qemu/ui/vnc-jobs-async.c
Corentin Chary 175b2a6e4b vnc: don't mess up with iohandlers in the vnc thread
The threaded VNC servers messed up with QEMU fd handlers without
any kind of locking, and that can cause some nasty race conditions.

Using qemu_mutex_lock_iothread() won't work because vnc_dpy_cpy(),
which will wait for the current job queue to finish, can be called with
the iothread lock held.

Instead, we now store the data in a temporary buffer, and use a bottom
half to notify the main thread that new data is available.

vnc_[un]lock_ouput() is still needed to access VncState members like
abort, csock or jobs_buffer.

Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2012-03-14 16:22:46 -05:00

352 lines
9.1 KiB
C

/*
* QEMU VNC display driver
*
* Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
* Copyright (C) 2006 Fabrice Bellard
* Copyright (C) 2009 Red Hat, Inc
* Copyright (C) 2010 Corentin Chary <corentin.chary@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "vnc.h"
#include "vnc-jobs.h"
#include "qemu_socket.h"
/*
* Locking:
*
* There is three levels of locking:
* - jobs queue lock: for each operation on the queue (push, pop, isEmpty?)
* - VncDisplay global lock: mainly used for framebuffer updates to avoid
* screen corruption if the framebuffer is updated
* while the worker is doing something.
* - VncState::output lock: used to make sure the output buffer is not corrupted
* if two threads try to write on it at the same time
*
* While the VNC worker thread is working, the VncDisplay global lock is hold
* to avoid screen corruptions (this does not block vnc_refresh() because it
* uses trylock()) but the output lock is not hold because the thread work on
* its own output buffer.
* When the encoding job is done, the worker thread will hold the output lock
* and copy its output buffer in vs->output.
*/
struct VncJobQueue {
QemuCond cond;
QemuMutex mutex;
QemuThread thread;
Buffer buffer;
bool exit;
QTAILQ_HEAD(, VncJob) jobs;
};
typedef struct VncJobQueue VncJobQueue;
/*
* We use a single global queue, but most of the functions are
* already reetrant, so we can easilly add more than one encoding thread
*/
static VncJobQueue *queue;
static void vnc_lock_queue(VncJobQueue *queue)
{
qemu_mutex_lock(&queue->mutex);
}
static void vnc_unlock_queue(VncJobQueue *queue)
{
qemu_mutex_unlock(&queue->mutex);
}
VncJob *vnc_job_new(VncState *vs)
{
VncJob *job = g_malloc0(sizeof(VncJob));
job->vs = vs;
vnc_lock_queue(queue);
QLIST_INIT(&job->rectangles);
vnc_unlock_queue(queue);
return job;
}
int vnc_job_add_rect(VncJob *job, int x, int y, int w, int h)
{
VncRectEntry *entry = g_malloc0(sizeof(VncRectEntry));
entry->rect.x = x;
entry->rect.y = y;
entry->rect.w = w;
entry->rect.h = h;
vnc_lock_queue(queue);
QLIST_INSERT_HEAD(&job->rectangles, entry, next);
vnc_unlock_queue(queue);
return 1;
}
void vnc_job_push(VncJob *job)
{
vnc_lock_queue(queue);
if (queue->exit || QLIST_EMPTY(&job->rectangles)) {
g_free(job);
} else {
QTAILQ_INSERT_TAIL(&queue->jobs, job, next);
qemu_cond_broadcast(&queue->cond);
}
vnc_unlock_queue(queue);
}
static bool vnc_has_job_locked(VncState *vs)
{
VncJob *job;
QTAILQ_FOREACH(job, &queue->jobs, next) {
if (job->vs == vs || !vs) {
return true;
}
}
return false;
}
bool vnc_has_job(VncState *vs)
{
bool ret;
vnc_lock_queue(queue);
ret = vnc_has_job_locked(vs);
vnc_unlock_queue(queue);
return ret;
}
void vnc_jobs_clear(VncState *vs)
{
VncJob *job, *tmp;
vnc_lock_queue(queue);
QTAILQ_FOREACH_SAFE(job, &queue->jobs, next, tmp) {
if (job->vs == vs || !vs) {
QTAILQ_REMOVE(&queue->jobs, job, next);
}
}
vnc_unlock_queue(queue);
}
void vnc_jobs_join(VncState *vs)
{
vnc_lock_queue(queue);
while (vnc_has_job_locked(vs)) {
qemu_cond_wait(&queue->cond, &queue->mutex);
}
vnc_unlock_queue(queue);
vnc_jobs_consume_buffer(vs);
}
void vnc_jobs_consume_buffer(VncState *vs)
{
bool flush;
vnc_lock_output(vs);
if (vs->jobs_buffer.offset) {
vnc_write(vs, vs->jobs_buffer.buffer, vs->jobs_buffer.offset);
