[PATCH 0/3] Fixed some issues and cleanup of ultrasoc-smb

[PATCH 0/3] Fixed some issues and cleanup of ultrasoc-smb

[Junhao He]

Fix the two issues listed below and code cleanup
a) Fixed the BUG of atomic-sleep
b) Fixed uninitialized before use buf_hw_base

Junhao He (3):
  coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb
  coresight: ultrasoc-smb: simplify the code for check to_copy valid
  coresight: ultrasoc-smb: fix uninitialized before use buf_hw_base

 drivers/hwtracing/coresight/ultrasoc-smb.c | 49 +++++++++-------------
 drivers/hwtracing/coresight/ultrasoc-smb.h |  6 +--
 2 files changed, 23 insertions(+), 32 deletions(-)

-- 
2.33.0

[PATCH 1/3] coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb

[Junhao He]

When we to enable the SMB by perf, the perf sched will call perf_ctx_lock()
to close system preempt in event_function_call(). But SMB::enable_smb() use
mutex to lock the critical section, which may sleep.

 BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 153023, name: perf
 preempt_count: 2, expected: 0
 RCU nest depth: 0, expected: 0
 INFO: lockdep is turned off.
 irq event stamp: 0
 hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 hardirqs last disabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
 softirqs last  enabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
 softirqs last disabled at (0): [<0000000000000000>] 0x0
 CPU: 2 PID: 153023 Comm: perf Kdump: loaded Tainted: G   W  O   6.5.0-rc4+ #1

 Call trace:
 ...
  __mutex_lock+0xbc/0xa70
  mutex_lock_nested+0x34/0x48
  smb_update_buffer+0x58/0x360 [ultrasoc_smb]
  etm_event_stop+0x204/0x2d8 [coresight]
  etm_event_del+0x1c/0x30 [coresight]
  event_sched_out+0x17c/0x3b8
  group_sched_out.part.0+0x5c/0x208
  __perf_event_disable+0x15c/0x210
  event_function+0xe0/0x230
  remote_function+0xb4/0xe8
  generic_exec_single+0x160/0x268
  smp_call_function_single+0x20c/0x2a0
  event_function_call+0x20c/0x220
  _perf_event_disable+0x5c/0x90
  perf_event_for_each_child+0x58/0xc0
  _perf_ioctl+0x34c/0x1250
  perf_ioctl+0x64/0x98
...

Use spinlock replace mutex to control driver data access to one at a
time. But the function copy_to_user() may sleep so spinlock do not to
lock it.

Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 36 ++++++++++------------
 drivers/hwtracing/coresight/ultrasoc-smb.h |  6 ++--
 2 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index e9a32a97fbee..b08a619d1116 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -99,7 +99,7 @@ static int smb_open(struct inode *inode, struct file *file)
 					struct smb_drv_data, miscdev);
 	int ret = 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	if (drvdata->reading) {
 		ret = -EBUSY;
@@ -115,7 +115,7 @@ static int smb_open(struct inode *inode, struct file *file)
 
 	drvdata->reading = true;
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
 	if (!len)
 		return 0;
 
-	mutex_lock(&drvdata->mutex);
-
 	if (!sdb->data_size)
-		goto out;
+		return 0;
 
 	to_copy = min(sdb->data_size, len);
 
@@ -145,20 +143,18 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
 
 	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
 		dev_dbg(dev, "Failed to copy data to user\n");
-		to_copy = -EFAULT;
-		goto out;
+		return -EFAULT;
 	}
 
+	spin_lock(&drvdata->spinlock);
 	*ppos += to_copy;
-
 	smb_update_read_ptr(drvdata, to_copy);
 
-	dev_dbg(dev, "%zu bytes copied\n", to_copy);
-out:
 	if (!sdb->data_size)
 		smb_reset_buffer(drvdata);
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
+	dev_dbg(dev, "%zu bytes copied\n", to_copy);
 	return to_copy;
 }
 
