[PATCH] irqchip: gic: Allow gic_arch_extn hooks to call into scheduler

On 08/04/14 16:20, Nicolas Pitre wrote:

On Mon, 4 Aug 2014, Stephen Boyd wrote:

quoted

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index 7c131cf7cc13..824c1e2ac403 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c

@@ -72,6 +72,8 @@ struct gic_chip_data {
 };
 
 static DEFINE_RAW_SPINLOCK(irq_controller_lock);
+/* Synchronize switching CPU interface and sending SGIs */
+static DEFINE_RAW_SPINLOCK(gic_sgi_lock);

I'd suggest moving this below gic_cpu_map[] definition for the comment 
block right above it to also apply to this lock.

Ok.

quoted

 
 /*
  * The GIC mapping of CPU interfaces does not necessarily match

@@ -658,7 +660,7 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq)
 	int cpu;
 	unsigned long flags, map = 0;
 
-	raw_spin_lock_irqsave(&irq_controller_lock, flags);
+	raw_spin_lock_irqsave(&gic_sgi_lock, flags);
 
 	/* Convert our logical CPU mask into a physical one. */
 	for_each_cpu(cpu, mask)

@@ -673,7 +675,7 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq)
 	/* this always happens on GIC0 */
 	writel_relaxed(map << 16 | irq, gic_data_dist_base(&gic_data[0]) + GIC_DIST_SOFTINT);
 
-	raw_spin_unlock_irqrestore(&irq_controller_lock, flags);
+	raw_spin_unlock_irqrestore(&gic_sgi_lock, flags);
 }
 #endif
 

@@ -742,6 +744,7 @@ void gic_migrate_target(unsigned int new_cpu_id)
 	cur_target_mask = 0x01010101 << cur_cpu_id;
 	ror_val = (cur_cpu_id - new_cpu_id) & 31;
 
+	raw_spin_lock(&gic_sgi_lock);
 	raw_spin_lock(&irq_controller_lock);

According to your call trace, you would now take irq_controller_lock and 
then gic_sgi_lock.  Here you're doing it in the opposite order with an 
AB-BA deadlock potential.  I'd suggest reversing them here.

Ah thanks. I guess I didn't see it on lockdep because this code never
runs. Actually I don't think we need to hold it across this piece of
code at all. See v2.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation