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> > > > > > > mutex_lock(A2); > > mutex_unlock(A2); > > > > complete(&C); > > > > > > That gives: > > > > xhist[ 0] = A1 > > We have to rollback here later on irq_exit. > > The followings are ones for irq context. > > > xhist[ 1] = B1 > > ... > > xhist[63] = B63 > > > > then we wrap and have: > > > > xhist[0] = B64 > > > > then we rewind to 1 and invalidate to arrive at: > > > > Now, whether xhist[0] has been overwritten or not is important. If yes, > xhist[0] should be NULL, _not_ xhist[1], which is one for irq context so > not interest at all. > > > xhist[ 0] = B64 > > xhist[ 1] = NULL <-- idx > > Therefore, it should be, > > xhist[ 0] = NULL <- invalidate, cannot use it any more > --- <- on returning back from irq context, start from here > xhist[ 1] = B1 <-- obsolete history of irq
Ah, so you rely on the same_context_xhlock() ? That doesn't work for hist (formerly work).