@@ -167,9 +163,9 @@ static int smb_release(struct inode *inode, struct file *file)
 	struct smb_drv_data *drvdata = container_of(file->private_data,
 					struct smb_drv_data, miscdev);
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 	drvdata->reading = false;
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return 0;
 }
@@ -262,7 +258,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	int ret = 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	/* Do nothing, the trace data is reading by other interface now */
 	if (drvdata->reading) {
@@ -294,7 +290,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 
 	dev_dbg(&csdev->dev, "Ultrasoc SMB enabled\n");
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -304,7 +300,7 @@ static int smb_disable(struct coresight_device *csdev)
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	int ret = 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	if (drvdata->reading) {
 		ret = -EBUSY;
@@ -327,7 +323,7 @@ static int smb_disable(struct coresight_device *csdev)
 
 	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled\n");
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -408,7 +404,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
 	if (!buf)
 		return 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	/* Don't do anything if another tracer is using this sink. */
 	if (atomic_read(&csdev->refcnt) != 1)
@@ -432,7 +428,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
 	if (!buf->snapshot && lost)
 		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return data_size;
 }
@@ -590,7 +586,7 @@ static int smb_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	mutex_init(&drvdata->mutex);
+	spin_lock_init(&drvdata->spinlock);
 	drvdata->pid = -1;
 
 	ret = smb_register_sink(pdev, drvdata);
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
index d2e14e8d2c8a..82a44c14a882 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.h
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
@@ -8,7 +8,7 @@
 #define _ULTRASOC_SMB_H
 
 #include <linux/miscdevice.h>
-#include <linux/mutex.h>
+#include <linux/spinlock.h>
 
 /* Offset of SMB global registers */
 #define SMB_GLB_CFG_REG		0x00
@@ -105,7 +105,7 @@ struct smb_data_buffer {
  * @csdev:	Component vitals needed by the framework.
  * @sdb:	Data buffer for SMB.
  * @miscdev:	Specifics to handle "/dev/xyz.smb" entry.
- * @mutex:	Control data access to one at a time.
+ * @spinlock:	Control data access to one at a time.
  * @reading:	Synchronise user space access to SMB buffer.
  * @pid:	Process ID of the process being monitored by the
  *		session that is using this component.
@@ -116,7 +116,7 @@ struct smb_drv_data {
 	struct coresight_device	*csdev;
 	struct smb_data_buffer sdb;
 	struct miscdevice miscdev;
-	struct mutex mutex;
+	spinlock_t spinlock;
 	bool reading;
 	pid_t pid;
 	enum cs_mode mode;
-- 
2.33.0

[PATCH 2/3] coresight: ultrasoc-smb: simplify the code for check to_copy valid

[Junhao He]

We only need to check once when before using the to_copy variable
to simplify the code.

Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index b08a619d1116..e78edc3480ce 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -127,20 +127,15 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
 					struct smb_drv_data, miscdev);
 	struct smb_data_buffer *sdb = &drvdata->sdb;
 	struct device *dev = &drvdata->csdev->dev;
-	ssize_t to_copy = 0;
-
-	if (!len)
-		return 0;
-
-	if (!sdb->data_size)
-		return 0;
-
-	to_copy = min(sdb->data_size, len);
+	ssize_t to_copy = min(sdb->data_size, len);
 
 	/* Copy parts of trace data when read pointer wrap around SMB buffer */
 	if (sdb->buf_rdptr + to_copy > sdb->buf_size)
 		to_copy = sdb->buf_size - sdb->buf_rdptr;
 
+	if (!to_copy)
+		return 0;
+
 	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
 		dev_dbg(dev, "Failed to copy data to user\n");
 		return -EFAULT;
-- 
2.33.0

[PATCH 3/3] coresight: ultrasoc-smb: fix uninitialized before use buf_hw_base

[Junhao He]

In smb_reset_buffer, the sdb->buf_hw_base variable is uninitialized
before use, which initializes it in smb_init_data_buffer. And the SMB
regiester are set in smb_config_inport.
So move the call after smb_config_inport.

Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")

Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index e78edc3480ce..21ba473786e5 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -475,7 +475,6 @@ static int smb_init_data_buffer(struct platform_device *pdev,
 static void smb_init_hw(struct smb_drv_data *drvdata)
 {
 	smb_disable_hw(drvdata);
-	smb_reset_buffer(drvdata);
 
 	writel(SMB_LB_CFG_LO_DEFAULT, drvdata->base + SMB_LB_CFG_LO_REG);
 	writel(SMB_LB_CFG_HI_DEFAULT, drvdata->base + SMB_LB_CFG_HI_REG);
@@ -597,6 +596,7 @@ static int smb_probe(struct platform_device *pdev)
 	}
 
 	platform_set_drvdata(pdev, drvdata);
+	smb_reset_buffer(drvdata);
 
 	return 0;
 }
-- 
2.33.0

Re: [PATCH 3/3] coresight: ultrasoc-smb: fix uninitialized before use buf_hw_base

[Yicong Yang]

On 2023/10/12 17:47, Junhao He wrote:
> In smb_reset_buffer, the sdb->buf_hw_base variable is uninitialized
> before use, which initializes it in smb_init_data_buffer. And the SMB
> regiester are set in smb_config_inport.
> So move the call after smb_config_inport.
> 
> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
> 
> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> ---
>  drivers/hwtracing/coresight/ultrasoc-smb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
> index e78edc3480ce..21ba473786e5 100644
> --- a/drivers/hwtracing/coresight/ultrasoc-smb.c
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
> @@ -475,7 +475,6 @@ static int smb_init_data_buffer(struct platform_device *pdev,
>  static void smb_init_hw(struct smb_drv_data *drvdata)
>  {
>  	smb_disable_hw(drvdata);
> -	smb_reset_buffer(drvdata);
>  
>  	writel(SMB_LB_CFG_LO_DEFAULT, drvdata->base + SMB_LB_CFG_LO_REG);
>  	writel(SMB_LB_CFG_HI_DEFAULT, drvdata->base + SMB_LB_CFG_HI_REG);
> @@ -597,6 +596,7 @@ static int smb_probe(struct platform_device *pdev)
>  	}
>  
>  	platform_set_drvdata(pdev, drvdata);
> +	smb_reset_buffer(drvdata);

Shouldn't we reset the buffer before registering the sink? Otherwise it'll
be possible for user to access an unreset one.

>  
>  	return 0;
>  }
> 

Re: [PATCH 1/3] coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb

[Yicong Yang]

On 2023/10/12 17:47, Junhao He wrote:
> When we to enable the SMB by perf, the perf sched will call perf_ctx_lock()
> to close system preempt in event_function_call(). But SMB::enable_smb() use
> mutex to lock the critical section, which may sleep.
> 
>  BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
>  in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 153023, name: perf
>  preempt_count: 2, expected: 0
>  RCU nest depth: 0, expected: 0
>  INFO: lockdep is turned off.
>  irq event stamp: 0
>  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>  hardirqs last disabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
>  softirqs last  enabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
>  softirqs last disabled at (0): [<0000000000000000>] 0x0
>  CPU: 2 PID: 153023 Comm: perf Kdump: loaded Tainted: G   W  O   6.5.0-rc4+ #1
> 
>  Call trace:
>  ...
>   __mutex_lock+0xbc/0xa70
>   mutex_lock_nested+0x34/0x48
>   smb_update_buffer+0x58/0x360 [ultrasoc_smb]
>   etm_event_stop+0x204/0x2d8 [coresight]
>   etm_event_del+0x1c/0x30 [coresight]
>   event_sched_out+0x17c/0x3b8
>   group_sched_out.part.0+0x5c/0x208
>   __perf_event_disable+0x15c/0x210
>   event_function+0xe0/0x230
>   remote_function+0xb4/0xe8
>   generic_exec_single+0x160/0x268
>   smp_call_function_single+0x20c/0x2a0
>   event_function_call+0x20c/0x220
>   _perf_event_disable+0x5c/0x90
>   perf_event_for_each_child+0x58/0xc0
>   _perf_ioctl+0x34c/0x1250
>   perf_ioctl+0x64/0x98
> ...
> 
> Use spinlock replace mutex to control driver data access to one at a
> time. But the function copy_to_user() may sleep so spinlock do not to
> lock it.
> 
> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> ---
>  drivers/hwtracing/coresight/ultrasoc-smb.c | 36 ++++++++++------------
>  drivers/hwtracing/coresight/ultrasoc-smb.h |  6 ++--
>  2 files changed, 19 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
> index e9a32a97fbee..b08a619d1116 100644
> --- a/drivers/hwtracing/coresight/ultrasoc-smb.c
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
> @@ -99,7 +99,7 @@ static int smb_open(struct inode *inode, struct file *file)
>  					struct smb_drv_data, miscdev);
>  	int ret = 0;
>  
> -	mutex_lock(&drvdata->mutex);
> +	spin_lock(&drvdata->spinlock);
>  
>  	if (drvdata->reading) {
>  		ret = -EBUSY;
> @@ -115,7 +115,7 @@ static int smb_open(struct inode *inode, struct file *file)
>  
>  	drvdata->reading = true;
>  out:
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>  
>  	return ret;
>  }
> @@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>  	if (!len)
>  		return 0;
>  
> -	mutex_lock(&drvdata->mutex);
> -
>  	if (!sdb->data_size)
> -		goto out;
> +		return 0;
>  
>  	to_copy = min(sdb->data_size, len);
>  
> @@ -145,20 +143,18 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>  
>  	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
>  		dev_dbg(dev, "Failed to copy data to user\n");
> -		to_copy = -EFAULT;
> -		goto out;
> +		return -EFAULT;
>  	}
>  
> +	spin_lock(&drvdata->spinlock);
>  	*ppos += to_copy;
> -
>  	smb_update_read_ptr(drvdata, to_copy);
>  
> -	dev_dbg(dev, "%zu bytes copied\n", to_copy);
> -out:
>  	if (!sdb->data_size)
>  		smb_reset_buffer(drvdata);
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);

