From eeafcc5a5925d0819dad462eac1d42fda5fbe36f Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 23 Oct 2017 14:07:13 -0700 Subject: [PATCH] locking/atomics, firmware/ivc: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() 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 Signed-off-by: Paul E. McKenney Cc: Jonathan Hunter Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thierry Reding Cc: Thomas Gleixner 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 --- 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); -- GitLab