path: root/net
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authorJakub Kicinski <kuba@kernel.org>2020-09-09 10:37:51 -0700
committerDavid S. Miller <davem@davemloft.net>2020-09-10 13:08:46 -0700
commit5198d545dba8ad893f5e5a029ca8d43ee7bcf011 (patch)
treec06ec2bb85e93be90c7d71026c0d2affb984fcd6 /net
parentMerge branch 'mlx4-avoid-devlink-port-type-not-set-warnings' (diff)
net: remove napi_hash_del() from driver-facing API
We allow drivers to call napi_hash_del() before calling netif_napi_del() to batch RCU grace periods. This makes the API asymmetric and leaks internal implementation details. Soon we will want the grace period to protect more than just the NAPI hash table. Restructure the API and have drivers call a new function - __netif_napi_del() if they want to take care of RCU waits. Note that only core was checking the return status from napi_hash_del() so the new helper does not report if the NAPI was actually deleted. Some notes on driver oddness: - veth observed the grace period before calling netif_napi_del() but that should not matter - myri10ge observed normal RCU flavor - bnx2x and enic did not actually observe the grace period (unless they did so implicitly) - virtio_net and enic only unhashed Rx NAPIs The last two points seem to indicate that the calls to napi_hash_del() were a left over rather than an optimization. Regardless, it's easy enough to correct them. This patch may introduce extra synchronize_net() calls for interfaces which set NAPI_STATE_NO_BUSY_POLL and depend on free_netdev() to call netif_napi_del(). This seems inevitable since we want to use RCU for netpoll dev->napi_list traversal, and almost no drivers set IFF_DISABLE_NETPOLL. Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 6 insertions, 13 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index 152ad3b578de..205b7339d4ae 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6555,20 +6555,15 @@ static void napi_hash_add(struct napi_struct *napi)
/* Warning : caller is responsible to make sure rcu grace period
* is respected before freeing memory containing @napi
-bool napi_hash_del(struct napi_struct *napi)
+static void napi_hash_del(struct napi_struct *napi)
- bool rcu_sync_needed = false;
- if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state)) {
- rcu_sync_needed = true;
+ if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state))
- }
- return rcu_sync_needed;
static enum hrtimer_restart napi_watchdog(struct hrtimer *timer)
@@ -6653,18 +6648,16 @@ static void flush_gro_hash(struct napi_struct *napi)
/* Must be called in process context */
-void netif_napi_del(struct napi_struct *napi)
+void __netif_napi_del(struct napi_struct *napi)
- might_sleep();
- if (napi_hash_del(napi))
- synchronize_net();
+ napi_hash_del(napi);
napi->gro_bitmask = 0;
static int napi_poll(struct napi_struct *n, struct list_head *repoll)