makedocbook: Add explicit locking for PLY parser table generation

Drop 'makedocbook --cache' (any dependency on the man-cache rule which
invokes that was dropped by the non-recursive make changes)

Instead, add some explicit locking which prevents processes colliding
over the file containing generated python code for the parser table.

2 files changed, 11 insertions, 10 deletions

diff --git a/newlib/doc/Makefile.inc b/newlib/doc/Makefile.inc
index 630681c88..d2c26a13b 100644
--- a/newlib/doc/Makefile.inc
+++ b/newlib/doc/Makefile.inc
@@ -14,11 +14,6 @@ doc/makedoc.o: doc/makedoc.c
 	$(MKDIR_P) doc
 	$(CC_FOR_BUILD) -g $(CFLAGS_FOR_BUILD) -o $@ -c $<
 
-man-cache:
-	${srcdir}/doc/makedocbook.py --cache
-
-PHONY += man-cache
-
 #
 # Subdir documentation rules.
 #
diff --git a/newlib/doc/makedocbook.py b/newlib/doc/makedocbook.py
index 66481a672..4e83ab63a 100755
--- a/newlib/doc/makedocbook.py
+++ b/newlib/doc/makedocbook.py
@@ -22,7 +22,9 @@
 
 from __future__ import print_function
 
+import fcntl
 import sys
+import os
 import re
 from optparse import OptionParser
 import lxml.etree
@@ -796,7 +798,15 @@ def p_error(t):
     print('parse error at line %d, token %s, next token %s' % (t.lineno, t, parser.token()), file=sys.stderr)
     exit(1)
 
-parser = yacc.yacc(start='input')
+# protect creating the parser with a lockfile, so that when multiple processes
+# are running this script simultaneously, we don't get one of them generating a
+# parsetab.py file, while another one attempts to read it...
+#
+# see also https://github.com/dabeaz/ply/pull/184
+with open(os.path.join(os.path.dirname(__file__), 'parsetab.lock'), 'w+') as lockfile:
+    fcntl.flock(lockfile.fileno(), fcntl.LOCK_EX)
+    parser = yacc.yacc(start='input')
+    fcntl.flock(lockfile.fileno(), fcntl.LOCK_UN)
 
 #
 #
@@ -829,12 +839,8 @@ def main(file):
 if __name__ == '__main__' :
     options = OptionParser()
     options.add_option('-v', '--verbose', action='count', dest = 'verbose', default = 0)
-    options.add_option('-c', '--cache', action='store_true', dest = 'cache', help="just ensure PLY cache is up to date")
     (opts, args) = options.parse_args()
 
-    if opts.cache:
-        sys.exit()
-
     verbose = opts.verbose
 
     if len(args) > 0: