@@ -22,6 +22,7 @@
#define AUX_IRQ_CTRL 0x00E
#define AUX_IRQ_ACT 0x043 /* Active Intr across all levels */
#define AUX_IRQ_LVL_PEND 0x200 /* Pending Intr across all levels */
+#define AUX_IRQ_HINT 0x201 /* For generating Soft Interrupts */
#define AUX_IRQ_PRIORITY 0x206
#define ICAUSE 0x40a
#define AUX_IRQ_SELECT 0x40b
@@ -115,6 +116,16 @@ static inline int arch_irqs_disabled(void)
return arch_irqs_disabled_flags(arch_local_save_flags());
}
+static inline void arc_softirq_trigger(int irq)
+{
+ write_aux_reg(AUX_IRQ_HINT, irq);
+}
+
+static inline void arc_softirq_clear(int irq)
+{
+ write_aux_reg(AUX_IRQ_HINT, 0);
+}
+
#else
.macro IRQ_DISABLE scratch
@@ -11,9 +11,12 @@
#include <linux/smp.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
+#include <asm/irqflags-arcv2.h>
#include <asm/mcip.h>
#include <asm/setup.h>
+#define SOFTIRQ_IRQ 21
+
static char smp_cpuinfo_buf[128];
static int idu_detected;
@@ -22,6 +25,7 @@ static DEFINE_RAW_SPINLOCK(mcip_lock);
static void mcip_setup_per_cpu(int cpu)
{
smp_ipi_irq_setup(cpu, IPI_IRQ);
+ smp_ipi_irq_setup(cpu, SOFTIRQ_IRQ);
}
static void mcip_ipi_send(int cpu)
@@ -29,6 +33,12 @@ static void mcip_ipi_send(int cpu)
unsigned long flags;
int ipi_was_pending;
+ /* ARConnect can only send IPI to others */
+ if (unlikely(cpu == raw_smp_processor_id())) {
+ arc_softirq_trigger(SOFTIRQ_IRQ);
+ return;
+ }
+
/*
* NOTE: We must spin here if the other cpu hasn't yet
* serviced a previous message. This can burn lots
@@ -63,6 +73,11 @@ static void mcip_ipi_clear(int irq)
unsigned long flags;
unsigned int __maybe_unused copy;
+ if (unlikely(irq == SOFTIRQ_IRQ)) {
+ arc_softirq_clear(irq);
+ return;
+ }
+
raw_spin_lock_irqsave(&mcip_lock, flags);
/* Who sent the IPI */
ARConnect/MCIP Inter-Core-Interrupt module can't send interrupt to local core. So use core intc capability to trigger software interrupt to self, using an unsued IRQ #21. This showed up as csd deadlock with LTP trace_sched on a dual core system. This test acts as scheduler fuzzer, triggering all sorts of schedulting activity. Trouble starts with IPI to self, which doesn't get delivered (effectively lost due to H/w capability), but the msg intended to be sent remain enqueued in per-cpu @ipi_data. All subsequent IPIs to this core from other cores get elided due to the IPI coalescing optimization in ipi_send_msg_one() where a pending msg implies an IPI already sent and assumes other core is yet to ack it. After the elided IPI, other core simply goes into csd_lock_wait() but never comes out as this core never sees the interrupt. Fixes STAR 9001008624 Cc: Peter Zijlstra <peterz@infradead.org> Cc: <stable@vger.kernel.org> [4.2] Signed-off-by: Vineet Gupta <vgupta@synopsys.com> --- arch/arc/include/asm/irqflags-arcv2.h | 11 +++++++++++ arch/arc/kernel/mcip.c | 15 +++++++++++++++ 2 files changed, 26 insertions(+)