Do we still need the lock here? If we get here, we should have the exclusive
access to the file, which is protected in open(). Or any other cases?

>  
> +	dev_dbg(dev, "%zu bytes copied\n", to_copy);
>  	return to_copy;
>  }
>  
> @@ -167,9 +163,9 @@ static int smb_release(struct inode *inode, struct file *file)
>  	struct smb_drv_data *drvdata = container_of(file->private_data,
>  					struct smb_drv_data, miscdev);
>  
> -	mutex_lock(&drvdata->mutex);
> +	spin_lock(&drvdata->spinlock);
>  	drvdata->reading = false;
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>  
>  	return 0;
>  }
> @@ -262,7 +258,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
>  	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
>  	int ret = 0;
>  
> -	mutex_lock(&drvdata->mutex);
> +	spin_lock(&drvdata->spinlock);
>  
>  	/* Do nothing, the trace data is reading by other interface now */
>  	if (drvdata->reading) {
> @@ -294,7 +290,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
>  
>  	dev_dbg(&csdev->dev, "Ultrasoc SMB enabled\n");
>  out:
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>  
>  	return ret;
>  }
> @@ -304,7 +300,7 @@ static int smb_disable(struct coresight_device *csdev)
>  	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
>  	int ret = 0;
>  
> -	mutex_lock(&drvdata->mutex);
> +	spin_lock(&drvdata->spinlock);
>  
>  	if (drvdata->reading) {
>  		ret = -EBUSY;
> @@ -327,7 +323,7 @@ static int smb_disable(struct coresight_device *csdev)
>  
>  	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled\n");
>  out:
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>  
>  	return ret;
>  }
> @@ -408,7 +404,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
>  	if (!buf)
>  		return 0;
>  
> -	mutex_lock(&drvdata->mutex);
> +	spin_lock(&drvdata->spinlock);
>  
>  	/* Don't do anything if another tracer is using this sink. */
>  	if (atomic_read(&csdev->refcnt) != 1)
> @@ -432,7 +428,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
>  	if (!buf->snapshot && lost)
>  		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
>  out:
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>  
>  	return data_size;
>  }
> @@ -590,7 +586,7 @@ static int smb_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	mutex_init(&drvdata->mutex);
> +	spin_lock_init(&drvdata->spinlock);
>  	drvdata->pid = -1;
>  
>  	ret = smb_register_sink(pdev, drvdata);
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
> index d2e14e8d2c8a..82a44c14a882 100644
> --- a/drivers/hwtracing/coresight/ultrasoc-smb.h
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
> @@ -8,7 +8,7 @@
>  #define _ULTRASOC_SMB_H
>  
>  #include <linux/miscdevice.h>
> -#include <linux/mutex.h>
> +#include <linux/spinlock.h>
>  
>  /* Offset of SMB global registers */
>  #define SMB_GLB_CFG_REG		0x00
> @@ -105,7 +105,7 @@ struct smb_data_buffer {
>   * @csdev:	Component vitals needed by the framework.
>   * @sdb:	Data buffer for SMB.
>   * @miscdev:	Specifics to handle "/dev/xyz.smb" entry.
> - * @mutex:	Control data access to one at a time.
> + * @spinlock:	Control data access to one at a time.
>   * @reading:	Synchronise user space access to SMB buffer.
>   * @pid:	Process ID of the process being monitored by the
>   *		session that is using this component.
> @@ -116,7 +116,7 @@ struct smb_drv_data {
>  	struct coresight_device	*csdev;
>  	struct smb_data_buffer sdb;
>  	struct miscdevice miscdev;
> -	struct mutex mutex;
> +	spinlock_t spinlock;
>  	bool reading;
>  	pid_t pid;
>  	enum cs_mode mode;
> 

