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 <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
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/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

9 files changed, 12 insertions, 12 deletions

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 03505ffbe1b6..eaa0ba66cf96 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -75,7 +75,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
 	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
 		BUG_ON(regs != task_pt_regs(current));
 
-	work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
+	work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
 
 	if (unlikely(work & _TIF_SYSCALL_EMU))
 		emulated = true;
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index fa8dbfcf7ed3..11b13c4b43d5 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -318,7 +318,7 @@ int gettimeofday(struct timeval *, struct timezone *)
 notrace time_t __vdso_time(time_t *t)
 {
 	/* This is atomic on x86 so we don't need any locks. */
-	time_t result = ACCESS_ONCE(gtod->wall_time_sec);
+	time_t result = READ_ONCE(gtod->wall_time_sec);
 
 	if (t)
 		*t = result;
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 589af1eec7c1..140d33288e78 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2118,7 +2118,7 @@ static int x86_pmu_event_init(struct perf_event *event)
 			event->destroy(event);
 	}
 
-	if (ACCESS_ONCE(x86_pmu.attr_rdpmc))
+	if (READ_ONCE(x86_pmu.attr_rdpmc))
 		event->hw.flags |= PERF_X86_EVENT_RDPMC_ALLOWED;
 
 	return err;
diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 022e59714562..53dd162576a8 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -48,7 +48,7 @@ static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
 	unsigned ret;
 
 repeat:
-	ret = ACCESS_ONCE(s->seq);
+	ret = READ_ONCE(s->seq);
 	if (unlikely(ret & 1)) {
 		cpu_relax();
 		goto repeat;
diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
index 9c4e7ba6870c..7d7715dde901 100644
--- a/arch/x86/kernel/espfix_64.c
+++ b/arch/x86/kernel/espfix_64.c
@@ -155,14 +155,14 @@ void init_espfix_ap(int cpu)
 	page = cpu/ESPFIX_STACKS_PER_PAGE;
 
 	/* Did another CPU already set this up? */
-	stack_page = ACCESS_ONCE(espfix_pages[page]);
+	stack_page = READ_ONCE(espfix_pages[page]);
 	if (likely(stack_page))
 		goto done;
 
 	mutex_lock(&espfix_init_mutex);
 
 	/* Did we race on the lock? */
-	stack_page = ACCESS_ONCE(espfix_pages[page]);
+	stack_page = READ_ONCE(espfix_pages[page]);
 	if (stack_page)
 		goto unlock_done;
 
@@ -200,7 +200,7 @@ void init_espfix_ap(int cpu)
 		set_pte(&pte_p[n*PTE_STRIDE], pte);
 
 	/* Job is done for this CPU and any CPU which shares this page */
-	ACCESS_ONCE(espfix_pages[page]) = stack_page;
+	WRITE_ONCE(espfix_pages[page], stack_page);
 
 unlock_done:
 	mutex_unlock(&espfix_init_mutex);
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 35aafc95e4b8..18bc9b51ac9b 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -105,7 +105,7 @@ static void nmi_max_handler(struct irq_work *w)
 {
 	struct nmiaction *a = container_of(w, struct nmiaction, irq_work);
 	int remainder_ns, decimal_msecs;
-	u64 whole_msecs = ACCESS_ONCE(a->max_duration);
+	u64 whole_msecs = READ_ONCE(a->max_duration);
 
 	remainder_ns = do_div(whole_msecs, (1000 * 1000));
 	decimal_msecs = remainder_ns / 1000;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 7a69cf053711..a119b361b8b7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -443,7 +443,7 @@ static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
 
 static u64 __get_spte_lockless(u64 *sptep)
 {
-	return ACCESS_ONCE(*sptep);
+	return READ_ONCE(*sptep);
 }
 #else
 union split_spte {
@@ -4819,7 +4819,7 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 	 * If we don't have indirect shadow pages, it means no page is
 	 * write-protected, so we can exit simply.
 	 */
-	if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
+	if (!READ_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
 		return;
 
 	remote_flush = local_flush = false;
diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
index ea67dc876316..01c1371f39f8 100644
--- a/arch/x86/kvm/page_track.c
+++ b/arch/x86/kvm/page_track.c
@@ -157,7 +157,7 @@ bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,
 		return false;
 
 	index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL);
-	return !!ACCESS_ONCE(slot->arch.gfn_track[mode][index]);
+	return !!READ_ONCE(slot->arch.gfn_track[mode][index]);
 }
 
 void kvm_page_track_cleanup(struct kvm *kvm)
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 6083ba462f35..13b4f19b9131 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -547,7 +547,7 @@ int xen_alloc_p2m_entry(unsigned long pfn)
 	if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
 		topidx = p2m_top_index(pfn);
 		top_mfn_p = &p2m_top_mfn[topidx];
-		mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
+		mid_mfn = READ_ONCE(p2m_top_mfn_p[topidx]);
 
 		BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);