From 6aa7de059173a986114ac43b8f50b297a86f09a8 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 23 Oct 2017 14:07:29 -0700 Subject: locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE() Please do not apply this to mainline directly, instead please re-run the coccinelle script shown below and apply its output. 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 harmful, and changing them results in churn. However, for some features, the read/write distinction is critical to correct operation. To distinguish these cases, separate read/write accessors must be used. This patch migrates (most) remaining ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following coccinelle script: ---- // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and // WRITE_ONCE() // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch 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: Linus Torvalds Cc: Peter Zijlstra 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/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- arch/arm/include/asm/spinlock.h | 2 +- arch/arm/mach-tegra/cpuidle-tegra20.c | 2 +- arch/arm/vdso/vgettimeofday.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index daa87212c9a1..77f50ae0aeb4 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -71,7 +71,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) while (lockval.tickets.next != lockval.tickets.owner) { wfe(); - lockval.tickets.owner = ACCESS_ONCE(lock->tickets.owner); + lockval.tickets.owner = READ_ONCE(lock->tickets.owner); } smp_mb(); diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c index 76e4c83cd5c8..3f24addd7972 100644 --- a/arch/arm/mach-tegra/cpuidle-tegra20.c +++ b/arch/arm/mach-tegra/cpuidle-tegra20.c @@ -179,7 +179,7 @@ static int tegra20_idle_lp2_coupled(struct cpuidle_device *dev, bool entered_lp2 = false; if (tegra_pending_sgi()) - ACCESS_ONCE(abort_flag) = true; + WRITE_ONCE(abort_flag, true); cpuidle_coupled_parallel_barrier(dev, &abort_barrier); diff --git a/arch/arm/vdso/vgettimeofday.c b/arch/arm/vdso/vgettimeofday.c index 79214d5ff097..a9dd619c6c29 100644 --- a/arch/arm/vdso/vgettimeofday.c +++ b/arch/arm/vdso/vgettimeofday.c @@ -35,7 +35,7 @@ static notrace u32 __vdso_read_begin(const struct vdso_data *vdata) { u32 seq; repeat: - seq = ACCESS_ONCE(vdata->seq_count); + seq = READ_ONCE(vdata->seq_count); if (seq & 1) { cpu_relax(); goto repeat; -- cgit v1.2.3