fastannotate: remove support for flock() locking

fastannotate: remove support for flock() locking

We've seen enough weirdness in CI with flock for remotefilelog that
I'm now of the opinion we should just stop using flock() everywhere
until someone has a concrete need for the extra performance *and* a
way to only use it when safe (even if that's just default-to-off.)

Differential Revision: https://phab.mercurial-scm.org/D6861

--- a/hgext/fastannotate/__init__.py	Tue Sep 17 14:20:13 2019 -0400
+++ b/hgext/fastannotate/__init__.py	Tue Sep 17 14:22:22 2019 -0400
@@ -62,13 +62,6 @@
     # the server. (default: 10)
     clientfetchthreshold = 10
 
-    # use flock instead of the file existence lock
-    # flock may not work well on some network filesystems, but they avoid
-    # creating and deleting files frequently, which is faster when updating
-    # the annotate cache in batch. if you have issues with this option, set it
-    # to False. (default: True if flock is supported, False otherwise)
-    useflock = True
-
     # for "fctx" mode, always follow renames regardless of command line option.
     # this is a BC with the original command but will reduced the space needed
     # for annotate cache, and is useful for client-server setup since the
@@ -100,8 +93,6 @@
 #
 # * rename the config knob for updating the local cache from a remote server
 #
-# * move `flock` based locking to a common area
-#
 # * revise wireprotocol for sharing annotate files
 #
 # * figure out a sensible default for `mainbranch` (with the caveat
@@ -114,7 +105,6 @@
 
 from mercurial.i18n import _
 from mercurial import (
-    configitems,
     error as hgerror,
     localrepo,
     registrar,
@@ -122,7 +112,6 @@
 
 from . import (
     commands,
-    context,
     protocol,
 )
 
@@ -139,7 +128,6 @@
 
 configitem('fastannotate', 'modes', default=['fastannotate'])
 configitem('fastannotate', 'server', default=False)
-configitem('fastannotate', 'useflock', default=configitems.dynamicdefault)
 configitem('fastannotate', 'client', default=False)
 configitem('fastannotate', 'unfilteredrepo', default=True)
 configitem('fastannotate', 'defaultformat', default=['number'])
@@ -151,14 +139,6 @@
 configitem('fastannotate', 'serverbuildondemand', default=True)
 configitem('fastannotate', 'remotepath', default='default')
 
-def _flockavailable():
-    try:
-        import fcntl
-        fcntl.flock
-    except (AttributeError, ImportError):
-        return False
-    else:
-        return True
 
 def uisetup(ui):
     modes = set(ui.configlist('fastannotate', 'modes'))
@@ -180,9 +160,6 @@
     if ui.configbool('fastannotate', 'server'):
         protocol.serveruisetup(ui)
 
-    if ui.configbool('fastannotate', 'useflock', _flockavailable()):
-        context.pathhelper.lock = context.pathhelper._lockflock
-
 def extsetup(ui):
     # fastannotate has its own locking, without depending on repo lock
     # TODO: avoid mutating this unless the specific repo has it enabled

--- a/hgext/fastannotate/context.py	Tue Sep 17 14:20:13 2019 -0400
+++ b/hgext/fastannotate/context.py	Tue Sep 17 14:22:22 2019 -0400
@@ -759,21 +759,6 @@
     def lock(self):
         return lockmod.lock(self._repo.vfs, self._vfspath + '.lock')
 
-    @contextlib.contextmanager
-    def _lockflock(self):
-        """the same as 'lock' but use flock instead of lockmod.lock, to avoid
-        creating temporary symlinks."""
-        import fcntl
-        lockpath = self.linelogpath
-        util.makedirs(os.path.dirname(lockpath))
-        lockfd = os.open(lockpath, os.O_RDONLY | os.O_CREAT, 0o664)
-        fcntl.flock(lockfd, fcntl.LOCK_EX)
-        try:
-            yield
-        finally:
-            fcntl.flock(lockfd, fcntl.LOCK_UN)
-            os.close(lockfd)
-
     @property
     def revmappath(self):
         return self._repo.vfs.join(self._vfspath + '.m')