vo: use mp_poll wrapper in wait_events when applicable

On linux, several platforms poll for events over a fd. This has ms
accuracy, but mpv's timer is in ns now so lots of precision is lost. We
can use an mp_poll wrapper to use ppoll instead which takes a timespec
directly with nanosecond precision. On systems without ppoll this falls
back to old poll behavior. On wayland, we don't actually use this
because ppoll completely messes up the event loop for some unknown
reason.

5 files changed, 27 insertions, 6 deletions

diff --git a/meson.build b/meson.build
index 91b8e84b15..4485c74a56 100644
--- a/meson.build
+++ b/meson.build
@@ -424,6 +424,9 @@ if posix and not darwin
                      'osdep/timer-linux.c')
 endif
 
+features += {'ppoll': cc.has_function('ppoll', args: '-D_GNU_SOURCE',
+                                      prefix: '#include <poll.h>')}
+
 cd_devices = {
     'windows': 'D:',
     'cygwin': 'D:',
diff --git a/osdep/poll_wrapper.c b/osdep/poll_wrapper.c
index e4ad0f698a..48a66d2cd1 100644
--- a/osdep/poll_wrapper.c
+++ b/osdep/poll_wrapper.c
@@ -20,9 +20,20 @@
 #include <sys/select.h>
 #include <stdio.h>
 
+#include "config.h"
 #include "poll_wrapper.h"
+#include "timer.h"
 
 
+int mp_poll(struct pollfd *fds, int nfds, int64_t timeout_ns)
+{
+#if HAVE_PPOLL
+    struct timespec ts = mp_time_ns_to_realtime(timeout_ns);
+    return ppoll(fds, nfds, &ts, NULL);
+#endif
+    return poll(fds, nfds, timeout_ns / 1e6);
+}
+
 // poll shim that supports device files on macOS.
 int polldev(struct pollfd fds[], nfds_t nfds, int timeout)
 {
diff --git a/osdep/poll_wrapper.h b/osdep/poll_wrapper.h
index 8593c1e77c..b359ed39a0 100644
--- a/osdep/poll_wrapper.h
+++ b/osdep/poll_wrapper.h
@@ -1,7 +1,12 @@
 #pragma once
 
 #include <poll.h>
+#include <stdint.h>
 
 // Behaves like poll(3) but works for device files on macOS.
 // Only supports POLLIN and POLLOUT.
 int polldev(struct pollfd fds[], nfds_t nfds, int timeout);
+
+// Generic polling wrapper. It will try and use higher resolution
+// polling (ppoll) if available.
+int mp_poll(struct pollfd *fds, int nfds, int64_t timeout_ns);
diff --git a/video/out/drm_common.c b/video/out/drm_common.c
index dd53793dbb..f8d68dfa81 100644
--- a/video/out/drm_common.c
+++ b/video/out/drm_common.c
@@ -42,6 +42,7 @@
 #include "common/msg.h"
 #include "options/m_config.h"
 #include "osdep/io.h"
+#include "osdep/poll_wrapper.h"
 #include "osdep/timer.h"
 #include "misc/ctype.h"
 #include "video/out/vo.h"
@@ -283,12 +284,12 @@ static void vt_switcher_destroy(struct vt_switcher *s)
     close(vt_switcher_pipe[1]);
 }
 
-static void vt_switcher_poll(struct vt_switcher *s, int timeout_ms)
+static void vt_switcher_poll(struct vt_switcher *s, int timeout_ns)
 {
     struct pollfd fds[1] = {
         { .events = POLLIN, .fd = vt_switcher_pipe[0] },
     };
-    poll(fds, 1, timeout_ms);
+    mp_poll(fds, 1, timeout_ns);
     if (!fds[0].revents)
         return;
 
@@ -1309,8 +1310,8 @@ void vo_drm_wait_events(struct vo *vo, int64_t until_time_ns)
     struct vo_drm_state *drm = vo->drm;
     if (drm->vt_switcher_active) {
         int64_t wait_ns = until_time_ns - mp_time_ns();
-        int timeout_ms = MPCLAMP(wait_ns / 1e6, 1, 10000);
-        vt_switcher_poll(&drm->vt_switcher, timeout_ms);
+        int64_t timeout_ns = MPCLAMP(wait_ns, 1e6, 1e10);
+        vt_switcher_poll(&drm->vt_switcher, timeout_ns);
     } else {
         vo_wait_default(vo, until_time_ns);
     }
diff --git a/video/out/x11_common.c b/video/out/x11_common.c
index be5002b068..f77f4c86f8 100644
--- a/video/out/x11_common.c
+++ b/video/out/x11_common.c
@@ -55,6 +55,7 @@
 #include "vo.h"
 #include "win_state.h"
 #include "osdep/io.h"
+#include "osdep/poll_wrapper.h"
 #include "osdep/timer.h"
 #include "osdep/subprocess.h"
 
@@ -2177,9 +2178,9 @@ void vo_x11_wait_events(struct vo *vo, int64_t until_time_ns)
         { .fd = x11->wakeup_pipe[0], .events = POLLIN },
     };
     int64_t wait_ns = until_time_ns - mp_time_ns();
-    int timeout_ms = MPCLAMP(wait_ns / 1e6, 1, 10000);
+    int64_t timeout_ns = MPCLAMP(wait_ns, 1e6, 1e10);
 
-    poll(fds, 2, timeout_ms);
+    mp_poll(fds, 2, timeout_ns);
 
     if (fds[1].revents & POLLIN)
         mp_flush_wakeup_pipe(x11->wakeup_pipe[0]);