On 12/29, Manfred Spraul wrote: > > >I think that your patch (and the original patch from WangYuli) has the same > >proble with pipe_poll()->poll_wait()->__pollwait(). > > What is the memory barrier for pipe_poll()? > > There is poll_wait()->__pollwait()->add_wait_queue()->spin_unlock(). thus > only store_release. > > And then READ_ONCE(), i.e. no memory barrier. > > Thus the CPU would be free to load pipe->head and pipe->tail before adding > the entry to the poll table. > > Correct? Yes, this was my thinking. See also my initial reply to WangYuli https://lore.kernel.org/all/20241226160007.GA11118@xxxxxxxxxx/ Do you agree? Oleg.
