stm class: Guard output assignment against concurrency
It is possible to concurrently assign the same output (a character
device writer or an stm_source device) to different stm devices,
which sets off a strategically placed warning in stm_output_assign().
To avoid this, use a spinlock to serialize (un)assignments between
outputs and stm devices.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 4a626d8..f6ade21 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -185,6 +185,9 @@
{
struct stp_master *master = stm_master(stm, output->master);
+ lockdep_assert_held(&stm->mc_lock);
+ lockdep_assert_held(&output->lock);
+
if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
return;
@@ -199,6 +202,9 @@
{
struct stp_master *master = stm_master(stm, output->master);
+ lockdep_assert_held(&stm->mc_lock);
+ lockdep_assert_held(&output->lock);
+
bitmap_release_region(&master->chan_map[0], output->channel,
ilog2(output->nr_chans));
@@ -288,6 +294,7 @@
}
spin_lock(&stm->mc_lock);
+ spin_lock(&output->lock);
/* output is already assigned -- shouldn't happen */
if (WARN_ON_ONCE(output->nr_chans))
goto unlock;
@@ -304,6 +311,7 @@
ret = 0;
unlock:
+ spin_unlock(&output->lock);
spin_unlock(&stm->mc_lock);
return ret;
@@ -312,11 +320,18 @@
static void stm_output_free(struct stm_device *stm, struct stm_output *output)
{
spin_lock(&stm->mc_lock);
+ spin_lock(&output->lock);
if (output->nr_chans)
stm_output_disclaim(stm, output);
+ spin_unlock(&output->lock);
spin_unlock(&stm->mc_lock);
}
+static void stm_output_init(struct stm_output *output)
+{
+ spin_lock_init(&output->lock);
+}
+
static int major_match(struct device *dev, const void *data)
{
unsigned int major = *(unsigned int *)data;
@@ -339,6 +354,7 @@
if (!stmf)
return -ENOMEM;
+ stm_output_init(&stmf->output);
stmf->stm = to_stm_device(dev);
if (!try_module_get(stmf->stm->owner))
@@ -952,6 +968,7 @@
if (err)
goto err;
+ stm_output_init(&src->output);
spin_lock_init(&src->link_lock);
INIT_LIST_HEAD(&src->link_entry);
src->data = data;