Commit 6aa7de05 authored by Mark Rutland's avatar Mark Rutland Committed by Ingo Molnar
Browse files

locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns... 


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: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarPaul 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: default avatarIngo Molnar <mingo@kernel.org>
parent b03a0fe0

arch/arc/kernel/smp.c

+1 −1
Original line number Diff line number Diff line
@@ -245,7 +245,7 @@ static void ipi_send_msg_one(int cpu, enum ipi_msg_type msg) 
	 * and read back old value

	 */

	do {

		new = old = ACCESS_ONCE(*ipi_data_ptr);

		new = old = READ_ONCE(*ipi_data_ptr);

		new |= 1U << msg;

	} while (cmpxchg(ipi_data_ptr, old, new) != old);

arch/arm/include/asm/spinlock.h

+1 −1
Original line number Diff line number Diff line
@@ -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();

arch/arm/mach-tegra/cpuidle-tegra20.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/arm/vdso/vgettimeofday.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

arch/ia64/include/asm/spinlock.h

+4 −4
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) 


static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)

{

	int tmp = ACCESS_ONCE(lock->lock);

	int tmp = READ_ONCE(lock->lock);



	if (!(((tmp >> TICKET_SHIFT) ^ tmp) & TICKET_MASK))

		return ia64_cmpxchg(acq, &lock->lock, tmp, tmp + 1, sizeof (tmp)) == tmp;
@@ -73,19 +73,19 @@ static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock) 
	unsigned short	*p = (unsigned short *)&lock->lock + 1, tmp;



	asm volatile ("ld2.bias %0=[%1]" : "=r"(tmp) : "r"(p));

	ACCESS_ONCE(*p) = (tmp + 2) & ~1;

	WRITE_ONCE(*p, (tmp + 2) & ~1);

}



static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)

{

	long tmp = ACCESS_ONCE(lock->lock);

	long tmp = READ_ONCE(lock->lock);



	return !!(((tmp >> TICKET_SHIFT) ^ tmp) & TICKET_MASK);

}



static inline int __ticket_spin_is_contended(arch_spinlock_t *lock)

{

	long tmp = ACCESS_ONCE(lock->lock);

	long tmp = READ_ONCE(lock->lock);



	return ((tmp - (tmp >> TICKET_SHIFT)) & TICKET_MASK) > 1;

}

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