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 > xhist[ 2] = B2 > ... > xhist[63] = B63 > > > Then we do A2 and get > > xhist[ 0] = B64 > xhist[ 1] = A2 <-- idx > xhist[ 2] = B2 > ... > xhist[63] = B63 So invalidating only one is enough. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
