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- From: Gregory CLEMENT <gregory.clement@free-electrons.com>
- 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 <gregory.clement@free-electrons.com>
- Signed-off-by: David S. Miller <davem@davemloft.net>
- ---
- --- 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)) &
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