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locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

Browse source 
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 <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Mark Rutland 2017-10-23 14:07:29 -07:00 • committed by Ingo Molnar
commit 6aa7de0591
180 changed files with 383 additions and 385 deletions
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4
kernel/acct.c
View file

@ -146,7 +146,7 @@ static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
again:
smp_rmb();
rcu_read_lock();
res = to_acct(ACCESS_ONCE(ns->bacct));
res = to_acct(READ_ONCE(ns->bacct));
if (!res) {
rcu_read_unlock();
return NULL;
@ -158,7 +158,7 @@ again:
}
rcu_read_unlock();
mutex_lock(&res->lock);
if (res != to_acct(ACCESS_ONCE(ns->bacct))) {
if (res != to_acct(READ_ONCE(ns->bacct))) {
mutex_unlock(&res->lock);
acct_put(res);
goto again;