wireguard: send/receive: cond_resched() when processing worker ringbuffers

Users with pathological hardware reported CPU stalls on CONFIG_
PREEMPT_VOLUNTARY=y, because the ringbuffers would stay full, meaning
these workers would never terminate. That turned out not to be okay on
systems without forced preemption, which Sultan observed. This commit
adds a cond_resched() to the bottom of each loop iteration, so that
these workers don't hog the core. Note that we don't need this on the
napi poll worker, since that terminates after its budget is expended.

Suggested-by: Sultan Alsawaf <sultan@kerneltoast.com>
Reported-by: Wang Jian <larkwang@gmail.com>
Fixes: 0c73bbc77a76 ("net: WireGuard secure network tunnel")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c
index 267f202f19314ce8dc58d17667336e6282ba598c..2566e13a292dee09c7784d5e71832e252b248b7f 100644 (file)
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -516,6 +516,8 @@ void wg_packet_decrypt_worker(struct work_struct *work)
                                &PACKET_CB(skb)->keypair->receiving)) ?
                                PACKET_STATE_CRYPTED : PACKET_STATE_DEAD;
                wg_queue_enqueue_per_peer_napi(skb, state);
+               if (need_resched())
+                       cond_resched();
        }
 }
 

diff --git a/drivers/net/wireguard/send.c b/drivers/net/wireguard/send.c
index 3e030d614df5f50671a7bc9e4ec0cbcd864d5956..dc3079e17c7fc6abef5d69853e9bc8adb5465a08 100644 (file)
--- a/drivers/net/wireguard/send.c
+++ b/drivers/net/wireguard/send.c
@@ -281,6 +281,8 @@ void wg_packet_tx_worker(struct work_struct *work)
 
                wg_noise_keypair_put(keypair, false);
                wg_peer_put(peer);
+               if (need_resched())
+                       cond_resched();
        }
 }
 
@@ -304,6 +306,8 @@ void wg_packet_encrypt_worker(struct work_struct *work)
                }
                wg_queue_enqueue_per_peer(&PACKET_PEER(first)->tx_queue, first,
                                          state);
+               if (need_resched())
+                       cond_resched();
        }
 }