From: Al Viro <v...@zeniv.linux.org.uk>
Date: Sun, 4 Dec 2016 21:04:55 +0000
> Could we please kill that kludge? "af_unix: use freezable blocking
> calls in read" had been wrong to start with; having a method make assumptions
> of that sort ("nobody will call me while holding locks I hadn't thought of")
> is asking for serious trouble. splice is just a place where lockdep has
> caught that - we *can't* assume that nobody will ever call kernel_recvmsg()
> while holding some locks.
>
> I've run into that converting AF_UNIX to generic_file_splice_read();
> I can kludge around that ("freezable unless ->msg_iter is ITER_PIPE"), but
> that only delays trouble.
>
> Note that the only other user of freezable_schedule_timeout() is
> a very different story - it's a kernel thread, which *does* have a guaranteed
> locking environment. Making such assumptions in unix_stream_recvmsg(),
> OTOH, is insane...
We have to otherwise Android phones drain their batteries in 10
minutes.
I'm not going to revert this and be responsible for that.
So you have to find a way to make the freezable calls legitimate.
