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Change filedescriptor API to be thread safe

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The update callback for the file descriptors was always a bit awkward and
un-intuitive.  The idea was that whenever the protocol code needed to
write data to the fd it would call the 'update' function.  This function
would adjust the mainloop so that it polls for POLLOUT on the fd so we
can eventually flush the data to the socket.

The problem is that in multi-threaded applications, any thread can issue
a request, which writes data to the output buffer and thus triggers the
update callback.  Thus, we'll be calling out with the display mutex
held and may call from any thread.

The solution is to eliminate the udpate callback and just require that
the application or server flushes all connection buffers before blocking.
This turns out to be a simpler API, although we now require clients to
deal with EAGAIN and non-blocking writes.  It also saves a few syscalls,
since the socket will be writable most of the time and most writes will
complete, so we avoid changing epoll to poll for POLLOUT, then write and
then change it back for each write.
This commit is contained in:
Kristian Høgsberg 2012-10-04 16:54:22 -04:00
parent 0371668dcc
commit 53d24713a3
9 changed files with 150 additions and 251 deletions
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5
src/wayland-server.h
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@ -34,7 +34,9 @@ extern "C" {
enum {
WL_EVENT_READABLE = 0x01,
WL_EVENT_WRITABLE = 0x02
WL_EVENT_WRITABLE = 0x02,
WL_EVENT_HANGUP = 0x04,
WL_EVENT_ERROR = 0x08
};
struct wl_event_loop;
@ -88,6 +90,7 @@ struct wl_event_loop *wl_display_get_event_loop(struct wl_display *display);
int wl_display_add_socket(struct wl_display *display, const char *name);
void wl_display_terminate(struct wl_display *display);
void wl_display_run(struct wl_display *display);
void wl_display_flush_clients(struct wl_display *display);
typedef void (*wl_global_bind_func_t)(struct wl_client *client, void *data,
uint32_t version, uint32_t id);