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authorDaniel Thompson <daniel.thompson@linaro.org>2014-11-26 10:51:52 +0000
committerDaniel Thompson <daniel.thompson@linaro.org>2016-06-21 15:45:41 +0100
commit0bc7c8fd60420c66a1dd60668570c5a82596387d (patch)
tree4a56605c9960710c012936eec66a5b6bac8e396f
parent9ea34127af766fe5451db3edbc5ab9c26abf2399 (diff)
downloadlinux-0bc7c8fd60420c66a1dd60668570c5a82596387d.tar.gz
irqchip: gic: Make gic_raise_softirq FIQ-safe
It is currently possible for FIQ handlers to re-enter gic_raise_softirq() and lock up. gic_raise_softirq() lock(x); -~-> FIQ handle_fiq() gic_raise_softirq() lock(x); <-- Lockup arch/arm/ uses IPIs to implement arch_irq_work_raise(), thus this issue renders it difficult for FIQ handlers to safely defer work to less restrictive calling contexts. This patch fixes the problem by converting the cpu_map_migration_lock into a rwlock making it safe to re-enter the function. Note that having made it safe to re-enter gic_raise_softirq() we no longer need to mask interrupts during gic_raise_softirq() because the b.L migration is always performed from task context. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jason Cooper <jason@lakedaemon.net> Cc: Russell King <linux@arm.linux.org.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
-rw-r--r--drivers/irqchip/irq-gic.c38
1 files changed, 25 insertions, 13 deletions
diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index 2c14eb047359..416f352ea6fc 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -96,22 +96,25 @@ static DEFINE_RAW_SPINLOCK(irq_controller_lock);
/*
* This lock is used by the big.LITTLE migration code to ensure no IPIs
* can be pended on the old core after the map has been updated.
+ *
+ * This lock may be locked for reading from both IRQ and FIQ handlers
+ * and therefore must not be locked for writing when these are enabled.
*/
#ifdef CONFIG_BL_SWITCHER
-static DEFINE_RAW_SPINLOCK(cpu_map_migration_lock);
+static DEFINE_RWLOCK(cpu_map_migration_lock);
-static inline void gic_migration_lock(unsigned long *flags)
+static inline void gic_migration_lock(void)
{
- raw_spin_lock_irqsave(&cpu_map_migration_lock, *flags);
+ read_lock(&cpu_map_migration_lock);
}
-static inline void gic_migration_unlock(unsigned long flags)
+static inline void gic_migration_unlock(void)
{
- raw_spin_unlock_irqrestore(&cpu_map_migration_lock, flags);
+ read_unlock(&cpu_map_migration_lock);
}
#else
-static inline void gic_migration_lock(unsigned long *flags) {}
-static inline void gic_migration_unlock(unsigned long flags) {}
+static inline void gic_migration_lock(void) {}
+static inline void gic_migration_unlock(void) {}
#endif
/*
@@ -785,12 +788,20 @@ static int __init gic_pm_init(struct gic_chip_data *gic)
#endif
#ifdef CONFIG_SMP
+/*
+ * Raise the specified IPI on all cpus set in mask.
+ *
+ * This function is safe to call from all calling contexts, including
+ * FIQ handlers. It relies on gic_migration_lock() being multiply acquirable
+ * to avoid deadlocks when the function is re-entered at different
+ * exception levels.
+ */
static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq)
{
int cpu;
- unsigned long flags, map = 0;
+ unsigned long map = 0;
- gic_migration_lock(&flags);
+ gic_migration_lock();
/* Convert our logical CPU mask into a physical one. */
for_each_cpu(cpu, mask)
@@ -805,7 +816,7 @@ 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);
- gic_migration_unlock(flags);
+ gic_migration_unlock();
}
#endif
@@ -853,7 +864,8 @@ int gic_get_cpu_id(unsigned int cpu)
* Migrate all peripheral interrupts with a target matching the current CPU
* to the interface corresponding to @new_cpu_id. The CPU interface mapping
* is also updated. Targets to other CPU interfaces are unchanged.
- * This must be called with IRQs locally disabled.
+ * This must be called from a task context and with IRQ and FIQ locally
+ * disabled.
*/
void gic_migrate_target(unsigned int new_cpu_id)
{
@@ -883,9 +895,9 @@ void gic_migrate_target(unsigned int new_cpu_id)
* pending on the old cpu static. That means we can defer the
* migration until after we have released the irq_controller_lock.
*/
- raw_spin_lock(&cpu_map_migration_lock);
+ write_lock(&cpu_map_migration_lock);
gic_cpu_map[cpu] = 1 << new_cpu_id;
- raw_spin_unlock(&cpu_map_migration_lock);
+ write_unlock(&cpu_map_migration_lock);
/*
* Find all the peripheral interrupts targetting the current