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migration: fix migrate_cancel leads live_migration thread endless loop 

When we 'migrate_cancel' a multifd migration, live_migration thread may
go into endless loop in multifd_send_pages functions.

Reproduce steps:

(qemu) migrate_set_capability multifd on
(qemu) migrate -d url
(qemu) [wait a while]
(qemu) migrate_cancel

Then may get live_migration 100% cpu usage in following stack:

pthread_mutex_lock
qemu_mutex_lock_impl
multifd_send_pages
multifd_queue_page
ram_save_multifd_page
ram_save_target_page
ram_save_host_page
ram_find_and_save_block
ram_find_and_save_block
ram_save_iterate
qemu_savevm_state_iterate
migration_iteration_run
migration_thread
qemu_thread_start
start_thread
clone

Signed-off-by: Ivan Ren <ivanren@tencent.com>
Message-Id: <1561468699-9819-2-git-send-email-ivanren@tencent.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
master
Ivan Ren 2019-06-25 21:18:17 +08:00 committed by Juan Quintela
parent bf8b024372
commit 713f762a31
1 changed files with 29 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
migration/ram.c
View File

@ -920,7 +920,7 @@ struct {
* false.
*/
static void multifd_send_pages(void)
static int multifd_send_pages(void)
{
int i;
static int next_channel;
@ -933,6 +933,11 @@ static void multifd_send_pages(void)
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);
return -1;
}
if (!p->pending_job) {
p->pending_job++;
next_channel = (i + 1) % migrate_multifd_channels();
@ -951,9 +956,11 @@ static void multifd_send_pages(void)
ram_counters.transferred += transferred;;
qemu_mutex_unlock(&p->mutex);
qemu_sem_post(&p->sem);
return 1;
}
static void multifd_queue_page(RAMBlock *block, ram_addr_t offset)
static int multifd_queue_page(RAMBlock *block, ram_addr_t offset)
{
MultiFDPages_t *pages = multifd_send_state->pages;
@ -968,15 +975,19 @@ static void multifd_queue_page(RAMBlock *block, ram_addr_t offset)
pages->used++;
if (pages->used < pages->allocated) {
return;
return 1;
}
}
multifd_send_pages();
if (multifd_send_pages() < 0) {
return -1;
}
if (pages->block != block) {
multifd_queue_page(block, offset);
return multifd_queue_page(block, offset);
}
return 1;
}
static void multifd_send_terminate_threads(Error *err)
@ -1049,7 +1060,10 @@ static void multifd_send_sync_main(void)
return;
}
if (multifd_send_state->pages->used) {
multifd_send_pages();
if (multifd_send_pages() < 0) {
error_report("%s: multifd_send_pages fail", __func__);
return;
}
}
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
@ -1058,6 +1072,12 @@ static void multifd_send_sync_main(void)
qemu_mutex_lock(&p->mutex);
if (p->quit) {
error_report("%s: channel %d has already quit", __func__, i);
qemu_mutex_unlock(&p->mutex);
return;
}
p->packet_num = multifd_send_state->packet_num++;
p->flags |= MULTIFD_FLAG_SYNC;
p->pending_job++;
@ -2033,7 +2053,9 @@ static int ram_save_page(RAMState *rs, PageSearchStatus *pss, bool last_stage)
static int ram_save_multifd_page(RAMState *rs, RAMBlock *block,
ram_addr_t offset)
{
multifd_queue_page(block, offset);
if (multifd_queue_page(block, offset) < 0) {
return -1;
}
ram_counters.normal++;
return 1;