Re: [PATCH 1/3] coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb

[hejunhao]

Hi Yicong,


On 2023/10/19 11:05, Yicong Yang wrote:
> On 2023/10/12 17:47, Junhao He wrote:
>
>
> Use spinlock replace mutex to control driver data access to one at a
> time. But the function copy_to_user() may sleep so spinlock do not to
> lock it.
>
> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> ---
>   drivers/hwtracing/coresight/ultrasoc-smb.c | 36 ++++++++++------------
>   drivers/hwtracing/coresight/ultrasoc-smb.h |  6 ++--
>   2 files changed, 19 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
> index e9a32a97fbee..b08a619d1116 100644
> --- a/drivers/hwtracing/coresight/ultrasoc-smb.c
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
> @@ -99,7 +99,7 @@ static int smb_open(struct inode *inode, struct file *file)
>   					struct smb_drv_data, miscdev);
>   	int ret = 0;
>   
> -	mutex_lock(&drvdata->mutex);
> +	spin_lock(&drvdata->spinlock);
>   
>   	if (drvdata->reading) {
>   		ret = -EBUSY;
> @@ -115,7 +115,7 @@ static int smb_open(struct inode *inode, struct file *file)
>   
>   	drvdata->reading = true;
>   out:
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>   
>   	return ret;
>   }
> @@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>   	if (!len)
>   		return 0;
>   
> -	mutex_lock(&drvdata->mutex);
> -
>   	if (!sdb->data_size)
> -		goto out;
> +		return 0;
>   
>   	to_copy = min(sdb->data_size, len);
>   
> @@ -145,20 +143,18 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>   
>   	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
>   		dev_dbg(dev, "Failed to copy data to user\n");
> -		to_copy = -EFAULT;
> -		goto out;
> +		return -EFAULT;
>   	}
>   
> +	spin_lock(&drvdata->spinlock);
>   	*ppos += to_copy;
> -
>   	smb_update_read_ptr(drvdata, to_copy);
>   
> -	dev_dbg(dev, "%zu bytes copied\n", to_copy);
> -out:
>   	if (!sdb->data_size)
>   		smb_reset_buffer(drvdata);
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
> Do we still need the lock here? If we get here, we should have the exclusive
> access to the file, which is protected in open(). Or any other cases?

This is something I've also considered. If someone opens an SMB device
and reads it using multithreading, The SMB device will got out of sync.
I've seen other coresight sink drivers such as etb do not use locks in
the read function.
Maybe it's not necessary here, the buffer synchronization
is guaranteed by the user.

Best regards,
Junhao.

Re: [PATCH 3/3] coresight: ultrasoc-smb: fix uninitialized before use buf_hw_base

[hejunhao]

