4.4-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit cde4ad8368840e414ecf67db258fe1dabaa5fd2e ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hwtracing/stm/core.c | 17 +++++++++++++++++ drivers/hwtracing/stm/stm.h | 1 + 2 files changed, 18 insertions(+)
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index d4deac108578..f8e46c38b565 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -186,6 +186,9 @@ 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;
@@ -200,6 +203,9 @@ 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));
@@ -292,6 +298,7 @@ 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; @@ -308,6 +315,7 @@ 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; @@ -316,11 +324,18 @@ 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) { 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; @@ -343,6 +358,7 @@ 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)) @@ -953,6 +969,7 @@ 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; diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h index 97ee02241440..4e8c6926260f 100644 --- a/drivers/hwtracing/stm/stm.h +++ b/drivers/hwtracing/stm/stm.h @@ -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;