On 14/11/2023 13:33, 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 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@huawei.com
Reviewed-by: James Clark james.clark@arm.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;