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uloop: use a waker for notifying sigchld and loop cancel events

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Fix a race condition when do_sigchld, uloop_cancelled were set just
before epoll_wait(timeout=-1), resulting the loop stuck in the syscall
without noticing the events just happened

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
This commit is contained in:
Yousong Zhou 2016-06-09 10:20:32 +08:00 committed by Felix Fietkau
parent 1257a38a6e
commit 4e3a47a4cb
3 changed files with 74 additions and 6 deletions
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2
uloop-epoll.c
View file

@ -23,7 +23,7 @@
#define EPOLLRDHUP 0x2000
#endif
int uloop_init(void)
static int uloop_init_pollfd(void)
{
if (poll_fd >= 0)
return 0;

2
uloop-kqueue.c
View file

@ -15,7 +15,7 @@
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
int uloop_init(void)
static int uloop_init_pollfd(void)
{
struct timespec timeout = { 0, 0 };
struct kevent ev = {};

74
uloop.c
View file

@ -63,6 +63,8 @@ static bool do_sigchld = false;
static struct uloop_fd_event cur_fds[ULOOP_MAX_EVENTS];
static int cur_fd, cur_nfds;
int uloop_fd_add(struct uloop_fd *sock, unsigned int flags);
#ifdef USE_KQUEUE
#include "uloop-kqueue.c"
#endif
@ -71,6 +73,59 @@ static int cur_fd, cur_nfds;
#include "uloop-epoll.c"
#endif
static void waker_consume(struct uloop_fd *fd, unsigned int events)
{
char buf[4];
while (read(fd->fd, buf, 4) > 0)
;
}
static int waker_pipe = -1;
static struct uloop_fd waker_fd = {
.fd = -1,
.cb = waker_consume,
};
static void waker_init_fd(int fd)
{
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
}
static int waker_init(void)
{
int fds[2];
if (waker_pipe >= 0)
return 0;
if (pipe(fds) < 0)
return -1;
waker_init_fd(fds[0]);
waker_init_fd(fds[1]);
waker_fd.fd = fds[0];
waker_fd.cb = waker_consume;
uloop_fd_add(&waker_fd, ULOOP_READ);
return 0;
}
int uloop_init(void)
{
if (uloop_init_pollfd() < 0)
return -1;
if (waker_init() < 0) {
uloop_done();
return -1;
}
return 0;
}
static bool uloop_fd_stack_event(struct uloop_fd *fd, int events)
{
struct uloop_fd_stack *cur;
@ -328,14 +383,21 @@ static void uloop_handle_processes(void)
}
static void uloop_signal_wake(void)
{
write(waker_pipe, "w", 1);
}
static void uloop_handle_sigint(int signo)
{
uloop_cancelled = true;
uloop_signal_wake();
}
static void uloop_sigchld(int signo)
{
do_sigchld = true;
uloop_signal_wake();
}
static void uloop_install_handler(int signum, void (*handler)(int), struct sigaction* old, bool add)
@ -477,11 +539,17 @@ void uloop_run(void)
void uloop_done(void)
{
if (poll_fd < 0)
return;
if (poll_fd >= 0) {
close(poll_fd);
poll_fd = -1;
}
if (waker_pipe >= 0) {
uloop_fd_delete(&waker_fd);
close(waker_pipe);
close(waker_fd.fd);
waker_pipe = -1;
}
uloop_clear_timeouts();
uloop_clear_processes();