vhost memory hotplug deadlock

PATCH Stephen Hemminger 1 participant 1 message Sep 19, 2018 Network drivers

Share & tools

Stephen Hemminger

author

2018-09-19 19:10 UTC #0 lore raw

The Vhost memory handling will self deadlock.

The sequence is:
rte_zmalloc
malloc_heap_alloc
heap_alloc_on_socket
alloc_more_mem_on_socket
try_expand_heap_primary

Acquires memory_hotplug_lock for write

eal_memalloc_mem_event_notify
vhost_user_mem_event_cb
vhost_kernel_ioctl
rte_memseg_contig_walk

Deadlocks acquiring memory_hotplug_lock for read

The following may fix it.

drivers/net/virtio/virtio_user/vhost_kernel.c +2 -1

index d1be82162609..549235df0ca2 100644
@@ -115,7 +115,8 @@ prepare_vhost_memory_kernel(void)
        wa.region_nr = 0;
        wa.vm = vm;
 
-       if (rte_memseg_contig_walk(add_memory_region, &wa) < 0) {
+       /* memory_hotplug_lock already held  */
+       if (rte_memseg_contig_walk_thread_unsafe(add_memory_region, &wa) < 0) {
                free(vm);
                return NULL;
        }