[GIT pull] irq fix for 4.13

[GIT pull] irq fix for 4.13

[Thomas Gleixner]

Linus,

please pull the latest irq-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq-urgent-for-linus


Fix for a regression caused by the conversion of x86 to the generic hotplug
code. Instead of doing a plain single line revert, this adds a pile of
comments so the semantics of the force argument are clear.

Thanks,

	tglx

------------------>
Thomas Gleixner (1):
      genirq/cpuhotplug: Revert "Set force affinity flag on hotplug migration"


 include/linux/irq.h     | 7 ++++++-
 kernel/irq/cpuhotplug.c | 9 +++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 00db35b61e9e..d2d543794093 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -388,7 +388,12 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
  * @irq_mask_ack:	ack and mask an interrupt source
  * @irq_unmask:		unmask an interrupt source
  * @irq_eoi:		end of interrupt
- * @irq_set_affinity:	set the CPU affinity on SMP machines
+ * @irq_set_affinity:	Set the CPU affinity on SMP machines. If the force
+ *			argument is true, it tells the driver to
+ *			unconditionally apply the affinity setting. Sanity
+ *			checks against the supplied affinity mask are not
+ *			required. This is used for CPU hotplug where the
+ *			target CPU is not yet set in the cpu_online_mask.
  * @irq_retrigger:	resend an IRQ to the CPU
  * @irq_set_type:	set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ
  * @irq_set_wake:	enable/disable power-management wake-on of an IRQ
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index aee8f7ec40af..638eb9c83d9f 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -95,8 +95,13 @@ static bool migrate_one_irq(struct irq_desc *desc)
 		affinity = cpu_online_mask;
 		brokeaff = true;
 	}
-
-	err = irq_do_set_affinity(d, affinity, true);
+	/*
+	 * Do not set the force argument of irq_do_set_affinity() as this
+	 * disables the masking of offline CPUs from the supplied affinity
+	 * mask and therefore might keep/reassign the irq to the outgoing
+	 * CPU.
+	 */
+	err = irq_do_set_affinity(d, affinity, false);
 	if (err) {
 		pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n",
 				    d->irq, err);

[GIT pull] irq fix for 4.13

[Thomas Gleixner]

Linus,

please pull the latest irq-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq-urgent-for-linus

Fix the fallout from reworking the locking and resource management in
request/free_irq().

Thanks,

	tglx

------------------>
Thomas Gleixner (1):
      genirq: Keep chip buslock across irq_request/release_resources()


 kernel/irq/manage.c | 63 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 53 insertions(+), 10 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 5624b2dd6b58..1d1a5b945ab4 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1090,6 +1090,16 @@ setup_irq_thread(struct irqaction *new, unsigned int irq, bool secondary)
 /*
  * Internal function to register an irqaction - typically used to
  * allocate special interrupts that are part of the architecture.
+ *
+ * Locking rules:
+ *
+ * desc->request_mutex	Provides serialization against a concurrent free_irq()
+ *   chip_bus_lock	Provides serialization for slow bus operations
+ *     desc->lock	Provides serialization against hard interrupts
+ *
+ * chip_bus_lock and desc->lock are sufficient for all other management and
+ * interrupt related functions. desc->request_mutex solely serializes
+ * request/free_irq().
  */
 static int
 __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
@@ -1167,20 +1177,35 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 	if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
 		new->flags &= ~IRQF_ONESHOT;
 
+	/*
+	 * Protects against a concurrent __free_irq() call which might wait
+	 * for synchronize_irq() to complete without holding the optional
+	 * chip bus lock and desc->lock.
+	 */
 	mutex_lock(&desc->request_mutex);
+
+	/*
+	 * Acquire bus lock as the irq_request_resources() callback below
+	 * might rely on the serialization or the magic power management
+	 * functions which are abusing the irq_bus_lock() callback,
+	 */
+	chip_bus_lock(desc);
+
+	/* First installed action requests resources. */
 	if (!desc->action) {
 		ret = irq_request_resources(desc);
 		if (ret) {
 			pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
 			       new->name, irq, desc->irq_data.chip->name);
-			goto out_mutex;
+			goto out_bus_unlock;
 		}
 	}
 
-	chip_bus_lock(desc);
-
 	/*
 	 * The following block of code has to be executed atomically
+	 * protected against a concurrent interrupt and any of the other
+	 * management calls which are not serialized via
+	 * desc->request_mutex or the optional bus lock.
 	 */
 	raw_spin_lock_irqsave(&desc->lock, flags);
 	old_ptr = &desc->action;
@@ -1286,10 +1311,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 			ret = __irq_set_trigger(desc,
 						new->flags & IRQF_TRIGGER_MASK);
 
-			if (ret) {
-				irq_release_resources(desc);
+			if (ret)
 				goto out_unlock;
-			}
 		}
 
 		desc->istate &= ~(IRQS_AUTODETECT | IRQS_SPURIOUS_DISABLED | \
@@ -1385,12 +1408,10 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 out_unlock:
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 
-	chip_bus_sync_unlock(desc);
-
 	if (!desc->action)
 		irq_release_resources(desc);
-
-out_mutex:
+out_bus_unlock:
+	chip_bus_sync_unlock(desc);
 	mutex_unlock(&desc->request_mutex);
 
 out_thread:
@@ -1472,6 +1493,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 			WARN(1, "Trying to free already-free IRQ %d\n", irq);
 			raw_spin_unlock_irqrestore(&desc->lock, flags);
 			chip_bus_sync_unlock(desc);
+			mutex_unlock(&desc->request_mutex);
 			return NULL;
 		}
 
@@ -1498,6 +1520,20 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 #endif
 
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
+	/*
+	 * Drop bus_lock here so the changes which were done in the chip
+	 * callbacks above are synced out to the irq chips which hang
+	 * behind a slow bus (I2C, SPI) before calling synchronize_irq().
+	 *
+	 * Aside of that the bus_lock can also be taken from the threaded
+	 * handler in irq_finalize_oneshot() which results in a deadlock
+	 * because synchronize_irq() would wait forever for the thread to
+	 * complete, which is blocked on the bus lock.
+	 *
+	 * The still held desc->request_mutex() protects against a
+	 * concurrent request_irq() of this irq so the release of resources
+	 * and timing data is properly serialized.
+	 */
 	chip_bus_sync_unlock(desc);
 
 	unregister_handler_proc(irq, action);
@@ -1530,8 +1566,15 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 		}
 	}
 
+	/* Last action releases resources */
 	if (!desc->action) {
+		/*
+		 * Reaquire bus lock as irq_release_resources() might
+		 * require it to deallocate resources over the slow bus.
+		 */
+		chip_bus_lock(desc);
 		irq_release_resources(desc);
+		chip_bus_sync_unlock(desc);
 		irq_remove_timings(desc);
 	}