On Fri, Jul 21, 2017 at 03:54:20PM +0200, Peter Zijlstra wrote:
> On Fri, Jul 14, 2017 at 03:42:10PM +0900, Byungchul Park wrote:
> > On Thu, Jul 13, 2017 at 08:23:33PM +0900, Byungchul Park wrote:
> > > On Thu, Jul 13, 2017 at 8:12 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > > > On Thu, Jul 13, 2017 at 12:29:05PM +0200, Peter Zijlstra wrote:
> > > >> On Thu, Jul 13, 2017 at 07:09:53PM +0900, Byungchul Park wrote:
> > > >> > On Thu, Jul 13, 2017 at 11:50:52AM +0200, Peter Zijlstra wrote:
> > > >> > > wait_for_completion(&C);
> > > >> > > atomic_inc_return();
> > > >> > >
> > > >> > > mutex_lock(A1);
> > > >> > > mutex_unlock(A1);
> > > >> > >
> > > >> > >
> > > >> > > <IRQ>
> > > >> > > spin_lock(B1);
> > > >> > > spin_unlock(B1);
> > > >> > >
> > > >> > > ...
> > > >> > >
> > > >> > > spin_lock(B64);
> > > >> > > spin_unlock(B64);
> > > >> > > </IRQ>
> > > >> > >
> > > >> > >
> > > >
> > > > Also consider the alternative:
> > > >
> > > > <IRQ>
> > > > spin_lock(D);
> > > > spin_unlock(D);
> > > >
> > > > complete(&C);
> > > > </IRQ>
> > > >
> > > > in which case the context test will also not work.
> > >
> > > Context tests are done on xhlock with the release context, _not_
> > > acquisition context. For example, spin_lock(D) and complete(&C) are
> > > in the same context, so the test would pass in this example.
>
> The point was, this example will also link C to B*.
_No_, as I already said.
> (/me copy paste from older email)
>
> That gives:
>
> xhist[ 0] = A1
> xhist[ 1] = B1
> ...
> xhist[63] = B63
>
> then we wrap and have:
>
> xhist[0] = B64
>
> then we rewind to 1 and invalidate to arrive at:
We invalidate xhist[_0_], as I already said.
> xhist[ 0] = B64
> xhist[ 1] = NULL <-- idx
> xhist[ 2] = B2
> ...
> xhist[63] = B63
>
>
> Then we do D and get
>
> xhist[ 0] = B64
> xhist[ 1] = D <-- idx
> xhist[ 2] = B2
> ...
> xhist[63] = B63
We should get
xhist[ 0] = NULL
xhist[ 1] = D <-- idx
xhist[ 2] = B2
...
xhist[63] = B63
By the way, did not you get my reply? I did exactly same answer.
Perhaps You have not received or read my replies.
> And now there is nothing that will invalidate B*, after all, the
> gen_id's are all after C's stamp, and the same_context_xhlock() test
> will also pass because they're all from IRQ context (albeit not the
> same, but it cannot tell).
It will stop at xhist[0] because it has been invalidated.
> Does this explain? Or am I still missing something?
Could you read the following reply? Not enough?
https://lkml.org/lkml/2017/7/13/214
I am sorry if my english makes you hard to understand. But I already
answered all you asked.
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