On 2023/10/19 10:34, Yicong Yang wrote:
> On 2023/10/12 17:47, Junhao He wrote:
>> In smb_reset_buffer, the sdb->buf_hw_base variable is uninitialized
>> before use, which initializes it in smb_init_data_buffer. And the SMB
>> regiester are set in smb_config_inport.
>> So move the call after smb_config_inport.
>>
>> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
>>
>> Signed-off-by: Junhao He <hejunhao3@huawei.com>
>> ---
>>   drivers/hwtracing/coresight/ultrasoc-smb.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
>> index e78edc3480ce..21ba473786e5 100644
>> --- a/drivers/hwtracing/coresight/ultrasoc-smb.c
>> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
>> @@ -475,7 +475,6 @@ static int smb_init_data_buffer(struct platform_device *pdev,
>>   static void smb_init_hw(struct smb_drv_data *drvdata)
>>   {
>>   	smb_disable_hw(drvdata);
>> -	smb_reset_buffer(drvdata);
>>   
>>   	writel(SMB_LB_CFG_LO_DEFAULT, drvdata->base + SMB_LB_CFG_LO_REG);
>>   	writel(SMB_LB_CFG_HI_DEFAULT, drvdata->base + SMB_LB_CFG_HI_REG);
>> @@ -597,6 +596,7 @@ static int smb_probe(struct platform_device *pdev)
>>   	}
>>   
>>   	platform_set_drvdata(pdev, drvdata);
>> +	smb_reset_buffer(drvdata);
> Shouldn't we reset the buffer before registering the sink? Otherwise it'll
> be possible for user to access an unreset one.
>

Hi Yicong,

Thanks for the comments!

The code after the smb_register_sink() function also needs to moved.
I will fix all in next version.

Best regards,
Junhao.

Re: [PATCH 1/3] coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb

[Jonathan Cameron]

On Thu, 12 Oct 2023 17:47:04 +0800
Junhao He <hejunhao3@huawei.com> wrote:

> When we to enable the SMB by perf, the perf sched will call perf_ctx_lock()
> to close system preempt in event_function_call(). But SMB::enable_smb() use
> mutex to lock the critical section, which may sleep.
> 
>  BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
>  in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 153023, name: perf
>  preempt_count: 2, expected: 0
>  RCU nest depth: 0, expected: 0
>  INFO: lockdep is turned off.
>  irq event stamp: 0
>  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>  hardirqs last disabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
>  softirqs last  enabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
>  softirqs last disabled at (0): [<0000000000000000>] 0x0
>  CPU: 2 PID: 153023 Comm: perf Kdump: loaded Tainted: G   W  O   6.5.0-rc4+ #1
> 
>  Call trace:
>  ...
>   __mutex_lock+0xbc/0xa70
>   mutex_lock_nested+0x34/0x48
>   smb_update_buffer+0x58/0x360 [ultrasoc_smb]
>   etm_event_stop+0x204/0x2d8 [coresight]
>   etm_event_del+0x1c/0x30 [coresight]
>   event_sched_out+0x17c/0x3b8
>   group_sched_out.part.0+0x5c/0x208
>   __perf_event_disable+0x15c/0x210
>   event_function+0xe0/0x230
>   remote_function+0xb4/0xe8
>   generic_exec_single+0x160/0x268
>   smp_call_function_single+0x20c/0x2a0
>   event_function_call+0x20c/0x220
>   _perf_event_disable+0x5c/0x90
>   perf_event_for_each_child+0x58/0xc0
>   _perf_ioctl+0x34c/0x1250
>   perf_ioctl+0x64/0x98
> ...
> 
> Use spinlock replace mutex to control driver data access to one at a
> time. But the function copy_to_user() may sleep so spinlock do not to
> lock it.

I'd like to see a comment on why we no longer need to lock over the copy_to_user
rather than simply that we can't.

> 
> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
> Signed-off-by: Junhao He <hejunhao3@huawei.com>

A follow up patch could change a lot of this to use the new cleanup.h (don't want that
in the fix though as will make back porting trickier.).
That should let you do
guard(spin_lock)(&drvdata->spinlock);
and then use direct returns instead of goto complexity.



Jonathan

> @@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>  	if (!len)
>  		return 0;
>  
> -	mutex_lock(&drvdata->mutex);
> -
>  	if (!sdb->data_size)
> -		goto out;
> +		return 0;
>  
>  	to_copy = min(sdb->data_size, len);
>  
> @@ -145,20 +143,18 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>  
>  	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
>  		dev_dbg(dev, "Failed to copy data to user\n");
> -		to_copy = -EFAULT;
> -		goto out;
> +		return -EFAULT;
>  	}
>  
> +	spin_lock(&drvdata->spinlock);
>  	*ppos += to_copy;
> -

Unrelated white space change that shouldn't be here.

