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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-10-24 00:07:25 +0300
committerIngo Molnar <mingo@kernel.org>2017-10-25 12:01:06 +0300
commitb03a0fe0c5e4b46dcd400d27395b124499554a71 (patch)
treed36452ac27e2f27487af9f930d7a54f3fa01f718 /mm
parent3587679d93d0b0e4c31e5a2ad1dffdfcb77e8526 (diff)
downloadlinux-b03a0fe0c5e4b46dcd400d27395b124499554a71.tar.xz
locking/atomics, mm: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_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 mm 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: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.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 Link: http://lkml.kernel.org/r/1508792849-3115-15-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memory.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c
index a728bed16c20..cae514e7dcfc 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3891,9 +3891,9 @@ static int handle_pte_fault(struct vm_fault *vmf)
/*
* some architectures can have larger ptes than wordsize,
* e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and
- * CONFIG_32BIT=y, so READ_ONCE or ACCESS_ONCE cannot guarantee
- * atomic accesses. The code below just needs a consistent
- * view for the ifs and we later double check anyway with the
+ * CONFIG_32BIT=y, so READ_ONCE cannot guarantee atomic
+ * accesses. The code below just needs a consistent view
+ * for the ifs and we later double check anyway with the
* ptl lock held. So here a barrier will do.
*/
barrier();