From 7fb8e163bdfdc5ffb69b98f3f05ef0dbade4e677 Mon Sep 17 00:00:00 2001 From: Pete Wyckoff Date: Sun, 22 Apr 2012 16:30:58 -0400 Subject: [PATCH] git-remote-testgit: fix race when spawning fast-import Test "pushing to local repo" in t5800-remote-helpers can hang due to a race condition in git-remote-testgit. Fix it by setting stdin to unbuffered. On the writer side, "git push" invokes push_refs_with_export(), which sends to stdout the command "export\n" and immediately starts up "git fast-export". The latter writes its output stream to the same stdout. On the reader side, remote helper "git-remote-testgit" reads from stdin to get its next command. It uses getc() to read characters from libc up until \n. Libc has buffered a potentially much larger chunk of stdin. When it sees the "export\n" command, it forks "git fast-import" to read the stream. If fast-export finishes before git fast-import starts, the fast-export output can end up in libc's buffer in git-remote-testgit, rather than in git fast-import. The latter hangs indefinitely on a now-empty stdin. Signed-off-by: Pete Wyckoff Signed-off-by: Junio C Hamano --- git-remote-testgit.py | 7 +++++++ t/t5800-remote-helpers.sh | 13 +++++++++++++ 2 files changed, 20 insertions(+) diff --git a/git-remote-testgit.py b/git-remote-testgit.py index 3dc4851cf..5f3ebd244 100644 --- a/git-remote-testgit.py +++ b/git-remote-testgit.py @@ -22,6 +22,7 @@ except ImportError: _digest = sha.new import sys import os +import time sys.path.insert(0, os.getenv("GITPYTHONLIB",".")) from git_remote_helpers.util import die, debug, warn @@ -204,6 +205,11 @@ def read_one_line(repo): """Reads and processes one command. """ + sleepy = os.environ.get("GIT_REMOTE_TESTGIT_SLEEPY") + if sleepy: + debug("Sleeping %d sec before readline" % int(sleepy)) + time.sleep(int(sleepy)) + line = sys.stdin.readline() cmdline = line @@ -258,6 +264,7 @@ def main(args): more = True + sys.stdin = os.fdopen(sys.stdin.fileno(), 'r', 0) while (more): more = read_one_line(repo) diff --git a/t/t5800-remote-helpers.sh b/t/t5800-remote-helpers.sh index 1c62001fc..570233451 100755 --- a/t/t5800-remote-helpers.sh +++ b/t/t5800-remote-helpers.sh @@ -72,6 +72,19 @@ test_expect_success 'pushing to local repo' ' compare_refs localclone HEAD server HEAD ' +# Generally, skip this test. It demonstrates a now-fixed race in +# git-remote-testgit, but is too slow to leave in for general use. +: test_expect_success 'racily pushing to local repo' ' + test_when_finished "rm -rf server2 localclone2" && + cp -a server server2 && + git clone "testgit::${PWD}/server2" localclone2 && + (cd localclone2 && + echo content >>file && + git commit -a -m three && + GIT_REMOTE_TESTGIT_SLEEPY=2 git push) && + compare_refs localclone2 HEAD server2 HEAD +' + test_expect_success 'synch with changes from localclone' ' (cd clone && git pull) -- 2.26.2