@@ -410,10 +410,10 @@ static int multifd_send_pages(QEMUFile *f)
for (i = next_channel;; i = (i + 1) % migrate_multifd_channels()) {
p = &multifd_send_state->params[i];
- qemu_mutex_lock(&p->mutex);
+ qemu_sem_wait(&p->ready);
+
if (p->quit) {
error_report("%s: channel %d has already quit!", __func__, i);
- qemu_mutex_unlock(&p->mutex);
return -1;
}
if (!p->pending_job) {
@@ -421,7 +421,6 @@ static int multifd_send_pages(QEMUFile *f)
next_channel = (i + 1) % migrate_multifd_channels();
break;
}
- qemu_mutex_unlock(&p->mutex);
}
assert(!p->pages->num);
assert(!p->pages->block);
@@ -429,7 +428,6 @@ static int multifd_send_pages(QEMUFile *f)
p->packet_num = multifd_send_state->packet_num++;
multifd_send_state->pages = p->pages;
p->pages = pages;
- qemu_mutex_unlock(&p->mutex);
qemu_sem_post(&p->sem);
return 1;
@@ -529,9 +527,9 @@ void multifd_save_cleanup(void)
}
socket_send_channel_destroy(p->c);
p->c = NULL;
- qemu_mutex_destroy(&p->mutex);
qemu_sem_destroy(&p->sem);
qemu_sem_destroy(&p->sem_done);
+ qemu_sem_destroy(&p->ready);
g_free(p->name);
p->name = NULL;
multifd_pages_clear(p->pages);
@@ -586,14 +584,12 @@ static void multifd_send_wait(void)
* Even idle channels will wait for p->sem at the top of the
* loop.
*/
+ qemu_sem_wait(&p->ready);
qemu_sem_post(&p->sem);
trace_multifd_send_wait(migrate_multifd_channels() - i);
qemu_sem_wait(&p->sem_done);
-
- qemu_mutex_lock(&p->mutex);
assert(!p->pending_job || p->quit);
- qemu_mutex_unlock(&p->mutex);
}
/*
@@ -621,20 +617,17 @@ int multifd_send_sync_main(QEMUFile *f)
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
+ qemu_sem_wait(&p->ready);
trace_multifd_send_sync_main_signal(p->id);
- qemu_mutex_lock(&p->mutex);
-
if (p->quit) {
error_report("%s: channel %d has already quit", __func__, i);
- qemu_mutex_unlock(&p->mutex);
return -1;
}
p->packet_num = multifd_send_state->packet_num++;
p->flags |= MULTIFD_FLAG_SYNC;
p->pending_job++;
- qemu_mutex_unlock(&p->mutex);
qemu_sem_post(&p->sem);
}
@@ -685,15 +678,14 @@ static void *multifd_send_thread(void *opaque)
p->num_packets = 1;
while (true) {
+ qemu_sem_post(&p->ready);
qemu_sem_wait(&p->sem);
if (qatomic_read(&multifd_send_state->exiting)) {
- qemu_mutex_lock(&p->mutex);
p->quit = true;
- qemu_mutex_unlock(&p->mutex);
+ qemu_sem_post(&p->sem_done);
break;
}
- qemu_mutex_lock(&p->mutex);
if (p->pending_job) {
uint64_t packet_num = p->packet_num;
@@ -714,7 +706,6 @@ static void *multifd_send_thread(void *opaque)
if (p->normal_num) {
ret = multifd_send_state->ops->send_prepare(p, &local_err);
if (ret != 0) {
- qemu_mutex_unlock(&p->mutex);
break;
}
}
@@ -725,7 +716,6 @@ static void *multifd_send_thread(void *opaque)
p->total_normal_pages += p->normal_num;
p->pages->num = 0;
p->pages->block = NULL;
- qemu_mutex_unlock(&p->mutex);
trace_multifd_send(p->id, packet_num, p->normal_num, flags,
p->next_packet_size);
@@ -753,12 +743,9 @@ static void *multifd_send_thread(void *opaque)
stat64_add(&mig_stats.multifd_bytes, p->next_packet_size);
stat64_add(&mig_stats.transferred, p->next_packet_size);
- qemu_mutex_lock(&p->mutex);
p->pending_job--;
- qemu_mutex_unlock(&p->mutex);
} else {
- qemu_mutex_unlock(&p->mutex);
qemu_sem_post(&p->sem_done);
}
}
@@ -766,11 +753,8 @@ static void *multifd_send_thread(void *opaque)
out:
if (local_err) {
trace_multifd_send_error(p->id);
-
- qemu_mutex_lock(&p->mutex);
p->quit = true;
- qemu_mutex_unlock(&p->mutex);
-
+ qemu_sem_post(&p->ready);
multifd_send_terminate_threads(local_err);
error_free(local_err);
}
@@ -780,12 +764,10 @@ out:
* who pay attention to me.
