@samitouri / QOSamiQemu / commits / 3ca9eff4af

ui/vnc: make the worker thread per-VncDisplay

The VNC encoding worker thread was using a single global queue shared across all VNC displays, with no way to stop it. This made it impossible to properly clean up resources when a VncDisplay is freed. Move the VncJobQueue from a file-scoped global to a per-VncDisplay member, so each display owns its worker thread and queue. Add vnc_stop_worker_thread() to perform an orderly shutdown: signal the thread to exit, join it, and destroy the queue. The thread is now created as QEMU_THREAD_JOINABLE instead of QEMU_THREAD_DETACHED. Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

Marc-André Lureau committed Apr 7, 2026 at 16:03 UTC 3ca9eff4aff07489d885691f6fa5db199c2674a9

4 files changed +46 -24

ui/vnc-jobs.c

+40 -22

@@ -29,8 +29,6 @@

29 #include "qemu/osdep.h"

30 #include "vnc.h"

31 #include "vnc-jobs.h"

32 -#include "qemu/sockets.h"

33 -#include "qemu/main-loop.h"

32 #include "trace.h"

34 /*

@@ -56,17 +54,10 @@ struct VncJobQueue {

54 QemuCond cond;

55 QemuMutex mutex;

56 QemuThread thread;

57 + bool exit;

58 QTAILQ_HEAD(, VncJob) jobs;

59 };

62 -typedef struct VncJobQueue VncJobQueue;

63 -

64 -/*

65 - * We use a single global queue, but most of the functions are

66 - * already reentrant, so we can easily add more than one encoding thread

67 - */

68 -static VncJobQueue *queue;

69 -

61 static void vnc_lock_queue(VncJobQueue *queue)

62 {

63 qemu_mutex_lock(&queue->mutex);

@@ -125,12 +116,15 @@ static void vnc_job_free(VncJob *job)

116 */

117 void vnc_job_push(VncJob *job)

118 {

119 + VncJobQueue *queue = job->vs->vd->queue;

120 +

121 assert(!QTAILQ_IN_USE(job, next));

122

123 if (QLIST_EMPTY(&job->rectangles)) {

124 vnc_job_free(job);

125 } else {

126 vnc_lock_queue(queue);

127 + assert(!queue->exit);

128 QTAILQ_INSERT_TAIL(&queue->jobs, job, next);

129 qemu_cond_broadcast(&queue->cond);

130 vnc_unlock_queue(queue);

@@ -139,6 +133,7 @@ void vnc_job_push(VncJob *job)

133

134 static bool vnc_has_job_locked(VncState *vs)

135 {

136 + VncJobQueue *queue = vs->vd->queue;

137 VncJob *job;

138

139 QTAILQ_FOREACH(job, &queue->jobs, next) {

@@ -151,6 +146,8 @@ static bool vnc_has_job_locked(VncState *vs)

146

147 void vnc_jobs_join(VncState *vs)

148 {

149 + VncJobQueue *queue = vs->vd->queue;

150 +

151 vnc_lock_queue(queue);

152 while (vnc_has_job_locked(vs)) {

153 qemu_cond_wait(&queue->cond, &queue->mutex);

@@ -252,9 +249,13 @@ static int vnc_worker_thread_loop(VncJobQueue *queue)

249 int saved_offset;

250

251 vnc_lock_queue(queue);

255 - while (QTAILQ_EMPTY(&queue->jobs)) {

252 + while (QTAILQ_EMPTY(&queue->jobs) && !queue->exit) {

253 qemu_cond_wait(&queue->cond, &queue->mutex);

254 }

255 + if (queue->exit) {

256 + vnc_unlock_queue(queue);

257 + return 1;

258 + }

259 job = QTAILQ_FIRST(&queue->jobs);

260 vnc_unlock_queue(queue);

261

@@ -340,7 +341,7 @@ disconnected:

341 return 0;

342 }

343

343 -static VncJobQueue *vnc_queue_init(void)

344 +static VncJobQueue *vnc_queue_new(void)

