On Thu, Jun 02, 2011 at 06:23:03PM +0530, Ramkumar Ramachandra wrote:
> On a slightly unrelated note, I just found out that the persist_todo
> can't be called twice due to a lockfile API limitation* -- the
> atexit(3) cleanup handler is supposed to have a linked list of
> lockfiles to clean up. When one lockfile is used twice, it becomes a
> circularly linked list, and the entire program hangs at exit time
> since traversing a circularly linked list is never-ending. Couple of
> comments:
> 1. By reading the lockfile implementation, I understand why this
> happens -- can't it be implemented differently to remove this
> limitation? If not, shouldn't this limitation be documented somewhere?
Doesn't lock_file handle multiple locking already via the on_list parameter?
$ grep -A2 on_list lockfile.c
if (!lk->on_list) {
lk->next = lock_file_list;
lock_file_list = lk;
lk->on_list = 1;
}
However, I think you have a bigger problem, which is that you are
allocating the lock_file on the stack in persist_todo and persist_head.
So by the time the atexit() handler is called, this storage has gone
away and you are just reading random data (not to mention that it also
should be zero-initialized before being passed to lock_file).
-Peff
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