target/linux/generic/backport-5.4/080-wireguard-0099-wireguard-send-receive-cond_resched-when-processing-.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: "Jason A. Donenfeld" <Jason@zx2c4.com>
   3 Date: Wed, 6 May 2020 15:33:04 -0600
   4 Subject: [PATCH] wireguard: send/receive: cond_resched() when processing
   5  worker ringbuffers
   6
   7 commit 4005f5c3c9d006157ba716594e0d70c88a235c5e upstream.
   8
   9 Users with pathological hardware reported CPU stalls on CONFIG_
  10 PREEMPT_VOLUNTARY=y, because the ringbuffers would stay full, meaning
  11 these workers would never terminate. That turned out not to be okay on
  12 systems without forced preemption, which Sultan observed. This commit
  13 adds a cond_resched() to the bottom of each loop iteration, so that
  14 these workers don't hog the core. Note that we don't need this on the
  15 napi poll worker, since that terminates after its budget is expended.
  16
  17 Suggested-by: Sultan Alsawaf <sultan@kerneltoast.com>
  18 Reported-by: Wang Jian <larkwang@gmail.com>
  19 Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
  20 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  21 Signed-off-by: David S. Miller <davem@davemloft.net>
  22 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  23 ---
  24  drivers/net/wireguard/receive.c | 2 ++
  25  drivers/net/wireguard/send.c    | 4 ++++
  26  2 files changed, 6 insertions(+)
  27
  28 --- a/drivers/net/wireguard/receive.c
  29 +++ b/drivers/net/wireguard/receive.c
  30 @@ -516,6 +516,8 @@ void wg_packet_decrypt_worker(struct wor
  31                                 &PACKET_CB(skb)->keypair->receiving)) ?
  32                                 PACKET_STATE_CRYPTED : PACKET_STATE_DEAD;
  33                 wg_queue_enqueue_per_peer_napi(skb, state);
  34 +               if (need_resched())
  35 +                       cond_resched();
  36         }
  37  }
  38
  39 --- a/drivers/net/wireguard/send.c
  40 +++ b/drivers/net/wireguard/send.c
  41 @@ -281,6 +281,8 @@ void wg_packet_tx_worker(struct work_str
  42
  43                 wg_noise_keypair_put(keypair, false);
  44                 wg_peer_put(peer);
  45 +               if (need_resched())
  46 +                       cond_resched();
  47         }
  48  }
  49
  50 @@ -304,6 +306,8 @@ void wg_packet_encrypt_worker(struct wor
  51                 }
  52                 wg_queue_enqueue_per_peer(&PACKET_PEER(first)->tx_queue, first,
  53                                           state);
  54 +               if (need_resched())
  55 +                       cond_resched();
  56         }
  57  }
  58