On Fri, Nov 01, 2013 at 03:56:34PM +0100, Peter Zijlstra wrote:
> On Wed, Oct 30, 2013 at 11:40:15PM -0700, Paul E. McKenney wrote:
> > > Now the whole crux of the question is if we need barrier A at all, since
> > > the STORES issued by the @buf writes are dependent on the ubuf->tail
> > > read.
>
On Fri, Nov 01, 2013 at 05:18:19PM +0100, Peter Zijlstra wrote:
> On Wed, Oct 30, 2013 at 11:40:15PM -0700, Paul E. McKenney wrote:
> > The dependency you are talking about is via the "if" statement?
> > Even C/C++11 is not required to respect control dependencies.
> >
> > This one is a bit annoyi
[ Adding David Howells, Lech Fomicki, and Mark Batty on CC for their
thoughts given previous discussions. ]
On Sat, Nov 02, 2013 at 09:36:18AM -0700, Paul E. McKenney wrote:
> On Fri, Nov 01, 2013 at 03:12:58PM +0200, Victor Kaplansky wrote:
> > "Paul E. McKenney" wrote on 10/31/2013
> > 08:16:
On Fri, Nov 01, 2013 at 06:06:58PM +0200, Victor Kaplansky wrote:
> "Paul E. McKenney" wrote on 10/31/2013
> 05:25:43 PM:
>
> > I really don't care about "fair" -- I care instead about the kernel
> > working reliably.
>
> Though I don't see how putting a memory barrier without deep understanding
On Fri, Nov 01, 2013 at 11:30:17AM +0100, Peter Zijlstra wrote:
> On Fri, Nov 01, 2013 at 02:28:14AM -0700, Paul E. McKenney wrote:
> > > This is a completely untenable position.
> >
> > Indeed it is!
> >
> > C/C++ never was intended to be used for parallel programming,
>
> And yet pretty much
On Fri, Nov 01, 2013 at 03:12:58PM +0200, Victor Kaplansky wrote:
> "Paul E. McKenney" wrote on 10/31/2013
> 08:16:02 AM:
>
> > > BTW, it is why you also don't need ACCESS_ONCE() around @tail, but only
> > > around
> > > @head read.
>
> Just to be sure, that we are talking about the same code -
On Fri, Nov 01, 2013 at 04:25:42PM +0200, Victor Kaplansky wrote:
> "Paul E. McKenney" wrote on 10/31/2013
> 08:40:15 AM:
>
> > > void ubuf_read(void)
> > > {
> > >u64 head, tail;
> > >
> > >tail = ACCESS_ONCE(ubuf->tail);
> > >head = ACCESS_ONCE(ubuf->head);
> > >
> > >/*
> > >
On Fri, Nov 01, 2013 at 05:11:29PM +0100, Peter Zijlstra wrote:
> On Wed, Oct 30, 2013 at 11:40:15PM -0700, Paul E. McKenney wrote:
> > > void kbuf_write(int sz, void *buf)
> > > {
> > > u64 tail = ACCESS_ONCE(ubuf->tail); /* last location userspace read */
> > > u64 offset = kbuf->head; /* we
On Fri, 04 Oct 2013 11:42:49 +0100, Sudeep KarkadaNagesha
wrote:
> Hi Grant,
>
> On 18/09/13 17:18, Sudeep KarkadaNagesha wrote:
> > On 18/09/13 15:51, Grant Likely wrote:
> >> On Wed, 18 Sep 2013 11:53:03 +0100, Sudeep KarkadaNagesha
> >> wrote:
> >>> From: Sudeep KarkadaNagesha
> >>>
> >>>
