On Thu, May 21, 2015 at 11:49:21AM +0800, Herbert Xu wrote: > The timer operations are all supposed to be idempotent. So enabling > a port twice or stopping it twice should be OK. Oki doki. > > > * Might calls to br_multicast_add_router() via br_multicast_enable_port() > > cause unintended side-effects? > > What do you mean? How does add_router get called from enable_port? Sorry, ment br_multicast_add_router() via br_multicast_set_port_router(). But it's not modifying any timers, and other modifications are locked by the multicast lock, right. > See above. It's there so that you don't readd a timer when we're > calling del_timer_sync. del_timer_sync has to be called without > the multicast lock so that's why we need another mechanism to > prevent the timers from being readded. Right, all the touched functions never rearm a timer. The multicast_router timer may only get readded upon receiving a multicast query. (br_multicast_query_received()->br_multicast_mark_router() ) By removing the netif_running check we might only delete a timer which wasn't running anyway which as you said already is safe. > > AFAICS the spots you patched aren't adding timers so they *should* > be OK. Okay, thanks for your thorough explanations about the timers and how the locking is supposed to work. After your explanations I went over the code a few more times and am fairly confident too now, that this patch is supposed to work fine. Going to resend this patch without the RFC tag. Cheers, Linus
