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[Qemu-devel] [PATCH 1/4] migration: fix migrate_cancel leads live_migrat
From: |
Juan Quintela |
Subject: |
[Qemu-devel] [PATCH 1/4] migration: fix migrate_cancel leads live_migration thread endless loop |
Date: |
Wed, 24 Jul 2019 11:55:20 +0200 |
From: Ivan Ren <address@hidden>
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 <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Juan Quintela <address@hidden>
Signed-off-by: Juan Quintela <address@hidden>
---
migration/ram.c | 36 +++++++++++++++++++++++++++++-------
1 file changed, 29 insertions(+), 7 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 2b0774c2bf..52a2d498e4 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -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;
--
2.21.0