[PATCH v2] dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue

[Rex Zhang <rex.zhang@intel.com>]

The drain_workqueue() is not in a locked context. In the multi-task case,
it's possible to call queue_work() when drain_workqueue() is ongoing, then
it can cause Call Trace due to pushing a work into a draining workqueue:
    Call Trace:
    <TASK>
    ? __warn+0x7d/0x140
    ? __queue_work+0x2b2/0x440
    ? report_bug+0x1f8/0x200
    ? handle_bug+0x3c/0x70
    ? exc_invalid_op+0x18/0x70
    ? asm_exc_invalid_op+0x1a/0x20
    ? __queue_work+0x2b2/0x440
    queue_work_on+0x28/0x30
    idxd_misc_thread+0x303/0x5a0 [idxd]
    ? __schedule+0x369/0xb40
    ? __pfx_irq_thread_fn+0x10/0x10
    ? irq_thread+0xbc/0x1b0
    irq_thread_fn+0x21/0x70
    irq_thread+0x102/0x1b0
    ? preempt_count_add+0x74/0xa0
    ? __pfx_irq_thread_dtor+0x10/0x10
    ? __pfx_irq_thread+0x10/0x10
    kthread+0x103/0x140
    ? __pfx_kthread+0x10/0x10
    ret_from_fork+0x31/0x50
    ? __pfx_kthread+0x10/0x10
    ret_from_fork_asm+0x1b/0x30
    </TASK>
The original lock for event log was spinlock, drain_workqueue() can't
be in a spinlocked context because it may cause task rescheduling. The
spinlock was called in thread and irq thread context, the current usages
does not require a spinlock for event log, so it's feasible to convert
spinlock to mutex.
For putting drain_workqueue() into a locked context, convert the spinlock
to mutex, then lock drain_workqueue() by mutex.

Fixes: c40bd7d9737b ("dmaengine: idxd: process user page faults for completion record")
Signed-off-by: Rex Zhang <rex.zhang@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Lijun Pan <lijun.pan@intel.com>
---
Changelog:
v2:
- Update commit message.
---
 drivers/dma/idxd/cdev.c    | 5 ++---
 drivers/dma/idxd/debugfs.c | 4 ++--
 drivers/dma/idxd/device.c  | 8 ++++----
 drivers/dma/idxd/idxd.h    | 2 +-
 drivers/dma/idxd/init.c    | 2 +-
 drivers/dma/idxd/irq.c     | 4 ++--
 6 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index 0423655f5a88..556cac187612 100644
--- a/drivers/dma/idxd/cdev.c
+++ b/drivers/dma/idxd/cdev.c
@@ -342,7 +342,7 @@ static void idxd_cdev_evl_drain_pasid(struct idxd_wq *wq, u32 pasid)
 	if (!evl)
 		return;
 
-	spin_lock(&evl->lock);
+	mutex_lock(&evl->lock);
 	status.bits = ioread64(idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
 	t = status.tail;
 	h = evl->head;
@@ -354,9 +354,8 @@ static void idxd_cdev_evl_drain_pasid(struct idxd_wq *wq, u32 pasid)
 			set_bit(h, evl->bmap);
 		h = (h + 1) % size;
 	}
-	spin_unlock(&evl->lock);
-
 	drain_workqueue(wq->wq);
+	mutex_unlock(&evl->lock);
 }
 
 static int idxd_cdev_release(struct inode *node, struct file *filep)
diff --git a/drivers/dma/idxd/debugfs.c b/drivers/dma/idxd/debugfs.c
index 9cfbd9b14c4c..7f689b3aff65 100644
--- a/drivers/dma/idxd/debugfs.c
+++ b/drivers/dma/idxd/debugfs.c
@@ -66,7 +66,7 @@ static int debugfs_evl_show(struct seq_file *s, void *d)
 	if (!evl || !evl->log)
 		return 0;
 
