On Tue, Aug 09, 2011 at 02:11:55PM -0400, Nelson Elhage wrote:
> epoll can acquire recursively acquire ep->mtx on multiple "struct
> eventpoll"s at once in the case where one epoll fd is monitoring
> another epoll fd. This is perfectly OK, since we're careful about the
> lock ordering, but it causes spurious lockdep warnings. Annotate the
> recursion using mutex_lock_nested, and add a comment explaining the
> nesting rules for good measure.
>
> Recent versions of systemd are triggering this, and it can also be
> demonstrated with the following trivial test program:
>
> --------------------8<--------------------
>
> int main(void) {
> int e1, e2;
> struct epoll_event evt = {
> .events = EPOLLIN
> };
>
> e1 = epoll_create1(0);
> e2 = epoll_create1(0);
> epoll_ctl(e1, EPOLL_CTL_ADD, e2, &evt);
> return 0;
> }
> --------------------8<--------------------
>
> Cc: stable@xxxxxxxxxx
> Reported-by: Paul Bolle <pebolle@xxxxxxxxxx>
> Tested-by: Paul Bolle <pebolle@xxxxxxxxxx>
> Signed-off-by: Nelson Elhage <nelhage@xxxxxxxxxxx>
Any progress on this heading upstream?
josh
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