[PATCH 11/16] thunderbolt: Use spinlock in ring serialization

[Mika Westerberg]

This makes it possible to enqueue frames also from atomic context which
is needed for example, when networking packets are sent over a
Thunderbolt cable.

Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
Reviewed-by: Michael Jamet <michael.ja...@intel.com>
Reviewed-by: Yehezkel Bernat <yehezkel.ber...@intel.com>
---
 drivers/thunderbolt/nhi.c   | 26 ++++++++++++++------------
 include/linux/thunderbolt.h |  2 +-
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index 4704ccd20c84..d1ad37c6eccf 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -212,8 +212,10 @@ static void ring_work(struct work_struct *work)
        struct tb_ring *ring = container_of(work, typeof(*ring), work);
        struct ring_frame *frame;
        bool canceled = false;
+       unsigned long flags;
        LIST_HEAD(done);
-       mutex_lock(&ring->lock);
+
+       spin_lock_irqsave(&ring->lock, flags);
 
        if (!ring->running) {
                /*  Move all frames to done and mark them as canceled. */
@@ -241,7 +243,8 @@ static void ring_work(struct work_struct *work)
        ring_write_descriptors(ring);
 
 invoke_callback:
-       mutex_unlock(&ring->lock); /* allow callbacks to schedule new work */
+       /* allow callbacks to schedule new work */
+       spin_unlock_irqrestore(&ring->lock, flags);
        while (!list_empty(&done)) {
                frame = list_first_entry(&done, typeof(*frame), list);
                /*
@@ -255,15 +258,17 @@ static void ring_work(struct work_struct *work)
 
 int __tb_ring_enqueue(struct tb_ring *ring, struct ring_frame *frame)
 {
+       unsigned long flags;
        int ret = 0;
-       mutex_lock(&ring->lock);
+
+       spin_lock_irqsave(&ring->lock, flags);
        if (ring->running) {
                list_add_tail(&frame->list, &ring->queue);
                ring_write_descriptors(ring);
        } else {
                ret = -ESHUTDOWN;
        }
-       mutex_unlock(&ring->lock);
+       spin_unlock_irqrestore(&ring->lock, flags);
        return ret;
 }
 EXPORT_SYMBOL_GPL(__tb_ring_enqueue);
@@ -338,7 +343,7 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, 
u32 hop, int size,
        if (!ring)
                goto err;
 
-       mutex_init(&ring->lock);
+       spin_lock_init(&ring->lock);
        INIT_LIST_HEAD(&ring->queue);
        INIT_LIST_HEAD(&ring->in_flight);
        INIT_WORK(&ring->work, ring_work);
@@ -371,8 +376,6 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, 
u32 hop, int size,
        return ring;
 
 err:
-       if (ring)
-               mutex_destroy(&ring->lock);
        kfree(ring);
        mutex_unlock(&nhi->lock);
        return NULL;
@@ -419,7 +422,7 @@ void tb_ring_start(struct tb_ring *ring)
        u32 flags;
 
        mutex_lock(&ring->nhi->lock);
-       mutex_lock(&ring->lock);
+       spin_lock_irq(&ring->lock);
        if (ring->nhi->going_away)
                goto err;
        if (ring->running) {
@@ -466,7 +469,7 @@ void tb_ring_start(struct tb_ring *ring)
        ring_interrupt_active(ring, true);
        ring->running = true;
 err:
-       mutex_unlock(&ring->lock);
+       spin_unlock_irq(&ring->lock);
        mutex_unlock(&ring->nhi->lock);
 }
 EXPORT_SYMBOL_GPL(tb_ring_start);
@@ -487,7 +490,7 @@ EXPORT_SYMBOL_GPL(tb_ring_start);
 void tb_ring_stop(struct tb_ring *ring)
 {
        mutex_lock(&ring->nhi->lock);
-       mutex_lock(&ring->lock);
+       spin_lock_irq(&ring->lock);
        dev_info(&ring->nhi->pdev->dev, "stopping %s %d\n",
                 RING_TYPE(ring), ring->hop);
        if (ring->nhi->going_away)
@@ -508,7 +511,7 @@ void tb_ring_stop(struct tb_ring *ring)
        ring->running = false;
 
 err:
-       mutex_unlock(&ring->lock);
+       spin_unlock_irq(&ring->lock);
        mutex_unlock(&ring->nhi->lock);
 
        /*
@@ -568,7 +571,6 @@ void tb_ring_free(struct tb_ring *ring)
         * to finish before freeing the ring.
         */
        flush_work(&ring->work);
-       mutex_destroy(&ring->lock);
        kfree(ring);
 }
 EXPORT_SYMBOL_GPL(tb_ring_free);
diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index fac4ff62c0de..51af0a5fa52f 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -448,7 +448,7 @@ struct tb_nhi {
  * @eof_mask: Bit mask used to detect end of frame PDF
  */
 struct tb_ring {
-       struct mutex lock;
+       spinlock_t lock;
        struct tb_nhi *nhi;
        int size;
        int hop;
-- 
2.13.5