locking/atomics, EDAC/altera: 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 Altera EDAC 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 <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Thor Thayer <thor.thayer@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
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: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-2-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/edac/altera_edac.c b/drivers/edac/altera_edac.c
index 346c4987b2848782336db887150b88db1a9b91a4..11d6419788c2d45eb467c3fb53614236e112d248 100644 (file)
--- a/drivers/edac/altera_edac.c
+++ b/drivers/edac/altera_edac.c
@@ -175,11 +175,11 @@ static ssize_t altr_sdr_mc_err_inject_write(struct file *file,
        /*
         * To trigger the error, we need to read the data back
         * (the data was written with errors above).
-        * The ACCESS_ONCE macros and printk are used to prevent the
+        * The READ_ONCE macros and printk are used to prevent the
         * the compiler optimizing these reads out.
         */
-       reg = ACCESS_ONCE(ptemp[0]);
-       read_reg = ACCESS_ONCE(ptemp[1]);
+       reg = READ_ONCE(ptemp[0]);
+       read_reg = READ_ONCE(ptemp[1]);
        /* Force Read */
        rmb();
 
@@ -618,7 +618,7 @@ static ssize_t altr_edac_device_trig(struct file *file,
        for (i = 0; i < (priv->trig_alloc_sz / sizeof(*ptemp)); i++) {
                /* Read data so we're in the correct state */
                rmb();
-               if (ACCESS_ONCE(ptemp[i]))
+               if (READ_ONCE(ptemp[i]))
                        result = -1;
                /* Toggle Error bit (it is latched), leave ECC enabled */
                writel(error_mask, (drvdata->base + priv->set_err_ofst));
@@ -635,7 +635,7 @@ static ssize_t altr_edac_device_trig(struct file *file,
 
        /* Read out written data. ECC error caused here */
        for (i = 0; i < ALTR_TRIGGER_READ_WRD_CNT; i++)
-               if (ACCESS_ONCE(ptemp[i]) != i)
+               if (READ_ONCE(ptemp[i]) != i)
                        edac_printk(KERN_ERR, EDAC_DEVICE,
                                    "Read doesn't match written data\n");