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locking/atomics, firmware/ivc: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()

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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@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-3-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mark Rutland 2017-10-23 14:07:13 -07:00 committed by Ingo Molnar
parent 332efa6374
commit eeafcc5a59
1 changed files with 12 additions and 12 deletions
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24
drivers/firmware/tegra/ivc.c
View File

@ -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);