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migration/multifd: Drop MultiFDSendParams.quit, cleanup error paths 

Multifd send side has two fields to indicate error quits:

  - MultiFDSendParams.quit
  - &multifd_send_state->exiting

Merge them into the global one.  The replacement is done by changing all
p->quit checks into the global var check.  The global check doesn't need
any lock.

A few more things done on top of this altogether:

  - multifd_send_terminate_threads()

    Moving the xchg() of &multifd_send_state->exiting upper, so as to cover
    the tracepoint, migrate_set_error() and migrate_set_state().

  - multifd_send_sync_main()

    In the 2nd loop, add one more check over the global var to make sure we
    don't keep the looping if QEMU already decided to quit.

  - multifd_tls_outgoing_handshake()

    Use multifd_send_terminate_threads() to set the error state.  That has
    a benefit of updating MigrationState.error to that error too, so we can
    persist that 1st error we hit in that specific channel.

  - multifd_new_send_channel_async()

    Take similar approach like above, drop the migrate_set_error() because
    multifd_send_terminate_threads() already covers that.  Unwrap the helper
    multifd_new_send_channel_cleanup() along the way; not really needed.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240202102857.110210-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Peter Xu 2024-02-02 18:28:37 +08:00
parent 48c0f5d56f
commit 15f3f21d59
2 changed files with 33 additions and 54 deletions
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85
migration/multifd.c
View File

@ -372,6 +372,11 @@ struct {
MultiFDMethods *ops;
} *multifd_send_state;
static bool multifd_send_should_exit(void)
{
return qatomic_read(&multifd_send_state->exiting);
}
/*
* The migration thread can wait on either of the two semaphores. This
* function can be used to kick the main thread out of waiting on either of
@ -409,7 +414,7 @@ static int multifd_send_pages(void)
MultiFDSendParams *p = NULL; /* make happy gcc */
MultiFDPages_t *pages = multifd_send_state->pages;
if (qatomic_read(&multifd_send_state->exiting)) {
if (multifd_send_should_exit()) {
return -1;
}
@ -421,14 +426,11 @@ static int multifd_send_pages(void)
*/
next_channel %= migrate_multifd_channels();
for (i = next_channel;; i = (i + 1) % migrate_multifd_channels()) {
p = &multifd_send_state->params[i];
qemu_mutex_lock(&p->mutex);
if (p->quit) {
error_report("%s: channel %d has already quit!", __func__, i);
qemu_mutex_unlock(&p->mutex);
if (multifd_send_should_exit()) {
return -1;
}
p = &multifd_send_state->params[i];
qemu_mutex_lock(&p->mutex);
if (!p->pending_job) {
p->pending_job++;
next_channel = (i + 1) % migrate_multifd_channels();
@ -483,6 +485,16 @@ static void multifd_send_terminate_threads(Error *err)
{
int i;
/*
* We don't want to exit each threads twice. Depending on where
* we get the error, or if there are two independent errors in two
* threads at the same time, we can end calling this function
* twice.
*/
if (qatomic_xchg(&multifd_send_state->exiting, 1)) {
return;
}
trace_multifd_send_terminate_threads(err != NULL);
if (err) {
@ -497,26 +509,13 @@ static void multifd_send_terminate_threads(Error *err)
}
}
/*
* We don't want to exit each threads twice. Depending on where
* we get the error, or if there are two independent errors in two
* threads at the same time, we can end calling this function
* twice.
*/
if (qatomic_xchg(&multifd_send_state->exiting, 1)) {
return;
}
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
qemu_mutex_lock(&p->mutex);
p->quit = true;
qemu_sem_post(&p->sem);
if (p->c) {
qio_channel_shutdown(p->c, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
}
qemu_mutex_unlock(&p->mutex);
}
}
@ -615,16 +614,13 @@ int multifd_send_sync_main(void)
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
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);
if (multifd_send_should_exit()) {
return -1;
}
trace_multifd_send_sync_main_signal(p->id);
qemu_mutex_lock(&p->mutex);
p->packet_num = multifd_send_state->packet_num++;
p->flags |= MULTIFD_FLAG_SYNC;
p->pending_job++;
@ -634,6 +630,10 @@ int multifd_send_sync_main(void)
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (multifd_send_should_exit()) {
return -1;
}
qemu_sem_wait(&multifd_send_state->channels_ready);
trace_multifd_send_sync_main_wait(p->id);
qemu_sem_wait(&p->sem_sync);
@ -671,7 +671,7 @@ static void *multifd_send_thread(void *opaque)
qemu_sem_post(&multifd_send_state->channels_ready);
qemu_sem_wait(&p->sem);
if (qatomic_read(&multifd_send_state->exiting)) {
if (multifd_send_should_exit()) {
break;
}
qemu_mutex_lock(&p->mutex);
@ -786,12 +786,7 @@ static void multifd_tls_outgoing_handshake(QIOTask *task,
trace_multifd_tls_outgoing_handshake_error(ioc, error_get_pretty(err));
migrate_set_error(migrate_get_current(), err);
/*
* Error happen, mark multifd_send_thread status as 'quit' although it
* is not created, and then tell who pay attention to me.
*/
p->quit = true;
multifd_send_terminate_threads(err);
multifd_send_kick_main(p);
error_free(err);
}
@ -857,22 +852,6 @@ static bool multifd_channel_connect(MultiFDSendParams *p,
return true;
}
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 */
multifd_send_kick_main(p);
/*
* 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;
object_unref(OBJECT(ioc));
error_free(err);
}
static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
{
MultiFDSendParams *p = opaque;
@ -889,7 +868,10 @@ static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
}
trace_multifd_new_send_channel_async_error(p->id, local_err);
multifd_new_send_channel_cleanup(p, ioc, local_err);
multifd_send_terminate_threads(local_err);
multifd_send_kick_main(p);
object_unref(OBJECT(ioc));
error_free(local_err);
}
static void multifd_new_send_channel_create(gpointer opaque)
@ -921,7 +903,6 @@ int multifd_save_setup(Error **errp)
qemu_mutex_init(&p->mutex);
qemu_sem_init(&p->sem, 0);
qemu_sem_init(&p->sem_sync, 0);
p->quit = false;
p->pending_job = 0;
p->id = i;
p->pages = multifd_pages_init(page_count);

2
migration/multifd.h
View File

@ -95,8 +95,6 @@ typedef struct {
QemuMutex mutex;
/* is this channel thread running */
bool running;
/* should this thread finish */
bool quit;
/* multifd flags for each packet */
uint32_t flags;
/* global number of generated multifd packets */