diff options
| -rw-r--r-- | arch/arc/kernel/mcip.c | 27 |
1 files changed, 10 insertions, 17 deletions
diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c index e30d5d428330..7afc3c703ed1 100644 --- a/arch/arc/kernel/mcip.c +++ b/arch/arc/kernel/mcip.c @@ -40,26 +40,19 @@ static void mcip_ipi_send(int cpu) return; } + raw_spin_lock_irqsave(&mcip_lock, flags); + /* - * NOTE: We must spin here if the other cpu hasn't yet - * serviced a previous message. This can burn lots - * of time, but we MUST follows this protocol or - * ipi messages can be lost!!! - * Also, we must release the lock in this loop because - * the other side may get to this same loop and not - * be able to ack -- thus causing deadlock. + * If receiver already has a pending interrupt, elide sending this one. + * Linux cross core calling works well with concurrent IPIs + * coalesced into one + * see arch/arc/kernel/smp.c: ipi_send_msg_one() */ + __mcip_cmd(CMD_INTRPT_READ_STATUS, cpu); + ipi_was_pending = read_aux_reg(ARC_REG_MCIP_READBACK); + if (!ipi_was_pending) + __mcip_cmd(CMD_INTRPT_GENERATE_IRQ, cpu); - do { - raw_spin_lock_irqsave(&mcip_lock, flags); - __mcip_cmd(CMD_INTRPT_READ_STATUS, cpu); - ipi_was_pending = read_aux_reg(ARC_REG_MCIP_READBACK); - if (ipi_was_pending == 0) - break; /* break out but keep lock */ - raw_spin_unlock_irqrestore(&mcip_lock, flags); - } while (1); - - __mcip_cmd(CMD_INTRPT_GENERATE_IRQ, cpu); raw_spin_unlock_irqrestore(&mcip_lock, flags); #ifdef CONFIG_ARC_IPI_DBG |