Messages in this thread | | | Date | Tue, 25 Jul 2017 15:29:45 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring buffer overwrite |
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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@infradead.org> 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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