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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>
This commit is contained in:
Alexander Shishkin 2016-02-15 19:12:06 +02:00 committed by Greg Kroah-Hartman
parent 1810f2c448
commit cde4ad8368
2 changed files with 18 additions and 0 deletions
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17
drivers/hwtracing/stm/core.c
View File

@ -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);
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 @@ stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
{
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 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width,
}
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 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width,
ret = 0;
unlock:
spin_unlock(&output->lock);
spin_unlock(&stm->mc_lock);
return ret;
@ -312,11 +320,18 @@ unlock:
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 @@ static int stm_char_open(struct inode *inode, struct file *file)
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 @@ int stm_source_register_device(struct device *parent,
if (err)
goto err;
stm_output_init(&src->output);
spin_lock_init(&src->link_lock);
INIT_LIST_HEAD(&src->link_entry);
src->data = data;

1
drivers/hwtracing/stm/stm.h
View File

@ -57,6 +57,7 @@ struct stm_device {
container_of((_d), struct stm_device, dev)
struct stm_output {
spinlock_t lock;
unsigned int master;
unsigned int channel;
unsigned int nr_chans;