[PATCH 7/7] xen/evtchn: read producer index only once

Juergen Gross
2021-02-06T10:53:52Z

In evtchn_read() use READ_ONCE() for reading the producer index in
order to avoid the compiler generating multiple accesses.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
drivers/xen/evtchn.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index 421382c73d88..f6b199b597bf 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -211,7 +211,7 @@ static ssize_t evtchn_read(struct file *file, char __user *buf,
goto unlock_out;

c = u->ring_cons;
- p = u->ring_prod;
+ p = READ_ONCE(u->ring_prod);
if (c != p)
break;

--
2.26.2