From: Gregory CLEMENT Date: Thu, 4 Feb 2016 22:09:24 +0100 Subject: [PATCH] net: mvneta: Fix the CPU choice in mvneta_percpu_elect When passing to the management of multiple RX queue, the mvneta_percpu_elect function was broken. The use of the modulo can lead to elect the wrong cpu. For example with rxq_def=2, if the CPU 2 goes offline and then online, we ended with the third RX queue activated in the same time on CPU 0 and CPU2, which lead to a kernel crash. With this fix, we don't try to get "the closer" CPU if the default CPU is gone, now we just use CPU 0 which always be there. Thanks to this, the code becomes more readable, easier to maintain and more predicable. Cc: stable@vger.kernel.org Fixes: 2dcf75e2793c ("net: mvneta: Associate RX queues with each CPU") Signed-off-by: Gregory CLEMENT Signed-off-by: David S. Miller --- --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -2851,9 +2851,14 @@ static void mvneta_percpu_disable(void * static void mvneta_percpu_elect(struct mvneta_port *pp) { - int online_cpu_idx, max_cpu, cpu, i = 0; + int elected_cpu = 0, max_cpu, cpu, i = 0; + + /* Use the cpu associated to the rxq when it is online, in all + * the other cases, use the cpu 0 which can't be offline. + */ + if (cpu_online(pp->rxq_def)) + elected_cpu = pp->rxq_def; - online_cpu_idx = pp->rxq_def % num_online_cpus(); max_cpu = num_present_cpus(); for_each_online_cpu(cpu) { @@ -2864,7 +2869,7 @@ static void mvneta_percpu_elect(struct m if ((rxq % max_cpu) == cpu) rxq_map |= MVNETA_CPU_RXQ_ACCESS(rxq); - if (i == online_cpu_idx) + if (cpu == elected_cpu) /* Map the default receive queue queue to the * elected CPU */ @@ -2875,7 +2880,7 @@ static void mvneta_percpu_elect(struct m * the CPU bound to the default RX queue */ if (txq_number == 1) - txq_map = (i == online_cpu_idx) ? + txq_map = (cpu == elected_cpu) ? MVNETA_CPU_TXQ_ACCESS(1) : 0; else txq_map = mvreg_read(pp, MVNETA_CPU_MAP(cpu)) &