[PATCH] config: move flockfile() closer to unlocked functions
- From
Jeff King <peff@peff.net>
- Date
- Mar 30, 2018, 19:26 UTC
- Message-ID
- <20180330192615.GB32338@sigill.intra.peff.net>
On Fri, Mar 30, 2018 at 09:04:13PM +0200, Johannes Schindelin wrote:
> > Probably the flockfile should go into do_config_from_file(), where we > > specify to use the unlocked variants. > > Ah, that makes sense now! I am glad I could also help ;-)
:)
Show 5 quoted lines
> > Yeah, I'll wait to see how your refactor turns out. > > I don't think I'll touch too much in that part of the code. My changes > should not cause merge conflicts with a patch moving the > flockfile()/funlockfile() calls to do_config_from_file().
OK, then let's do this while we're thinking about it:
-- >8 -- Subject: config: move flockfile() closer to unlocked functions
Commit 260d408e32 (config: use getc_unlocked when reading from file, 2015-04-16) taught git_config_from_file() to lock the filehandle so that we could safely use the faster unlocked functions to access the handle.
However, it split the logic into two places:
1. The master lock/unlock happens in git_config_from_file().
2. The decision to use the unlocked functions happens in
do_config_from_file().That means that if anybody calls the latter function, they will accidentally use the unlocked functions without holding the lock. And indeed, git_config_from_stdin() does so.
In practice, this hasn't been a problem since this code isn't generally multi-threaded (and even if some Git program happened to have another thread running, it's unlikely to be reading from stdin). But it's a good practice to make sure we're always holding the lock before using the unlocked functions.
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Jeff King <peff@peff.net> --- I wasn't sure if this was "helped by" or "reported by" or "stumbled-upon-by". :)
config.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/config.c b/config.c index b0c20e6cb8..609ef2f58b 100644 --- a/config.c +++ b/config.c @@ -1426,6 +1426,7 @@ static int do_config_from_file(config_fn_t fn, void *data) { struct config_source top; + int ret; top.u.file = f; top.origin_type = origin_type; @@ -1436,7 +1437,10 @@ static int do_config_from_file(config_fn_t fn, top.do_ungetc = config_file_ungetc; top.do_ftell = config_file_ftell; - return do_config_from(&top, fn, data); + flockfile(f); + ret = do_config_from(&top, fn, data); + funlockfile(f); + return ret; } static int git_config_from_stdin(config_fn_t fn, void *data) @@ -1451,9 +1455,7 @@ int git_config_from_file(config_fn_t fn, const char *filename, void *data) f = fopen_or_warn(filename, "r"); if (f) { - flockfile(f); ret = do_config_from_file(fn, CONFIG_ORIGIN_FILE, filename, filename, f, data); - funlockfile(f); fclose(f); } return ret;
-- 2.17.0.rc2.594.gdb94a0ce02