@@ -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
@@ -109,6 +110,16 @@ 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
@@ -45,11 +45,12 @@ VECTOR reserved ; Reserved slots
VECTOR handle_interrupt ; (16) Timer0
VECTOR handle_interrupt ; unused (Timer1)
VECTOR handle_interrupt ; unused (WDT)
-VECTOR handle_interrupt ; (19) ICI (inter core interrupt)
-VECTOR handle_interrupt
-VECTOR handle_interrupt
-VECTOR handle_interrupt
-VECTOR handle_interrupt ; (23) End of fixed IRQs
+VECTOR handle_interrupt ; (19) Inter core Interrupt (IPI)
+VECTOR handle_interrupt ; (20) perf Interrupt
+VECTOR handle_interrupt ; (21) Software Triggered Intr (Self IPI)
+VECTOR handle_interrupt ; unused
+VECTOR handle_interrupt ; (23) unused
+# End of fixed IRQs
.rept CONFIG_ARC_NUMBER_OF_INTERRUPTS - 8
VECTOR handle_interrupt
@@ -11,8 +11,11 @@
#include <linux/smp.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
+#include <asm/irqflags-arcv2.h>
#include <asm/mcip.h>
+#define SOFTIRQ_IRQ 21
+
static char smp_cpuinfo_buf[128];
static int idu_detected;
@@ -28,6 +31,7 @@ static DEFINE_RAW_SPINLOCK(mcip_lock);
void mcip_init_smp(unsigned int cpu)
{
smp_ipi_irq_setup(cpu, IPI_IRQ);
+ smp_ipi_irq_setup(cpu, SOFTIRQ_IRQ);
}
static void mcip_ipi_send(int cpu)
@@ -35,6 +39,12 @@ 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
@@ -69,6 +79,11 @@ 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 */
This is a note to let you know that I have just added a patch titled ARCv2: SMP: Emulate IPI to self using software triggered interrupt to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue This patch is scheduled to be released in version 4.2.8-ckt5. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 4.2.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 895a9f690313a2bb99a3f0f16b7030605caeed9e Mon Sep 17 00:00:00 2001 From: Vineet Gupta <vgupta@synopsys.com> Date: Tue, 23 Feb 2016 11:55:16 +0530 Subject: ARCv2: SMP: Emulate IPI to self using software triggered interrupt commit bb143f814ea488769ca2e79e0b376139cb5f134b upstream. 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> Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/arc/include/asm/irqflags-arcv2.h | 11 +++++++++++ arch/arc/kernel/entry-arcv2.S | 11 ++++++----- arch/arc/kernel/mcip.c | 15 +++++++++++++++ 3 files changed, 32 insertions(+), 5 deletions(-) -- 2.7.0