[PATCH v2 1/4] coresight: ultrasoc-smb: Fix sleep while close preempt in enable_smb
Junhao He
hejunhao3 at huawei.com
Sat Oct 21 01:38:19 PDT 2023
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 to replace mutex to control driver data access to one at a
time. The function copy_to_user() may sleep, it cannot be in a spinlock
context, so we can't simply replace it in smb_read(). But we can ensure
that only one user gets the SMB device fd by smb_open(), so remove the
locks from smb_read() and buffer synchronization is guaranteed by the user.
Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
Signed-off-by: Junhao He <hejunhao3 at huawei.com>
---
drivers/hwtracing/coresight/ultrasoc-smb.c | 35 +++++++++-------------
drivers/hwtracing/coresight/ultrasoc-smb.h | 6 ++--
2 files changed, 17 insertions(+), 24 deletions(-)
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index e9a32a97fbee..0a0fe9fcc57f 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 +143,15 @@ 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;
}
*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);
+ dev_dbg(dev, "%zu bytes copied\n", to_copy);
return to_copy;
}
@@ -167,9 +160,9 @@ 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 +255,7 @@ 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 +287,7 @@ 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 +297,7 @@ 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 +320,7 @@ 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 +401,7 @@ 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 +425,7 @@ 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 +583,7 @@ 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
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