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main-loop: switch to g_poll() on POSIX hosts

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Use g_poll(3) instead of select(2).  Well, this is kind of a cheat.
It's true that we're now using g_poll(3) on POSIX hosts but the *_fill()
and *_poll() functions are still using rfds/wfds/xfds.

We've set the scene to start converting *_fill() and *_poll() functions
step-by-step until no more rfds/wfds/xfds users remain.  Then we'll drop
the temporary gpollfds_from_select() and gpollfds_to_select() functions
and be left with native g_poll(2).

On Windows things are a little crazy: convert from rfds/wfds/xfds to
GPollFDs, back to rfds/wfds/xfds, call select(2), rfds/wfds/xfds back to
GPollFDs, and finally back to rfds/wfds/xfds again.  This is only
temporary and keeps the Windows build working through the following
patches.  We'll drop this excessive conversion later and be left with a
single GPollFDs -> select(2) -> GPollFDs sequence that allows Windows to
use select(2) while the rest of QEMU only knows about GPollFD.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1361356113-11049-3-git-send-email-stefanha@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Stefan Hajnoczi 2013-02-20 11:28:25 +01:00 committed by Anthony Liguori
parent 134a03e0b3
commit cbff4b342b
1 changed files with 129 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

137
main-loop.c
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@ -117,6 +117,8 @@ void qemu_notify_event(void)
aio_notify(qemu_aio_context);
}
static GArray *gpollfds;
int qemu_init_main_loop(void)
{
int ret;
@ -133,6 +135,7 @@ int qemu_init_main_loop(void)
return ret;
}
gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
qemu_aio_context = aio_context_new();
src = aio_get_g_source(qemu_aio_context);
g_source_attach(src, NULL);
@ -146,6 +149,62 @@ static GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
static int n_poll_fds;
static int max_priority;
/* Load rfds/wfds/xfds into gpollfds. Will be removed a few commits later. */
static void gpollfds_from_select(void)
{
int fd;
for (fd = 0; fd <= nfds; fd++) {
int events = 0;
if (FD_ISSET(fd, &rfds)) {
events |= G_IO_IN | G_IO_HUP | G_IO_ERR;
}
if (FD_ISSET(fd, &wfds)) {
events |= G_IO_OUT | G_IO_ERR;
}
if (FD_ISSET(fd, &xfds)) {
events |= G_IO_PRI;
}
if (events) {
GPollFD pfd = {
.fd = fd,
.events = events,
};
g_array_append_val(gpollfds, pfd);
}
}
}
/* Store gpollfds revents into rfds/wfds/xfds. Will be removed a few commits
* later.
*/
static void gpollfds_to_select(int ret)
{
int i;
FD_ZERO(&rfds);
FD_ZERO(&wfds);
FD_ZERO(&xfds);
if (ret <= 0) {
return;
}
for (i = 0; i < gpollfds->len; i++) {
int fd = g_array_index(gpollfds, GPollFD, i).fd;
int revents = g_array_index(gpollfds, GPollFD, i).revents;
if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) {
FD_SET(fd, &rfds);
}
if (revents & (G_IO_OUT | G_IO_ERR)) {
FD_SET(fd, &wfds);
}
if (revents & G_IO_PRI) {
FD_SET(fd, &xfds);
}
}
}
#ifndef _WIN32
static void glib_select_fill(int *max_fd, fd_set *rfds, fd_set *wfds,
fd_set *xfds, uint32_t *cur_timeout)
@ -212,22 +271,22 @@ static void glib_select_poll(fd_set *rfds, fd_set *wfds, fd_set *xfds,
static int os_host_main_loop_wait(uint32_t timeout)
{
struct timeval tv, *tvarg = NULL;
int ret;
glib_select_fill(&nfds, &rfds, &wfds, &xfds, &timeout);
if (timeout < UINT32_MAX) {
tvarg = &tv;
tv.tv_sec = timeout / 1000;
tv.tv_usec = (timeout % 1000) * 1000;
}
if (timeout > 0) {
qemu_mutex_unlock_iothread();
}
ret = select(nfds + 1, &rfds, &wfds, &xfds, tvarg);
/* We'll eventually drop fd_set completely. But for now we still have
* *_fill() and *_poll() functions that use rfds/wfds/xfds.
*/
gpollfds_from_select();
ret = g_poll((GPollFD *)gpollfds->data, gpollfds->len, timeout);
gpollfds_to_select(ret);
if (timeout > 0) {
qemu_mutex_lock_iothread();
@ -327,6 +386,55 @@ void qemu_fd_register(int fd)
FD_CONNECT | FD_WRITE | FD_OOB);
}
static int pollfds_fill(GArray *pollfds, fd_set *rfds, fd_set *wfds,
fd_set *xfds)
{
int nfds = -1;
int i;
for (i = 0; i < pollfds->len; i++) {
GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
int fd = pfd->fd;
int events = pfd->events;
if (events & (G_IO_IN | G_IO_HUP | G_IO_ERR)) {
FD_SET(fd, rfds);
nfds = MAX(nfds, fd);
}
if (events & (G_IO_OUT | G_IO_ERR)) {
FD_SET(fd, wfds);
nfds = MAX(nfds, fd);
}
if (events & G_IO_PRI) {
FD_SET(fd, xfds);
nfds = MAX(nfds, fd);
}
}
return nfds;
}
static void pollfds_poll(GArray *pollfds, int nfds, fd_set *rfds,
fd_set *wfds, fd_set *xfds)
{
int i;
for (i = 0; i < pollfds->len; i++) {
GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
int fd = pfd->fd;
int revents = 0;
if (FD_ISSET(fd, rfds)) {
revents |= G_IO_IN | G_IO_HUP | G_IO_ERR;
}
if (FD_ISSET(fd, wfds)) {
revents |= G_IO_OUT | G_IO_ERR;
}
if (FD_ISSET(fd, xfds)) {
revents |= G_IO_PRI;
}
pfd->revents = revents & pfd->events;
}
}
static int os_host_main_loop_wait(uint32_t timeout)
{
GMainContext *context = g_main_context_default();
@ -382,12 +490,24 @@ static int os_host_main_loop_wait(uint32_t timeout)
* improve socket latency.
*/
/* This back-and-forth between GPollFDs and select(2) is temporary. We'll
* drop it in a couple of patches, I promise :).
*/
gpollfds_from_select();
FD_ZERO(&rfds);
FD_ZERO(&wfds);
FD_ZERO(&xfds);
nfds = pollfds_fill(gpollfds, &rfds, &wfds, &xfds);
if (nfds >= 0) {
select_ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
if (select_ret != 0) {
timeout = 0;
}
if (select_ret > 0) {
pollfds_poll(gpollfds, nfds, &rfds, &wfds, &xfds);
}
}
gpollfds_to_select(select_ret);
return select_ret || g_poll_ret;
}
@ -403,6 +523,7 @@ int main_loop_wait(int nonblocking)
}
/* poll any events */
g_array_set_size(gpollfds, 0); /* reset for new iteration */
/* XXX: separate device handlers from system ones */
nfds = -1;
FD_ZERO(&rfds);