Messages in this thread |  | | Date | Wed, 18 Feb 2015 17:11:12 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/2] [PATCH] sched: Add smp_rmb() in task rq locking cycles |
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On Wed, Feb 18, 2015 at 04:53:34PM +0100, Oleg Nesterov wrote: > On 02/17, Paul E. McKenney wrote: > > > > | mb | wmb | rmb | rbd | acq | rel | ctl | > > -----+-------+-------+-------+-------+-------+-------+-------+ > > mb | Y | | Y | y | Y | | Y + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > wmb | Y | | Y | y | Y | | Y + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > rmb | | | | | | | + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > rbd | | | | | | | + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > acq | | | | | | | + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > rel | Y | | Y | y | Y | | Y + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > ctl | | | | | | | + > > -----+-------+-------+-------+-------+-------+-------+-------+ > > OK, so "acq" can't pair with "acq", and I am not sure I understand.
Please consider the table in the context of message passing; that is what Paul proposed. Your example from sysvsems, while interesting, would not fit the general scenario of message passing.
This too illustrates a problem with that approach, people can't read, so they'll pick the wrong table to look at.
I really think having just the _one_ table with obvious pairings marked, and everything not marked in the table needs careful reading.
And acq-acq pairing would be a careful one in my book.
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