Messages in this thread | | | Date | Wed, 28 Nov 2012 16:38:16 -0800 | From | Zach Brown <> | Subject | Re: [PATCH 14/25] aio: Make aio_read_evt() more efficient |
| |
> We can't use cmpxchg() on the ring buffer's head pointer directly, since > it's modded to nr_events and would be susceptible to ABA. So instead we > maintain a shadow head that uses the full 32 bits, and cmpxchg() that > and then updated the real head pointer.
Time to update this comment to reflect the mutex instead of the shadow head? :)
> + ev = kmap(page); > + copy_ret = copy_to_user(event + ret, ev + pos, sizeof(*ev) * i); > + kunmap(page);
For lack of a better time: do we want to bring up the missing flush_dcache_page() calls around the kernel mappings of ring pages that are also mapped to user addresses?
> prepare_to_wait_exclusive(&ctx->wait, &wait, > TASK_INTERRUPTIBLE); > > + ret = aio_read_events(ctx, event + i, nr - i); > + if (ret < 0) > break;
As mentioned offlist: we don't want to be blocking under TASK_INTERRUPTIBLE. Is the plan to do a non-blocking check and pop outside the wait loop to do a blocking copy?
- z
| |