buffer_reset(&vs->jobs_buffer);
}
flush = vs->csock != -1 && vs->abort != true;
vnc_unlock_output(vs);
if (flush) {
vnc_flush(vs);
}
}
/*
* Copy data for local use
*/
static void vnc_async_encoding_start(VncState *orig, VncState *local)
{
local->vnc_encoding = orig->vnc_encoding;
local->features = orig->features;
local->ds = orig->ds;
local->vd = orig->vd;
local->lossy_rect = orig->lossy_rect;
local->write_pixels = orig->write_pixels;
local->clientds = orig->clientds;
local->tight = orig->tight;
local->zlib = orig->zlib;
local->hextile = orig->hextile;
local->zrle = orig->zrle;
local->output = queue->buffer;
local->csock = -1; /* Don't do any network work on this thread */
buffer_reset(&local->output);
}
static void vnc_async_encoding_end(VncState *orig, VncState *local)
{
orig->tight = local->tight;
orig->zlib = local->zlib;
orig->hextile = local->hextile;
orig->zrle = local->zrle;
orig->lossy_rect = local->lossy_rect;
queue->buffer = local->output;
}
static int vnc_worker_thread_loop(VncJobQueue *queue)
{
VncJob *job;
VncRectEntry *entry, *tmp;
VncState vs;
int n_rectangles;
int saved_offset;
vnc_lock_queue(queue);
while (QTAILQ_EMPTY(&queue->jobs) && !queue->exit) {
qemu_cond_wait(&queue->cond, &queue->mutex);
}
/* Here job can only be NULL if queue->exit is true */
job = QTAILQ_FIRST(&queue->jobs);
vnc_unlock_queue(queue);
if (queue->exit) {
return -1;
}
vnc_lock_output(job->vs);
if (job->vs->csock == -1 || job->vs->abort == true) {
vnc_unlock_output(job->vs);
goto disconnected;
}
vnc_unlock_output(job->vs);
/* Make a local copy of vs and switch output buffers */
vnc_async_encoding_start(job->vs, &vs);
/* Start sending rectangles */
n_rectangles = 0;
vnc_write_u8(&vs, VNC_MSG_SERVER_FRAMEBUFFER_UPDATE);
vnc_write_u8(&vs, 0);
saved_offset = vs.output.offset;
vnc_write_u16(&vs, 0);
vnc_lock_display(job->vs->vd);
QLIST_FOREACH_SAFE(entry, &job->rectangles, next, tmp) {
int n;
if (job->vs->csock == -1) {
vnc_unlock_display(job->vs->vd);
goto disconnected;
}
n = vnc_send_framebuffer_update(&vs, entry->rect.x, entry->rect.y,
entry->rect.w, entry->rect.h);
if (n >= 0) {
n_rectangles += n;
}
g_free(entry);
}
vnc_unlock_display(job->vs->vd);
/* Put n_rectangles at the beginning of the message */
vs.output.buffer[saved_offset] = (n_rectangles >> 8) & 0xFF;
vs.output.buffer[saved_offset + 1] = n_rectangles & 0xFF;
vnc_lock_output(job->vs);
if (job->vs->csock != -1) {
buffer_reserve(&job->vs->jobs_buffer, vs.output.offset);
buffer_append(&job->vs->jobs_buffer, vs.output.buffer,
vs.output.offset);
/* Copy persistent encoding data */
vnc_async_encoding_end(job->vs, &vs);
qemu_bh_schedule(job->vs->bh);
}
vnc_unlock_output(job->vs);
disconnected:
vnc_lock_queue(queue);
QTAILQ_REMOVE(&queue->jobs, job, next);
vnc_unlock_queue(queue);
qemu_cond_broadcast(&queue->cond);
g_free(job);
return 0;
}
static VncJobQueue *vnc_queue_init(void)
{
VncJobQueue *queue = g_malloc0(sizeof(VncJobQueue));
qemu_cond_init(&queue->cond);
qemu_mutex_init(&queue->mutex);
QTAILQ_INIT(&queue->jobs);
return queue;
}
static void vnc_queue_clear(VncJobQueue *q)
{
qemu_cond_destroy(&queue->cond);
qemu_mutex_destroy(&queue->mutex);
buffer_free(&queue->buffer);
g_free(q);
queue = NULL; /* Unset global queue */
}
static void *vnc_worker_thread(void *arg)
{
VncJobQueue *queue = arg;
qemu_thread_get_self(&queue->thread);
while (!vnc_worker_thread_loop(queue)) ;
vnc_queue_clear(queue);
return NULL;
}
void vnc_start_worker_thread(void)
{
VncJobQueue *q;
if (vnc_worker_thread_running())
return ;
q = vnc_queue_init();
qemu_thread_create(&q->thread, vnc_worker_thread, q, QEMU_THREAD_DETACHED);
queue = q; /* Set global queue */
}
bool vnc_worker_thread_running(void)
{
return queue; /* Check global queue */
}
void vnc_stop_worker_thread(void)
{
if (!vnc_worker_thread_running())
return ;
/* Remove all jobs and wake up the thread */
vnc_lock_queue(queue);
queue->exit = true;
vnc_unlock_queue(queue);
vnc_jobs_clear(NULL);
qemu_cond_broadcast(&queue->cond);
}