This is to workaround the llock/scond livelock HS38x4 could get into a LLOCK/SCOND livelock in case of multiple overlapping coherency transactions in the SCU. The exclusive line state keeps rotating among contenting cores leading to a never ending cycle. So break the cycle by deferring the retry of failed exclusive access (SCOND). The actual delay needed is function of number of contending cores as well as the unrelated coherency traffic from other cores. To keep the code simple, start off with small delay of 1 which would suffice most cases and in case of contention double the delay. Eventually the delay is sufficient such that the coherency pipeline is drained, thus a subsequent exclusive access would succeed. Link: http://lkml.kernel.org/r/1438612568-28265-1-git-send-email-vgupta@synopsys.com Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>