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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
Download patch file Download diff file Expand all files Collapse all files

75
src/wayland-server.c
View file

@ -205,8 +205,6 @@ deref_new_objects(struct wl_closure *closure)
}
}
static int
wl_client_connection_data(int fd, uint32_t mask, void *data)
{
@ -218,20 +216,33 @@ wl_client_connection_data(int fd, uint32_t mask, void *data)
const struct wl_message *message;
uint32_t p[2];
int opcode, size;
uint32_t cmask = 0;
int len;
if (mask & WL_EVENT_READABLE)
cmask |= WL_CONNECTION_READABLE;
if (mask & WL_EVENT_WRITABLE)
cmask |= WL_CONNECTION_WRITABLE;
len = wl_connection_data(connection, cmask);
if (len < 0) {
if (mask & (WL_EVENT_ERROR | WL_EVENT_HANGUP)) {
wl_client_destroy(client);
return 1;
}
if (mask & WL_EVENT_WRITABLE) {
len = wl_connection_flush(connection);
if (len < 0 && errno != EAGAIN) {
wl_client_destroy(client);
return 1;
} else if (len >= 0) {
wl_event_source_fd_update(client->source,
WL_EVENT_READABLE);
}
}
len = 0;
if (mask & WL_EVENT_READABLE) {
len = wl_connection_read(connection);
if (len < 0 && errno != EAGAIN) {
wl_client_destroy(client);
return 1;
}
}
while ((size_t) len >= sizeof p) {
wl_connection_copy(connection, p, sizeof p);
opcode = p[1] & 0xffff;
@ -296,27 +307,10 @@ wl_client_connection_data(int fd, uint32_t mask, void *data)
return 1;
}
static int
wl_client_connection_update(struct wl_connection *connection,
uint32_t mask, void *data)
{
struct wl_client *client = data;
uint32_t emask = 0;
client->mask = mask;
if (mask & WL_CONNECTION_READABLE)
emask |= WL_EVENT_READABLE;
if (mask & WL_CONNECTION_WRITABLE)
emask |= WL_EVENT_WRITABLE;
return wl_event_source_fd_update(client->source, emask);
}
WL_EXPORT void
wl_client_flush(struct wl_client *client)
{
if (client->mask & WL_CONNECTION_WRITABLE)
wl_connection_data(client->connection, WL_CONNECTION_WRITABLE);
wl_connection_flush(client->connection);
}
WL_EXPORT struct wl_display *
@ -352,8 +346,7 @@ wl_client_create(struct wl_display *display, int fd)
return NULL;
}
client->connection =
wl_connection_create(fd, wl_client_connection_update, client);
client->connection = wl_connection_create(fd);
if (client->connection == NULL) {
free(client);
return NULL;
@ -1103,8 +1096,28 @@ wl_display_run(struct wl_display *display)
{
display->run = 1;
while (display->run)
while (display->run) {
wl_display_flush_clients(display);
wl_event_loop_dispatch(display->loop, -1);
}
}
WL_EXPORT void
wl_display_flush_clients(struct wl_display *display)
{
struct wl_client *client, *next;
int ret;
wl_list_for_each_safe(client, next, &display->client_list, link) {
ret = wl_connection_flush(client->connection);
if (ret < 0 && errno == EAGAIN) {
wl_event_source_fd_update(client->source,
WL_EVENT_WRITABLE |
WL_EVENT_READABLE);
} else if (ret < 0) {
wl_client_destroy(client);
}
}
}
static int