-	spin_lock(&evl->lock);
+	mutex_lock(&evl->lock);
 
 	h = evl->head;
 	evl_status.bits = ioread64(idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
@@ -87,7 +87,7 @@ static int debugfs_evl_show(struct seq_file *s, void *d)
 		dump_event_entry(idxd, s, i, &count, processed);
 	}
 
-	spin_unlock(&evl->lock);
+	mutex_unlock(&evl->lock);
 	return 0;
 }
 
diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 8f754f922217..042e076a6f2a 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -770,7 +770,7 @@ static int idxd_device_evl_setup(struct idxd_device *idxd)
 		goto err_alloc;
 	}
 
-	spin_lock(&evl->lock);
+	mutex_lock(&evl->lock);
 	evl->log = addr;
 	evl->dma = dma_addr;
 	evl->log_size = size;
@@ -791,7 +791,7 @@ static int idxd_device_evl_setup(struct idxd_device *idxd)
 	gencfg.evl_en = 1;
 	iowrite32(gencfg.bits, idxd->reg_base + IDXD_GENCFG_OFFSET);
 
-	spin_unlock(&evl->lock);
+	mutex_unlock(&evl->lock);
 	return 0;
 
 err_alloc:
@@ -811,7 +811,7 @@ static void idxd_device_evl_free(struct idxd_device *idxd)
 	if (!gencfg.evl_en)
 		return;
 
-	spin_lock(&evl->lock);
+	mutex_lock(&evl->lock);
 	gencfg.evl_en = 0;
 	iowrite32(gencfg.bits, idxd->reg_base + IDXD_GENCFG_OFFSET);
 
@@ -826,7 +826,7 @@ static void idxd_device_evl_free(struct idxd_device *idxd)
 	bitmap_free(evl->bmap);
 	evl->log = NULL;
 	evl->size = IDXD_EVL_SIZE_MIN;
-	spin_unlock(&evl->lock);
+	mutex_unlock(&evl->lock);
 }
 
 static void idxd_group_config_write(struct idxd_group *group)
diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
index 1e89c80a07fc..b925c972b99b 100644
--- a/drivers/dma/idxd/idxd.h
+++ b/drivers/dma/idxd/idxd.h
@@ -283,7 +283,7 @@ struct idxd_driver_data {
 
 struct idxd_evl {
 	/* Lock to protect event log access. */
-	spinlock_t lock;
+	struct mutex lock;
 	void *log;
 	dma_addr_t dma;
 	/* Total size of event log = number of entries * entry size. */
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 0eb1c827a215..611101f99405 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -351,7 +351,7 @@ static int idxd_init_evl(struct idxd_device *idxd)
 	if (!evl)
 		return -ENOMEM;
 
-	spin_lock_init(&evl->lock);
+	mutex_init(&evl->lock);
 	evl->size = IDXD_EVL_SIZE_MIN;
 
 	idxd->evl_cache = kmem_cache_create(dev_name(idxd_confdev(idxd)),
diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
index 2183d7f9cdbd..3037eda986de 100644
--- a/drivers/dma/idxd/irq.c
+++ b/drivers/dma/idxd/irq.c
@@ -363,7 +363,7 @@ static void process_evl_entries(struct idxd_device *idxd)
 	evl_status.bits = 0;
 	evl_status.int_pending = 1;
 
-	spin_lock(&evl->lock);
+	mutex_lock(&evl->lock);
 	/* Clear interrupt pending bit */
 	iowrite32(evl_status.bits_upper32,
 		  idxd->reg_base + IDXD_EVLSTATUS_OFFSET + sizeof(u32));
@@ -381,7 +381,7 @@ static void process_evl_entries(struct idxd_device *idxd)
 	evl->head = h;
 	evl_status.head = h;
 	iowrite32(evl_status.bits_lower32, idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
-	spin_unlock(&evl->lock);
+	mutex_unlock(&evl->lock);
 }
 
 irqreturn_t idxd_misc_thread(int vec, void *data)
-- 
2.25.1