>  	smb_update_read_ptr(drvdata, to_copy);
>  
> -	dev_dbg(dev, "%zu bytes copied\n", to_copy);
> -out:
>  	if (!sdb->data_size)
>  		smb_reset_buffer(drvdata);
> -	mutex_unlock(&drvdata->mutex);
> +	spin_unlock(&drvdata->spinlock);
>  
> +	dev_dbg(dev, "%zu bytes copied\n", to_copy);
>  	return to_copy;
>  }

Re: [PATCH 2/3] coresight: ultrasoc-smb: simplify the code for check to_copy valid

[Jonathan Cameron]

On Thu, 12 Oct 2023 17:47:05 +0800
Junhao He <hejunhao3@huawei.com> wrote:

> We only need to check once when before using the to_copy variable
> to simplify the code.
> 
> Signed-off-by: Junhao He <hejunhao3@huawei.com>

I'm not convinced this one is an improvement. Sometimes it's easier to just
see the individual conditions checked even if we could combine them.
It's easy to understand we don't copy data if:
a) We ask for 0 data.
b) There is 0 data

Less easy to establish that with the extra wrap around code in there
(even though that has no impact on to_copy if it is 0)

Jonathan


> ---
>  drivers/hwtracing/coresight/ultrasoc-smb.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
> index b08a619d1116..e78edc3480ce 100644
> --- a/drivers/hwtracing/coresight/ultrasoc-smb.c
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
> @@ -127,20 +127,15 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>  					struct smb_drv_data, miscdev);
>  	struct smb_data_buffer *sdb = &drvdata->sdb;
>  	struct device *dev = &drvdata->csdev->dev;
> -	ssize_t to_copy = 0;
> -
> -	if (!len)
> -		return 0;
> -
> -	if (!sdb->data_size)
> -		return 0;
> -
> -	to_copy = min(sdb->data_size, len);
> +	ssize_t to_copy = min(sdb->data_size, len);
>  
>  	/* Copy parts of trace data when read pointer wrap around SMB buffer */
>  	if (sdb->buf_rdptr + to_copy > sdb->buf_size)
>  		to_copy = sdb->buf_size - sdb->buf_rdptr;
>  
> +	if (!to_copy)
> +		return 0;
> +
>  	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
>  		dev_dbg(dev, "Failed to copy data to user\n");
>  		return -EFAULT;

Re: [PATCH 2/3] coresight: ultrasoc-smb: simplify the code for check to_copy valid

[hejunhao]

On 2023/10/19 21:35, Jonathan Cameron wrote:
> On Thu, 12 Oct 2023 17:47:05 +0800
> Junhao He <hejunhao3@huawei.com> wrote:
>
>> We only need to check once when before using the to_copy variable
>> to simplify the code.
>>
>> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> I'm not convinced this one is an improvement. Sometimes it's easier to just
> see the individual conditions checked even if we could combine them.
> It's easy to understand we don't copy data if:
> a) We ask for 0 data.
> b) There is 0 data
>
> Less easy to establish that with the extra wrap around code in there
> (even though that has no impact on to_copy if it is 0)
>
> Jonathan
>

Thanks, I will drop this patch.

Best regards,
Junhao.

>> ---
>>   drivers/hwtracing/coresight/ultrasoc-smb.c | 13 ++++---------
>>   1 file changed, 4 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
>> index b08a619d1116..e78edc3480ce 100644
>> --- a/drivers/hwtracing/coresight/ultrasoc-smb.c
>> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
>> @@ -127,20 +127,15 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>>   					struct smb_drv_data, miscdev);
>>   	struct smb_data_buffer *sdb = &drvdata->sdb;
>>   	struct device *dev = &drvdata->csdev->dev;
>> -	ssize_t to_copy = 0;
>> -
>> -	if (!len)
>> -		return 0;
>> -
>> -	if (!sdb->data_size)
>> -		return 0;
>> -
>> -	to_copy = min(sdb->data_size, len);
>> +	ssize_t to_copy = min(sdb->data_size, len);
>>   
>>   	/* Copy parts of trace data when read pointer wrap around SMB buffer */
>>   	if (sdb->buf_rdptr + to_copy > sdb->buf_size)
>>   		to_copy = sdb->buf_size - sdb->buf_rdptr;
>>   
>> +	if (!to_copy)
>> +		return 0;
>> +
>>   	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
>>   		dev_dbg(dev, "Failed to copy data to user\n");
>>   		return -EFAULT;
> .
>

