From 7bfa5bd64cd0fa4a7a76f996034a40e9df91b1be Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Tue, 18 May 2021 22:48:24 +0200 Subject: [PATCH] git_config_set_multivar_in_file_gently(): add a lock timeout In particular when multiple processes want to write to the config simultaneously, it would come in handy to not fail immediately when another process locked the config, but to gently try again. This will help with Scalar's functional test suite which wants to register multiple repositories for maintenance semi-simultaneously. As not all code paths calling this function read the config (e.g. `git config`), we have to read the config setting via `git_config_get_ulong()`. Signed-off-by: Johannes Schindelin --- Documentation/config/core.txt | 9 +++++++++ config.c | 8 +++++++- 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt index b6740b750f03aa..ab750979dd9e01 100644 --- a/Documentation/config/core.txt +++ b/Documentation/config/core.txt @@ -755,3 +755,12 @@ core.WSLCompat:: The default value is false. When set to true, Git will set the mode bits of the file in the way of wsl, so that the executable flag of files can be set or read correctly. + +core.configWriteLockTimeoutMS:: + When processes try to write to the config concurrently, it is likely + that one process "wins" and the other process(es) fail to lock the + config file. By configuring a timeout larger than zero, Git can be + told to try to lock the config again a couple times within the + specified timeout. If the timeout is configure to zero (which is the + default), Git will fail immediately when the config is already + locked. diff --git a/config.c b/config.c index d5b2a9b5099687..c8eb139c9fb2d1 100644 --- a/config.c +++ b/config.c @@ -3324,6 +3324,7 @@ int git_config_set_multivar_in_file_gently(const char *config_filename, const char *value_pattern, unsigned flags) { + static unsigned long timeout_ms = ULONG_MAX; int fd = -1, in_fd = -1; int ret; struct lock_file lock = LOCK_INIT; @@ -3342,11 +3343,16 @@ int git_config_set_multivar_in_file_gently(const char *config_filename, if (!config_filename) config_filename = filename_buf = git_pathdup("config"); + if ((long)timeout_ms < 0 && + git_config_get_ulong("core.configWriteLockTimeoutMS", &timeout_ms)) + timeout_ms = 0; + /* * The lock serves a purpose in addition to locking: the new * contents of .git/config will be written into it. */ - fd = hold_lock_file_for_update(&lock, config_filename, 0); + fd = hold_lock_file_for_update_timeout(&lock, config_filename, 0, + timeout_ms); if (fd < 0) { error_errno(_("could not lock config file %s"), config_filename); ret = CONFIG_NO_LOCK;