345 {

346 VncJobQueue *queue = g_new0(VncJobQueue, 1);

347

@@ -350,29 +351,46 @@ static VncJobQueue *vnc_queue_init(void)

351 return queue;

352 }

353

354 +static void vnc_queue_free(VncJobQueue *queue)

355 +{

356 + qemu_cond_destroy(&queue->cond);

357 + qemu_mutex_destroy(&queue->mutex);

358 + g_free(queue);

359 +}

360 +

361 static void *vnc_worker_thread(void *arg)

362 {

363 VncJobQueue *queue = arg;

364

365 while (!vnc_worker_thread_loop(queue)) ;

358 - g_assert_not_reached();

366 +

367 return NULL;

368 }

369

362 -static bool vnc_worker_thread_running(void)

370 +void vnc_start_worker_thread(VncDisplay *vd)

371 {

364 - return queue; /* Check global queue */

372 + assert(vd->queue == NULL);

373 +

374 + vd->queue = vnc_queue_new();

375 + qemu_thread_create(&vd->queue->thread, "vnc_worker", vnc_worker_thread, vd->queue,

376 + QEMU_THREAD_JOINABLE);

377 }

378

367 -void vnc_start_worker_thread(void)

379 +void vnc_stop_worker_thread(VncDisplay *vd)

380 {

369 - VncJobQueue *q;

381 + VncJobQueue *queue = vd->queue;

382

371 - if (vnc_worker_thread_running())

383 + if (!queue) {

384 return;

385 + }

386 +

387 + /* all VNC clients must have finished before we can stop the worker thread */

388 + vnc_lock_queue(queue);

389 + assert(QTAILQ_EMPTY(&queue->jobs));

390 + queue->exit = true;

391 + qemu_cond_broadcast(&queue->cond);

392 + vnc_unlock_queue(queue);

393

374 - q = vnc_queue_init();

375 - qemu_thread_create(&q->thread, "vnc_worker", vnc_worker_thread, q,

376 - QEMU_THREAD_DETACHED);

377 - queue = q; /* Set global queue */

394 + qemu_thread_join(&queue->thread);

395 + g_clear_pointer(&vd->queue, vnc_queue_free);

396 }

ui/vnc-jobs.h

+2 -1

@@ -37,7 +37,8 @@ void vnc_job_push(VncJob *job);

37 void vnc_jobs_join(VncState *vs);

39 void vnc_jobs_consume_buffer(VncState *vs);

40 -void vnc_start_worker_thread(void);

40 +void vnc_start_worker_thread(VncDisplay *vd);

41 +void vnc_stop_worker_thread(VncDisplay *vd);

43 /* Locks */

44 static inline int vnc_trylock_display(VncDisplay *vd)

ui/vnc.c

+2 -1

@@ -3457,7 +3457,7 @@ void vnc_display_init(const char *id, Error **errp)

3457 vd->share_policy = VNC_SHARE_POLICY_ALLOW_EXCLUSIVE;

3458 vd->connections_limit = 32;

3459

3460 - vnc_start_worker_thread();

3460 + vnc_start_worker_thread(vd);

3461

3462 register_displaychangelistener(&vd->dcl);

3463 vd->kbd = qkbd_state_init(vd->dcl.con);

@@ -3513,6 +3513,7 @@ static void vnc_display_free(VncDisplay *vd)

3513

3514 assert(QTAILQ_EMPTY(&vd->clients));

3515

3516 + vnc_stop_worker_thread(vd);

3517 vnc_display_close(vd);

3518 unregister_displaychangelistener(&vd->dcl);

3519 qkbd_state_free(vd->kbd);

ui/vnc.h

@@ -62,6 +62,7 @@

63 typedef struct VncState VncState;

64 typedef struct VncJob VncJob;

65 +typedef struct VncJobQueue VncJobQueue;

66 typedef struct VncRect VncRect;

67 typedef struct VncRectEntry VncRectEntry;

@@ -158,6 +159,7 @@ struct VncDisplay

159 int ledstate;

160 QKbdState *kbd;

161 QemuMutex mutex;

162 + VncJobQueue *queue;

163

164 int cursor_msize;

165 uint8_t *cursor_mask;