[PATCH v2 2/5] spi: Add lock context annotations for bus_lock_mutex

[Joseph CT Chan <jctchan@gmail.com>]

From: Bart Van Assche <bvanassche@acm.org>

Annotate spi_bus_lock() with __acquires(), spi_bus_unlock() with
__releases(), spi_sync_locked() and __spi_sync() with __must_hold(), and
spi_sync() with __must_not_hold() for bus_lock_mutex in
include/linux/spi/spi.h and drivers/spi/spi.c. Document exclusive SPI
bus lock ownership and enable static context analysis to verify locking
invariants across callers and the SPI core.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Joseph CT Chan <josephctchan@google.com>
---
 drivers/spi/spi.c       |  5 +++++
 include/linux/spi/spi.h | 12 ++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 85089b0ebf4b..01dfc25c1376 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -4959,6 +4959,7 @@ static void spi_complete(void *arg)
 }
 
 static int __spi_sync(struct spi_device *spi, struct spi_message *message)
+	__must_hold(&spi->controller->bus_lock_mutex)
 {
 	DECLARE_COMPLETION_ONSTACK(done);
 	unsigned long flags;
@@ -5045,6 +5046,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
  * Return: zero on success, else a negative error code.
  */
 int spi_sync(struct spi_device *spi, struct spi_message *message)
+	__must_not_hold(&spi->controller->bus_lock_mutex)
 {
 	int ret;
 
@@ -5073,6 +5075,7 @@ EXPORT_SYMBOL_GPL(spi_sync);
  * Return: zero on success, else a negative error code.
  */
 int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
+	__must_hold(&spi->controller->bus_lock_mutex)
 {
 	return __spi_sync(spi, message);
 }
@@ -5094,6 +5097,7 @@ EXPORT_SYMBOL_GPL(spi_sync_locked);
  * Return: always zero.
  */
 int spi_bus_lock(struct spi_controller *ctlr)
+	__acquires(&ctlr->bus_lock_mutex)
 {
 	unsigned long flags;
 
@@ -5123,6 +5127,7 @@ EXPORT_SYMBOL_GPL(spi_bus_lock);
  * Return: always zero.
  */
 int spi_bus_unlock(struct spi_controller *ctlr)
+	__releases(&ctlr->bus_lock_mutex)
 {
 	ctlr->bus_lock_flag = 0;
 
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index fb4baa0d3398..553c32987c97 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -1497,10 +1497,14 @@ extern int spi_split_transfers_maxwords(struct spi_controller *ctlr,
  * they will sleep uninterruptibly until the async transfer completes.
  */
 
-extern int spi_sync(struct spi_device *spi, struct spi_message *message);
-extern int spi_sync_locked(struct spi_device *spi, struct spi_message *message);
-extern int spi_bus_lock(struct spi_controller *ctlr);
-extern int spi_bus_unlock(struct spi_controller *ctlr);
+extern int spi_sync(struct spi_device *spi, struct spi_message *message)
+	__must_not_hold(&spi->controller->bus_lock_mutex);
+extern int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
+	__must_hold(&spi->controller->bus_lock_mutex);
+extern int spi_bus_lock(struct spi_controller *ctlr)
+	__acquires(&ctlr->bus_lock_mutex);
+extern int spi_bus_unlock(struct spi_controller *ctlr)
+	__releases(&ctlr->bus_lock_mutex);
 
 /**
  * spi_sync_transfer - synchronous SPI data transfer
-- 
2.56.0.385.gac671c819a-goog