From: Michal Sojka Date: Tue, 12 Sep 2017 11:12:31 +0000 (+0200) Subject: uloop: Fix race condition in SIGCHLD handling X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=7a1057604ed2ad83434ed3be03728065b14a5e9c;p=project%2Flibubox.git uloop: Fix race condition in SIGCHLD handling When uloop_process_add() is called outside of uloop_run(), i.e. not from a callback (which is the case of at least utrace and ujail), child events can be missed. The reason is that when SIGCHILD handler is installed in uloop_run(), after the uloop_process_add() is called, then an initial signal could be missed. Commit 4e3a47a ("uloop: use a waker for notifying sigchld and loop cancel events", 2016-06-09) solved a similar problem and introduced uloop_init() but forgot to move a call to uloop_setup_signals() there. This is what this commit does. Now, uloop_process_add() can be called any time after uloop_init() without missing any event. Signed-off-by: Michal Sojka Acked-by: Yousong Zhou --- diff --git a/uloop.c b/uloop.c index d2f41bb..3813e18 100644 --- a/uloop.c +++ b/uloop.c @@ -116,6 +116,8 @@ static int waker_init(void) return 0; } +static void uloop_setup_signals(bool add); + int uloop_init(void) { if (uloop_init_pollfd() < 0) @@ -126,6 +128,8 @@ int uloop_init(void) return -1; } + uloop_setup_signals(true); + return 0; } @@ -525,12 +529,7 @@ int uloop_run_timeout(int timeout) int next_time = 0; struct timeval tv; - /* - * Handlers are only updated for the first call to uloop_run() (and restored - * when this call is done). - */ - if (!uloop_run_depth++) - uloop_setup_signals(true); + uloop_run_depth++; uloop_status = 0; uloop_cancelled = false; @@ -553,14 +552,15 @@ int uloop_run_timeout(int timeout) uloop_run_events(next_time); } - if (!--uloop_run_depth) - uloop_setup_signals(false); + --uloop_run_depth; return uloop_status; } void uloop_done(void) { + uloop_setup_signals(false); + if (poll_fd >= 0) { close(poll_fd); poll_fd = -1;