[lttng-dev] question about rcu_bp_exit()

[songxin]

Hi,
Now I get a crash because receiving signal SIGSEGV as below.


 #0  arena_alloc (arena=<optimized out>) at /usr/src/debug/liburcu/0.9.1+git5fd33b1e5003ca316bd314ec3fd1447f6199a282-r0/git/urcu-bp.c:432
#1  add_thread () at /usr/src/debug/liburcu/0.9.1+git5fd33b1e5003ca316bd314ec3fd1447f6199a282-r0/git/urcu-bp.c:462

#2  rcu_bp_register () at /usr/src/debug/liburcu/0.9.1+git5fd33b1e5003ca316bd314ec3fd1447f6199a282-r0/git/urcu-bp.c:541


I read the code of urcu-bp.c and found  that  "if (chunk->data_len - chunk->used < len)" is in 432 line. So I guess that the chunk is a illegal pointer.
Below is the function rcu_bp_exit().


static
void rcu_bp_exit(void)
{
        mutex_lock(&init_lock);
        if (!--rcu_bp_refcount) {
                struct registry_chunk *chunk, *tmp;
                int ret;


                cds_list_for_each_entry_safe(chunk, tmp,
                                &registry_arena.chunk_list, node) {
                        munmap(chunk, chunk->data_len
                                        + sizeof(struct registry_chunk));
                }
                ret = pthread_key_delete(urcu_bp_key);
                if (ret)
                        abort();
        }
        mutex_unlock(&init_lock);
}




My question is below.
Why did not delete the chunk from registry_arena.chunk_list before munmap a chunk?


Thanks,
xin

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