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-rw-r--r--drivers/hwtracing/intel_th/msu.c92
1 files changed, 49 insertions, 43 deletions
diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index 25af214..ee15306 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -122,7 +122,6 @@ struct msc {
atomic_t mmap_count;
struct mutex buf_mutex;
- struct mutex iter_mutex;
struct list_head iter_list;
/* config */
@@ -257,23 +256,37 @@ static struct msc_iter *msc_iter_install(struct msc *msc)
iter = kzalloc(sizeof(*iter), GFP_KERNEL);
if (!iter)
- return NULL;
+ return ERR_PTR(-ENOMEM);
+
+ mutex_lock(&msc->buf_mutex);
+
+ /*
+ * Reading and tracing are mutually exclusive; if msc is
+ * enabled, open() will fail; otherwise existing readers
+ * will prevent enabling the msc and the rest of fops don't
+ * need to worry about it.
+ */
+ if (msc->enabled) {
+ kfree(iter);
+ iter = ERR_PTR(-EBUSY);
+ goto unlock;
+ }
msc_iter_init(iter);
iter->msc = msc;
- mutex_lock(&msc->iter_mutex);
list_add_tail(&iter->entry, &msc->iter_list);
- mutex_unlock(&msc->iter_mutex);
+unlock:
+ mutex_unlock(&msc->buf_mutex);
return iter;
}
static void msc_iter_remove(struct msc_iter *iter, struct msc *msc)
{
- mutex_lock(&msc->iter_mutex);
+ mutex_lock(&msc->buf_mutex);
list_del(&iter->entry);
- mutex_unlock(&msc->iter_mutex);
+ mutex_unlock(&msc->buf_mutex);
kfree(iter);
}
@@ -454,7 +467,6 @@ static void msc_buffer_clear_hw_header(struct msc *msc)
{
struct msc_window *win;
- mutex_lock(&msc->buf_mutex);
list_for_each_entry(win, &msc->win_list, entry) {
unsigned int blk;
size_t hw_sz = sizeof(struct msc_block_desc) -
@@ -466,7 +478,6 @@ static void msc_buffer_clear_hw_header(struct msc *msc)
memset(&bdesc->hw_tag, 0, hw_sz);
}
}
- mutex_unlock(&msc->buf_mutex);
}
/**
@@ -474,12 +485,15 @@ static void msc_buffer_clear_hw_header(struct msc *msc)
* @msc: the MSC device to configure
*
* Program storage mode, wrapping, burst length and trace buffer address
- * into a given MSC. If msc::enabled is set, enable the trace, too.
+ * into a given MSC. Then, enable tracing and set msc::enabled.
+ * The latter is serialized on msc::buf_mutex, so make sure to hold it.
*/
static int msc_configure(struct msc *msc)
{
u32 reg;
+ lockdep_assert_held(&msc->buf_mutex);
+
if (msc->mode > MSC_MODE_MULTI)
return -ENOTSUPP;
@@ -497,21 +511,19 @@ static int msc_configure(struct msc *msc)
reg = ioread32(msc->reg_base + REG_MSU_MSC0CTL);
reg &= ~(MSC_MODE | MSC_WRAPEN | MSC_EN | MSC_RD_HDR_OVRD);
+ reg |= MSC_EN;
reg |= msc->mode << __ffs(MSC_MODE);
reg |= msc->burst_len << __ffs(MSC_LEN);
- /*if (msc->mode == MSC_MODE_MULTI)
- reg |= MSC_RD_HDR_OVRD; */
+
if (msc->wrap)
reg |= MSC_WRAPEN;
- if (msc->enabled)
- reg |= MSC_EN;
iowrite32(reg, msc->reg_base + REG_MSU_MSC0CTL);
- if (msc->enabled) {
- msc->thdev->output.multiblock = msc->mode == MSC_MODE_MULTI;
- intel_th_trace_enable(msc->thdev);
- }
+ msc->thdev->output.multiblock = msc->mode == MSC_MODE_MULTI;
+ intel_th_trace_enable(msc->thdev);
+ msc->enabled = 1;
+
return 0;
}
@@ -521,15 +533,14 @@ static int msc_configure(struct msc *msc)
* @msc: MSC device to disable
*
* If @msc is enabled, disable tracing on the switch and then disable MSC
- * storage.
+ * storage. Caller must hold msc::buf_mutex.
*/
static void msc_disable(struct msc *msc)
{
unsigned long count;
u32 reg;
- if (!msc->enabled)
- return;
+ lockdep_assert_held(&msc->buf_mutex);
intel_th_trace_disable(msc->thdev);
@@ -569,33 +580,35 @@ static void msc_disable(struct msc *msc)
static int intel_th_msc_activate(struct intel_th_device *thdev)
{
struct msc *msc = dev_get_drvdata(&thdev->dev);
- int ret = 0;
+ int ret = -EBUSY;
if (!atomic_inc_unless_negative(&msc->user_count))
return -ENODEV;
- mutex_lock(&msc->iter_mutex);
- if (!list_empty(&msc->iter_list))
- ret = -EBUSY;
- mutex_unlock(&msc->iter_mutex);
+ mutex_lock(&msc->buf_mutex);
- if (ret) {
- atomic_dec(&msc->user_count);
- return ret;
- }
+ /* if there are readers, refuse */
+ if (list_empty(&msc->iter_list))
+ ret = msc_configure(msc);
- msc->enabled = 1;
+ mutex_unlock(&msc->buf_mutex);
+
+ if (ret)
+ atomic_dec(&msc->user_count);
- return msc_configure(msc);
+ return ret;
}
static void intel_th_msc_deactivate(struct intel_th_device *thdev)
{
struct msc *msc = dev_get_drvdata(&thdev->dev);
- msc_disable(msc);
-
- atomic_dec(&msc->user_count);
+ mutex_lock(&msc->buf_mutex);
+ if (msc->enabled) {
+ msc_disable(msc);
+ atomic_dec(&msc->user_count);
+ }
+ mutex_unlock(&msc->buf_mutex);
}
/**
@@ -1035,8 +1048,8 @@ static int intel_th_msc_open(struct inode *inode, struct file *file)
return -EPERM;
iter = msc_iter_install(msc);
- if (!iter)
- return -ENOMEM;
+ if (IS_ERR(iter))
+ return PTR_ERR(iter);
file->private_data = iter;
@@ -1101,11 +1114,6 @@ static ssize_t intel_th_msc_read(struct file *file, char __user *buf,
if (!atomic_inc_unless_negative(&msc->user_count))
return 0;
- if (msc->enabled) {
- ret = -EBUSY;
- goto put_count;
- }
-
if (msc->mode == MSC_MODE_SINGLE && !msc->single_wrap)
size = msc->single_sz;
else
@@ -1254,8 +1262,6 @@ static int intel_th_msc_init(struct msc *msc)
msc->mode = MSC_MODE_MULTI;
mutex_init(&msc->buf_mutex);
INIT_LIST_HEAD(&msc->win_list);
-
- mutex_init(&msc->iter_mutex);
INIT_LIST_HEAD(&msc->iter_list);
msc->burst_len =
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