From 3fbc77ef1aee3660af8a5563e5347b839085f03c 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 d52fc67af13efc..2ae54f3df3b4d4 100644 --- a/Documentation/config/core.txt +++ b/Documentation/config/core.txt @@ -749,3 +749,12 @@ core.abbrev:: If set to "no", no abbreviation is made and the object names are shown in their full length. The minimum length is 4. + +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 7176f800e1607b..513f1dcb15d322 100644 --- a/config.c +++ b/config.c @@ -3202,6 +3202,7 @@ 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; @@ -3222,11 +3223,16 @@ 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;