From e0af22d9fd16d1cc2910a68d204e1767be2f8f14 Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Thu, 22 Jun 2017 14:23:18 +0200 Subject: [PATCH] net: mvpp2: add comments about smp_processor_id() usage A previous commit modified a number of smp_processor_id() used in migration-enabled contexts into get_cpu/put_cpu sections. However, a few smp_processor_id() calls remain in the driver, and this commit adds comments explaining why they can be kept. Signed-off-by: Thomas Petazzoni Signed-off-by: David S. Miller --- drivers/net/ethernet/marvell/mvpp2.c | 33 ++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/marvell/mvpp2.c b/drivers/net/ethernet/marvell/mvpp2.c index ca4b55c60682..4b3bf37c8038 100644 --- a/drivers/net/ethernet/marvell/mvpp2.c +++ b/drivers/net/ethernet/marvell/mvpp2.c @@ -4162,7 +4162,10 @@ static inline void mvpp2_interrupts_disable(struct mvpp2_port *port) MVPP2_ISR_DISABLE_INTERRUPT(cpu_mask)); } -/* Mask the current CPU's Rx/Tx interrupts */ +/* Mask the current CPU's Rx/Tx interrupts + * Called by on_each_cpu(), guaranteed to run with migration disabled, + * using smp_processor_id() is OK. + */ static void mvpp2_interrupts_mask(void *arg) { struct mvpp2_port *port = arg; @@ -4171,7 +4174,10 @@ static void mvpp2_interrupts_mask(void *arg) MVPP2_ISR_RX_TX_MASK_REG(port->id), 0); } -/* Unmask the current CPU's Rx/Tx interrupts */ +/* Unmask the current CPU's Rx/Tx interrupts. + * Called by on_each_cpu(), guaranteed to run with migration disabled, + * using smp_processor_id() is OK. + */ static void mvpp2_interrupts_unmask(void *arg) { struct mvpp2_port *port = arg; @@ -4554,7 +4560,11 @@ mvpp2_txq_next_desc_get(struct mvpp2_tx_queue *txq) return txq->descs + tx_desc; } -/* Update HW with number of aggregated Tx descriptors to be sent */ +/* Update HW with number of aggregated Tx descriptors to be sent + * + * Called only from mvpp2_tx(), so migration is disabled, using + * smp_processor_id() is OK. + */ static void mvpp2_aggr_txq_pend_desc_add(struct mvpp2_port *port, int pending) { /* aggregated access - relevant TXQ number is written in TX desc */ @@ -4565,6 +4575,9 @@ static void mvpp2_aggr_txq_pend_desc_add(struct mvpp2_port *port, int pending) /* Check if there are enough free descriptors in aggregated txq. * If not, update the number of occupied descriptors and repeat the check. + * + * Called only from mvpp2_tx(), so migration is disabled, using + * smp_processor_id() is OK. */ static int mvpp2_aggr_desc_num_check(struct mvpp2 *priv, struct mvpp2_tx_queue *aggr_txq, int num) @@ -4583,7 +4596,12 @@ static int mvpp2_aggr_desc_num_check(struct mvpp2 *priv, return 0; } -/* Reserved Tx descriptors allocation request */ +/* Reserved Tx descriptors allocation request + * + * Called only from mvpp2_txq_reserved_desc_num_proc(), itself called + * only by mvpp2_tx(), so migration is disabled, using + * smp_processor_id() is OK. + */ static int mvpp2_txq_alloc_reserved_desc(struct mvpp2 *priv, struct mvpp2_tx_queue *txq, int num) { @@ -4687,6 +4705,10 @@ static u32 mvpp2_txq_desc_csum(int l3_offs, int l3_proto, /* Get number of sent descriptors and decrement counter. * The number of sent descriptors is returned. * Per-CPU access + * + * Called only from mvpp2_txq_done(), called from mvpp2_tx() + * (migration disabled) and from the TX completion tasklet (migration + * disabled) so using smp_processor_id() is OK. */ static inline int mvpp2_txq_sent_desc_proc(struct mvpp2_port *port, struct mvpp2_tx_queue *txq) @@ -4701,6 +4723,9 @@ static inline int mvpp2_txq_sent_desc_proc(struct mvpp2_port *port, MVPP2_TRANSMITTED_COUNT_OFFSET; } +/* Called through on_each_cpu(), so runs on all CPUs, with migration + * disabled, therefore using smp_processor_id() is OK. + */ static void mvpp2_txq_sent_counter_clear(void *arg) { struct mvpp2_port *port = arg; -- 2.20.1