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Subject[PATCH 12/16] thunderbolt: Use spinlock in NHI serialization
Date
This is needed because ring polling functionality can be called from
atomic contexts when networking and other high-speed traffic is
transferred over a Thunderbolt cable.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Michael Jamet <michael.jamet@intel.com>
Reviewed-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
---
drivers/thunderbolt/nhi.c | 75 +++++++++++++++++++++++++--------------------
include/linux/thunderbolt.h | 2 +-
2 files changed, 42 insertions(+), 35 deletions(-)

diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index d1ad37c6eccf..cf1397afa72f 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -327,21 +327,9 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
if (transmit && hop == RING_E2E_UNUSED_HOPID)
return NULL;

- mutex_lock(&nhi->lock);
- if (hop >= nhi->hop_count) {
- dev_WARN(&nhi->pdev->dev, "invalid hop: %d\n", hop);
- goto err;
- }
- if (transmit && nhi->tx_rings[hop]) {
- dev_WARN(&nhi->pdev->dev, "TX hop %d already allocated\n", hop);
- goto err;
- } else if (!transmit && nhi->rx_rings[hop]) {
- dev_WARN(&nhi->pdev->dev, "RX hop %d already allocated\n", hop);
- goto err;
- }
ring = kzalloc(sizeof(*ring), GFP_KERNEL);
if (!ring)
- goto err;
+ return NULL;

spin_lock_init(&ring->lock);
INIT_LIST_HEAD(&ring->queue);
@@ -359,25 +347,45 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
ring->tail = 0;
ring->running = false;

- if (ring_request_msix(ring, flags & RING_FLAG_NO_SUSPEND))
- goto err;
-
ring->descriptors = dma_alloc_coherent(&ring->nhi->pdev->dev,
size * sizeof(*ring->descriptors),
&ring->descriptors_dma, GFP_KERNEL | __GFP_ZERO);
if (!ring->descriptors)
- goto err;
+ goto err_free_ring;

+ if (ring_request_msix(ring, flags & RING_FLAG_NO_SUSPEND))
+ goto err_free_descs;
+
+ spin_lock_irq(&nhi->lock);
+ if (hop >= nhi->hop_count) {
+ dev_WARN(&nhi->pdev->dev, "invalid hop: %d\n", hop);
+ goto err_release_msix;
+ }
+ if (transmit && nhi->tx_rings[hop]) {
+ dev_WARN(&nhi->pdev->dev, "TX hop %d already allocated\n", hop);
+ goto err_release_msix;
+ } else if (!transmit && nhi->rx_rings[hop]) {
+ dev_WARN(&nhi->pdev->dev, "RX hop %d already allocated\n", hop);
+ goto err_release_msix;
+ }
if (transmit)
nhi->tx_rings[hop] = ring;
else
nhi->rx_rings[hop] = ring;
- mutex_unlock(&nhi->lock);
+ spin_unlock_irq(&nhi->lock);
+
return ring;

-err:
+err_release_msix:
+ spin_unlock_irq(&nhi->lock);
+ ring_release_msix(ring);
+err_free_descs:
+ dma_free_coherent(&ring->nhi->pdev->dev,
+ ring->size * sizeof(*ring->descriptors),
+ ring->descriptors, ring->descriptors_dma);
+err_free_ring:
kfree(ring);
- mutex_unlock(&nhi->lock);
+
return NULL;
}

@@ -421,8 +429,8 @@ void tb_ring_start(struct tb_ring *ring)
u16 frame_size;
u32 flags;

- mutex_lock(&ring->nhi->lock);
- spin_lock_irq(&ring->lock);
+ spin_lock_irq(&ring->nhi->lock);
+ spin_lock(&ring->lock);
if (ring->nhi->going_away)
goto err;
if (ring->running) {
@@ -469,8 +477,8 @@ void tb_ring_start(struct tb_ring *ring)
ring_interrupt_active(ring, true);
ring->running = true;
err:
- spin_unlock_irq(&ring->lock);
- mutex_unlock(&ring->nhi->lock);
+ spin_unlock(&ring->lock);
+ spin_unlock_irq(&ring->nhi->lock);
}
EXPORT_SYMBOL_GPL(tb_ring_start);

@@ -489,8 +497,8 @@ EXPORT_SYMBOL_GPL(tb_ring_start);
*/
void tb_ring_stop(struct tb_ring *ring)
{
- mutex_lock(&ring->nhi->lock);
- spin_lock_irq(&ring->lock);
+ spin_lock_irq(&ring->nhi->lock);
+ spin_lock(&ring->lock);
dev_info(&ring->nhi->pdev->dev, "stopping %s %d\n",
RING_TYPE(ring), ring->hop);
if (ring->nhi->going_away)
@@ -511,8 +519,8 @@ void tb_ring_stop(struct tb_ring *ring)
ring->running = false;

err:
- spin_unlock_irq(&ring->lock);
- mutex_unlock(&ring->nhi->lock);
+ spin_unlock(&ring->lock);
+ spin_unlock_irq(&ring->nhi->lock);

/*
* schedule ring->work to invoke callbacks on all remaining frames.
@@ -534,7 +542,7 @@ EXPORT_SYMBOL_GPL(tb_ring_stop);
*/
void tb_ring_free(struct tb_ring *ring)
{
- mutex_lock(&ring->nhi->lock);
+ spin_lock_irq(&ring->nhi->lock);
/*
* Dissociate the ring from the NHI. This also ensures that
* nhi_interrupt_work cannot reschedule ring->work.
@@ -564,7 +572,7 @@ void tb_ring_free(struct tb_ring *ring)
RING_TYPE(ring),
ring->hop);

- mutex_unlock(&ring->nhi->lock);
+ spin_unlock_irq(&ring->nhi->lock);
/**
* ring->work can no longer be scheduled (it is scheduled only
* by nhi_interrupt_work, ring_stop and ring_msix). Wait for it
@@ -639,7 +647,7 @@ static void nhi_interrupt_work(struct work_struct *work)
int type = 0; /* current interrupt type 0: TX, 1: RX, 2: RX overflow */
struct tb_ring *ring;

- mutex_lock(&nhi->lock);
+ spin_lock_irq(&nhi->lock);

/*
* Starting at REG_RING_NOTIFY_BASE there are three status bitfields
@@ -677,7 +685,7 @@ static void nhi_interrupt_work(struct work_struct *work)
/* we do not check ring->running, this is done in ring->work */
schedule_work(&ring->work);
}
- mutex_unlock(&nhi->lock);
+ spin_unlock_irq(&nhi->lock);
}

static irqreturn_t nhi_msi(int irq, void *data)
@@ -766,7 +774,6 @@ static void nhi_shutdown(struct tb_nhi *nhi)
devm_free_irq(&nhi->pdev->dev, nhi->pdev->irq, nhi);
flush_work(&nhi->interrupt_work);
}
- mutex_destroy(&nhi->lock);
ida_destroy(&nhi->msix_ida);
}

@@ -855,7 +862,7 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
return res;
}

- mutex_init(&nhi->lock);
+ spin_lock_init(&nhi->lock);

pci_set_master(pdev);

diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index 51af0a5fa52f..62adb97d77f1 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -415,7 +415,7 @@ static inline struct tb_xdomain *tb_service_parent(struct tb_service *svc)
* @hop_count: Number of rings (end point hops) supported by NHI.
*/
struct tb_nhi {
- struct mutex lock;
+ spinlock_t lock;
struct pci_dev *pdev;
void __iomem *iobase;
struct tb_ring **tx_rings;
--
2.13.5
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