From: Mark Rutland <mark.rutland@xxxxxxx>
workqueue: kill off ACCESS_ONCE()
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.
However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.
It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts the Tegra IVC code and comments to use
{READ,WRITE}_ONCE() consistently.
----
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Jonathan Hunter <jonathanh@xxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
---
drivers/firmware/tegra/ivc.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/drivers/firmware/tegra/ivc.c b/drivers/firmware/tegra/ivc.c
index a01461d63f68..00de793e6423 100644
--- a/drivers/firmware/tegra/ivc.c
+++ b/drivers/firmware/tegra/ivc.c
@@ -99,11 +99,11 @@ static inline bool tegra_ivc_empty(struct tegra_ivc *ivc,
{
/*
* This function performs multiple checks on the same values with
- * security implications, so create snapshots with ACCESS_ONCE() to
+ * security implications, so create snapshots with READ_ONCE() to
* ensure that these checks use the same values.
*/
- u32 tx = ACCESS_ONCE(header->tx.count);
- u32 rx = ACCESS_ONCE(header->rx.count);
+ u32 tx = READ_ONCE(header->tx.count);
+ u32 rx = READ_ONCE(header->rx.count);
/*
* Perform an over-full check to prevent denial of service attacks
@@ -124,8 +124,8 @@ static inline bool tegra_ivc_empty(struct tegra_ivc *ivc,
static inline bool tegra_ivc_full(struct tegra_ivc *ivc,
struct tegra_ivc_header *header)
{
- u32 tx = ACCESS_ONCE(header->tx.count);
- u32 rx = ACCESS_ONCE(header->rx.count);
+ u32 tx = READ_ONCE(header->tx.count);
+ u32 rx = READ_ONCE(header->rx.count);
/*
* Invalid cases where the counters indicate that the queue is over
@@ -137,8 +137,8 @@ static inline bool tegra_ivc_full(struct tegra_ivc *ivc,
static inline u32 tegra_ivc_available(struct tegra_ivc *ivc,
struct tegra_ivc_header *header)
{
- u32 tx = ACCESS_ONCE(header->tx.count);
- u32 rx = ACCESS_ONCE(header->rx.count);
+ u32 tx = READ_ONCE(header->tx.count);
+ u32 rx = READ_ONCE(header->rx.count);
/*
* This function isn't expected to be used in scenarios where an
@@ -151,8 +151,8 @@ static inline u32 tegra_ivc_available(struct tegra_ivc *ivc,
static inline void tegra_ivc_advance_tx(struct tegra_ivc *ivc)
{
- ACCESS_ONCE(ivc->tx.channel->tx.count) =
- ACCESS_ONCE(ivc->tx.channel->tx.count) + 1;
+ WRITE_ONCE(ivc->tx.channel->tx.count,
+ READ_ONCE(ivc->tx.channel->tx.count) + 1);
if (ivc->tx.position == ivc->num_frames - 1)
ivc->tx.position = 0;
@@ -162,8 +162,8 @@ static inline void tegra_ivc_advance_tx(struct tegra_ivc *ivc)
static inline void tegra_ivc_advance_rx(struct tegra_ivc *ivc)
{
- ACCESS_ONCE(ivc->rx.channel->rx.count) =
- ACCESS_ONCE(ivc->rx.channel->rx.count) + 1;
+ WRITE_ONCE(ivc->rx.channel->rx.count,
+ READ_ONCE(ivc->rx.channel->rx.count) + 1);
if (ivc->rx.position == ivc->num_frames - 1)
ivc->rx.position = 0;
@@ -428,7 +428,7 @@ int tegra_ivc_notified(struct tegra_ivc *ivc)
/* Copy the receiver's state out of shared memory. */
tegra_ivc_invalidate(ivc, ivc->rx.phys + offset);
- state = ACCESS_ONCE(ivc->rx.channel->tx.state);
+ state = READ_ONCE(ivc->rx.channel->tx.state);
if (state == TEGRA_IVC_STATE_SYNC) {
offset = offsetof(struct tegra_ivc_header, tx.count);
--
2.5.2
