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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: 2dcf75e279 ("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>
This commit is contained in:
Gregory CLEMENT 2016-02-04 22:09:24 +01:00 committed by David S. Miller
parent 129219e495
commit cad5d847a0
1 changed files with 9 additions and 4 deletions
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13
drivers/net/ethernet/marvell/mvneta.c
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@ -2849,9 +2849,14 @@ static void mvneta_percpu_disable(void *arg)
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) {
@ -2862,7 +2867,7 @@ static void mvneta_percpu_elect(struct mvneta_port *pp)
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
*/
@ -2873,7 +2878,7 @@ static void mvneta_percpu_elect(struct mvneta_port *pp)
* 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)) &