*/
if (ret != 0) {
- qemu_sem_post(&p->sem_done);
+ p->quit = true;
+ qemu_sem_post(&p->ready);
}
-
- qemu_mutex_lock(&p->mutex);
p->running = false;
- qemu_mutex_unlock(&p->mutex);
rcu_unregister_thread();
migration_threads_remove(thread);
@@ -817,7 +799,7 @@ static void multifd_tls_outgoing_handshake(QIOTask *task,
* is not created, and then tell who pay attention to me.
*/
p->quit = true;
- qemu_sem_post(&p->sem_done);
+ qemu_sem_post(&p->ready);
}
}
@@ -893,14 +875,13 @@ static void multifd_new_send_channel_cleanup(MultiFDSendParams *p,
QIOChannel *ioc, Error *err)
{
migrate_set_error(migrate_get_current(), err);
- /* Error happen, we need to tell who pay attention to me */
- qemu_sem_post(&p->sem_done);
/*
* Although multifd_send_thread is not created, but main migration
* thread need to judge whether it is running, so we need to mark
* its status.
*/
p->quit = true;
+ qemu_sem_post(&p->ready);
object_unref(OBJECT(ioc));
error_free(err);
}
@@ -944,9 +925,9 @@ int multifd_save_setup(Error **errp)
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
- qemu_mutex_init(&p->mutex);
qemu_sem_init(&p->sem, 0);
qemu_sem_init(&p->sem_done, 0);
+ qemu_sem_init(&p->ready, 0);
p->quit = false;
p->pending_job = 0;
p->id = i;
@@ -93,8 +93,8 @@ typedef struct {
/* channel is done transmitting until more pages are queued */
QemuSemaphore sem_done;
- /* this mutex protects the following parameters */
- QemuMutex mutex;
+ QemuSemaphore ready;
+
/* is this channel thread running */
bool running;
/* should this thread finish */
@@ -209,4 +209,3 @@ typedef struct {
void multifd_register_ops(int method, MultiFDMethods *ops);
#endif
-
Bring back the 'ready' semaphore, but this time make it per-channel, so that we can do true lockstep switching of MultiFDPages without taking the channel lock. Drop the channel lock as it now becomes useless. The rules for accessing the MultiFDSendParams are: - between sem and sem_done/ready if we're the channel qemu_sem_post(&p->ready); qemu_sem_wait(&p->sem); <owns p> qemu_sem_post(&p->sem_done); - between ready and sem if we're not the channel qemu_sem_wait(&p->ready); <owns p> qemu_sem_post(&p->sem); Signed-off-by: Fabiano Rosas <farosas@suse.de> --- One issue I can see with this is that we might now have to wait at multifd_send_pages() if a channel takes too long to send it's packet and come back to p->ready. We would need to find a way of ignoring a slow channel and skipping ahead to the next one in line. --- migration/multifd.c | 45 +++++++++++++-------------------------------- migration/multifd.h | 5 ++--- 2 files changed, 15 insertions(+), 35 deletions(-)