Commit cde4ad83 authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Greg Kroah-Hartman
Browse files

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: default avatarAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1810f2c4

drivers/hwtracing/stm/core.c

+17 −0
Original line number Original line Diff line number Diff line
@@ -185,6 +185,9 @@ static void stm_output_claim(struct stm_device *stm, struct stm_output *output) 
{

{

	struct stp_master *master = stm_master(stm, output->master);

	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))

	if (WARN_ON_ONCE(master->nr_free < output->nr_chans))

		return;

		return;
@@ -199,6 +202,9 @@ stm_output_disclaim(struct stm_device *stm, struct stm_output *output) 
{

{

	struct stp_master *master = stm_master(stm, output->master);

	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,

	bitmap_release_region(&master->chan_map[0], output->channel,

			      ilog2(output->nr_chans));

			      ilog2(output->nr_chans));
@@ -288,6 +294,7 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width, 
	}

	}





	spin_lock(&stm->mc_lock);

	spin_lock(&stm->mc_lock);

	spin_lock(&output->lock);

	/* output is already assigned -- shouldn't happen */

	/* output is already assigned -- shouldn't happen */

	if (WARN_ON_ONCE(output->nr_chans))

	if (WARN_ON_ONCE(output->nr_chans))

		goto unlock;

		goto unlock;
@@ -304,6 +311,7 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width, 




	ret = 0;

	ret = 0;

unlock:

unlock:

	spin_unlock(&output->lock);

	spin_unlock(&stm->mc_lock);

	spin_unlock(&stm->mc_lock);





	return ret;

	return ret;
@@ -312,11 +320,18 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width, 
static void stm_output_free(struct stm_device *stm, struct stm_output *output)

static void stm_output_free(struct stm_device *stm, struct stm_output *output)

{

{

	spin_lock(&stm->mc_lock);

	spin_lock(&stm->mc_lock);

	spin_lock(&output->lock);

	if (output->nr_chans)

	if (output->nr_chans)

		stm_output_disclaim(stm, output);

		stm_output_disclaim(stm, output);

	spin_unlock(&output->lock);

	spin_unlock(&stm->mc_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)

static int major_match(struct device *dev, const void *data)

{

{

	unsigned int major = *(unsigned int *)data;

	unsigned int major = *(unsigned int *)data;
@@ -339,6 +354,7 @@ static int stm_char_open(struct inode *inode, struct file *file) 
	if (!stmf)

	if (!stmf)

		return -ENOMEM;

		return -ENOMEM;





	stm_output_init(&stmf->output);

	stmf->stm = to_stm_device(dev);

	stmf->stm = to_stm_device(dev);





	if (!try_module_get(stmf->stm->owner))

	if (!try_module_get(stmf->stm->owner))
@@ -952,6 +968,7 @@ int stm_source_register_device(struct device *parent, 
	if (err)

	if (err)

		goto err;

		goto err;





	stm_output_init(&src->output);

	spin_lock_init(&src->link_lock);

	spin_lock_init(&src->link_lock);

	INIT_LIST_HEAD(&src->link_entry);

	INIT_LIST_HEAD(&src->link_entry);

	src->data = data;

	src->data = data;

drivers/hwtracing/stm/stm.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -57,6 +57,7 @@ struct stm_device { 
	container_of((_d), struct stm_device, dev)

	container_of((_d), struct stm_device, dev)





struct stm_output {

struct stm_output {

	spinlock_t		lock;

	unsigned int		master;

	unsigned int		master;

	unsigned int		channel;

	unsigned int		channel;

	unsigned int		nr_chans;

	unsigned int		nr_chans;