net: Use cpu_chill() instead of cpu_relax()

Retry loops on RT might loop forever when the modifying side was
preempted. Use cpu_chill() instead of cpu_relax() to let the system
make progress.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable-rt@vger.kernel.org

1 files changed, 3 insertions, 2 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d9d4970b9b07..ed8ef1eb2569 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -89,6 +89,7 @@
 #include <linux/virtio_net.h>
 #include <linux/errqueue.h>
 #include <linux/net_tstamp.h>
+#include <linux/delay.h>
 
 #ifdef CONFIG_INET
 #include <net/inet_common.h>
@@ -673,7 +674,7 @@ static void prb_retire_rx_blk_timer_expired(unsigned long data)
 	if (BLOCK_NUM_PKTS(pbd)) {
 		while (atomic_read(&pkc->blk_fill_in_prog)) {
 			/* Waiting for skb_copy_bits to finish... */
-			cpu_relax();
+			cpu_chill();
 		}
 	}
 
@@ -928,7 +929,7 @@ static void prb_retire_current_block(struct tpacket_kbdq_core *pkc,
 		if (!(status & TP_STATUS_BLK_TMO)) {
 			while (atomic_read(&pkc->blk_fill_in_prog)) {
 				/* Waiting for skb_copy_bits to finish... */
-				cpu_relax();
+				cpu_chill();
 			}
 		}
 		prb_close_block(pkc, pbd, po, status);