The following order of calls currently deadlocks if: - device has threaded=1; and - NAPI has persistent config with threaded=0.
netif_napi_add_weight_config() dev->threaded == 1 napi_kthread_create()
napi_enable() napi_restore_config() napi_set_threaded(0) napi_stop_kthread() while (NAPIF_STATE_SCHED) msleep(20)
We deadlock because disabled NAPI has STATE_SCHED set. Creating a thread in netif_napi_add() just to destroy it in napi_disable() is fairly ugly in the first place. Let's read both the device config and the NAPI config in netif_napi_add().
Fixes: e6d76268813d ("net: Update threaded state in napi config in netif_set_threaded") Signed-off-by: Jakub Kicinski kuba@kernel.org --- net/core/dev.h | 8 ++++++++ net/core/dev.c | 5 +++-- 2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/net/core/dev.h b/net/core/dev.h index ab69edc0c3e3..d6b08d435479 100644 --- a/net/core/dev.h +++ b/net/core/dev.h @@ -323,6 +323,14 @@ static inline enum netdev_napi_threaded napi_get_threaded(struct napi_struct *n) return NETDEV_NAPI_THREADED_DISABLED; }
+static inline enum netdev_napi_threaded +napi_get_threaded_config(struct net_device *dev, struct napi_struct *n) +{ + if (n->config) + return n->config->threaded; + return dev->threaded; +} + int napi_set_threaded(struct napi_struct *n, enum netdev_napi_threaded threaded);
diff --git a/net/core/dev.c b/net/core/dev.c index f180746382a1..5a3c0f40a93f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -7357,8 +7357,9 @@ void netif_napi_add_weight_locked(struct net_device *dev, * Clear dev->threaded if kthread creation failed so that * threaded mode will not be enabled in napi_enable(). */ - if (dev->threaded && napi_kthread_create(napi)) - dev->threaded = NETDEV_NAPI_THREADED_DISABLED; + if (napi_get_threaded_config(dev, napi)) + if (napi_kthread_create(napi)) + dev->threaded = NETDEV_NAPI_THREADED_DISABLED; netif_napi_set_irq_locked(napi, -1); } EXPORT_SYMBOL(netif_napi_add_weight_locked);