Re: [PATCH 1/3] coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb

[hejunhao]

Hi Jonathan,


On 2023/10/19 21:30, Jonathan Cameron wrote:
> On Thu, 12 Oct 2023 17:47:04 +0800
> Junhao He <hejunhao3@huawei.com> wrote:
>
>> When we to enable the SMB by perf, the perf sched will call perf_ctx_lock()
>> to close system preempt in event_function_call(). But SMB::enable_smb() use
>> mutex to lock the critical section, which may sleep.
>>
>>   BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
>>   in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 153023, name: perf
>>   preempt_count: 2, expected: 0
>>   RCU nest depth: 0, expected: 0
>>   INFO: lockdep is turned off.
>>   irq event stamp: 0
>>   hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>>   hardirqs last disabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
>>   softirqs last  enabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
>>   softirqs last disabled at (0): [<0000000000000000>] 0x0
>>   CPU: 2 PID: 153023 Comm: perf Kdump: loaded Tainted: G   W  O   6.5.0-rc4+ #1
>>
>>   Call trace:
>>   ...
>>    __mutex_lock+0xbc/0xa70
>>    mutex_lock_nested+0x34/0x48
>>    smb_update_buffer+0x58/0x360 [ultrasoc_smb]
>>    etm_event_stop+0x204/0x2d8 [coresight]
>>    etm_event_del+0x1c/0x30 [coresight]
>>    event_sched_out+0x17c/0x3b8
>>    group_sched_out.part.0+0x5c/0x208
>>    __perf_event_disable+0x15c/0x210
>>    event_function+0xe0/0x230
>>    remote_function+0xb4/0xe8
>>    generic_exec_single+0x160/0x268
>>    smp_call_function_single+0x20c/0x2a0
>>    event_function_call+0x20c/0x220
>>    _perf_event_disable+0x5c/0x90
>>    perf_event_for_each_child+0x58/0xc0
>>    _perf_ioctl+0x34c/0x1250
>>    perf_ioctl+0x64/0x98
>> ...
>>
>> Use spinlock replace mutex to control driver data access to one at a
>> time. But the function copy_to_user() may sleep so spinlock do not to
>> lock it.
> I'd like to see a comment on why we no longer need to lock over the copy_to_user
> rather than simply that we can't.

Yes, I will do that.

>> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
>> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> A follow up patch could change a lot of this to use the new cleanup.h (don't want that
> in the fix though as will make back porting trickier.).
> That should let you do
> guard(spin_lock)(&drvdata->spinlock);
> and then use direct returns instead of goto complexity.
>
>
>
> Jonathan

Thanks for sharing.
I will append up a new patch to use guards to reduce gotos.

>
>> @@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>>   	if (!len)
>>   		return 0;
>>   
>> -	mutex_lock(&drvdata->mutex);
>> -
>>   	if (!sdb->data_size)
>> -		goto out;
>> +		return 0;
>>   
>>   	to_copy = min(sdb->data_size, len);
>>   
>> @@ -145,20 +143,18 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
>>   
>>   	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
>>   		dev_dbg(dev, "Failed to copy data to user\n");
>> -		to_copy = -EFAULT;
>> -		goto out;
>> +		return -EFAULT;
>>   	}
>>   
>> +	spin_lock(&drvdata->spinlock);
>>   	*ppos += to_copy;
>> -
> Unrelated white space change that shouldn't be here.

Ok, i will drop this white space



Thanks for the comments!

Best regards,
Junhao.

>
>>   	smb_update_read_ptr(drvdata, to_copy);
>>   
>> -	dev_dbg(dev, "%zu bytes copied\n", to_copy);
>> -out:
>>   	if (!sdb->data_size)
>>   		smb_reset_buffer(drvdata);
>> -	mutex_unlock(&drvdata->mutex);
>> +	spin_unlock(&drvdata->spinlock);
>>   
>> +	dev_dbg(dev, "%zu bytes copied\n", to_copy);
>>   	return to_copy;
>>   }
>
> .
>