From 4d092dd2041a5f328410ad16d63b8606c24e8604 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 9 Sep 2020 10:37:52 -0700 Subject: [PATCH] net: manage napi add/del idempotence explicitly To RCUify napi->dev_list we need to replace list_del_init() with list_del_rcu(). There is no _init() version for RCU for obvious reasons. Up until now netif_napi_del() was idempotent so to make sure it remains such add a bit which is set when NAPI is listed, and cleared when it removed. Since we don't expect multiple calls to netif_napi_add() to be correct, add a warning on that side. Now that napi_hash_add / napi_hash_del are only called by napi_add / del we can actually steal its bit. We just need to make sure hash node is initialized correctly. Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller --- include/linux/netdevice.h | 4 ++-- net/core/dev.c | 13 +++++++++---- 2 files changed, 11 insertions(+), 6 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 74ed95215091..157e0242e9ee 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -355,7 +355,7 @@ enum { NAPI_STATE_MISSED, /* reschedule a napi */ NAPI_STATE_DISABLE, /* Disable pending */ NAPI_STATE_NPSVC, /* Netpoll - don't dequeue from poll_list */ - NAPI_STATE_HASHED, /* In NAPI hash (busy polling possible) */ + NAPI_STATE_LISTED, /* NAPI added to system lists */ NAPI_STATE_NO_BUSY_POLL,/* Do not add in napi_hash, no busy polling */ NAPI_STATE_IN_BUSY_POLL,/* sk_busy_loop() owns this NAPI */ }; @@ -365,7 +365,7 @@ enum { NAPIF_STATE_MISSED = BIT(NAPI_STATE_MISSED), NAPIF_STATE_DISABLE = BIT(NAPI_STATE_DISABLE), NAPIF_STATE_NPSVC = BIT(NAPI_STATE_NPSVC), - NAPIF_STATE_HASHED = BIT(NAPI_STATE_HASHED), + NAPIF_STATE_LISTED = BIT(NAPI_STATE_LISTED), NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL), NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL), }; diff --git a/net/core/dev.c b/net/core/dev.c index 205b7339d4ae..e0a1be986824 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6533,8 +6533,7 @@ EXPORT_SYMBOL(napi_busy_loop); static void napi_hash_add(struct napi_struct *napi) { - if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state) || - test_and_set_bit(NAPI_STATE_HASHED, &napi->state)) + if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state)) return; spin_lock(&napi_hash_lock); @@ -6559,8 +6558,7 @@ static void napi_hash_del(struct napi_struct *napi) { spin_lock(&napi_hash_lock); - if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state)) - hlist_del_rcu(&napi->napi_hash_node); + hlist_del_init_rcu(&napi->napi_hash_node); spin_unlock(&napi_hash_lock); } @@ -6595,7 +6593,11 @@ static void init_gro_hash(struct napi_struct *napi) void netif_napi_add(struct net_device *dev, struct napi_struct *napi, int (*poll)(struct napi_struct *, int), int weight) { + if (WARN_ON(test_and_set_bit(NAPI_STATE_LISTED, &napi->state))) + return; + INIT_LIST_HEAD(&napi->poll_list); + INIT_HLIST_NODE(&napi->napi_hash_node); hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED); napi->timer.function = napi_watchdog; init_gro_hash(napi); @@ -6650,6 +6652,9 @@ static void flush_gro_hash(struct napi_struct *napi) /* Must be called in process context */ void __netif_napi_del(struct napi_struct *napi) { + if (!test_and_clear_bit(NAPI_STATE_LISTED, &napi->state)) + return; + napi_hash_del(napi); list_del_init(&napi->dev_list); napi_free_frags(napi);