os.close(fd)  # now unlock any existing readers
+        os.unlink(self.tmpname)
         self.owned = False
 
     def wait(self):
@@ -117,10 +123,8 @@ class Lock:
         try:
             # open() will finish only when a writer exists and does close()
             os.close(os.open(self.lockname, os.O_RDONLY))
-            #sys.stderr.write('lock %r waited ok\n' % self.lockname)
         except OSError, e:
             if e.errno == errno.ENOENT:
-                #sys.stderr.write('lock %r missing\n' % self.lockname)
                 pass  # it's not even unlocked or was unlocked earlier
             else:
                 raise

t/clean.do

@@ -1,2 +1,3 @@
 redo example/clean curse/clean
 rm -f c c.c c.c.c c.c.c.b c.c.c.b.b d
+rm -f hello [by]ellow *.o *~ .*~ CC LD