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multifd: Fix a race on reading MultiFDPages_t.block 

In multifd_queue_page() MultiFDPages_t.block is checked twice.
Between the two checks, MultiFDPages_t.block may be reset to NULL
by multifd thread. This lead to the 2nd check always true then a
redundant page submitted to multifd thread again.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
master
Zhenzhong Duan 2022-10-17 15:53:50 +08:00 committed by Juan Quintela
parent 6720c2b327
commit ddbe628c97
1 changed files with 5 additions and 2 deletions
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7
migration/multifd.c
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@ -442,6 +442,7 @@ static int multifd_send_pages(QEMUFile *f)
int multifd_queue_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset)
{
MultiFDPages_t *pages = multifd_send_state->pages;
bool changed = false;
if (!pages->block) {
pages->block = block;
@ -454,14 +455,16 @@ int multifd_queue_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset)
if (pages->num < pages->allocated) {
return 1;
}
} else {
changed = true;
}
if (multifd_send_pages(f) < 0) {
return -1;
}
if (pages->block != block) {
return multifd_queue_page(f, block, offset);
if (changed) {
return multifd_queue_page(f, block, offset);
}
return 1;