From ccba9f6baa900e31ad1a4c36e6f3c176694f9eac Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Fri, 8 Aug 2025 17:12:04 -0700 Subject: net: update NAPI threaded config even for disabled NAPIs We have to make sure that all future NAPIs will have the right threaded state when the state is configured on the device level. We chose not to have an "unset" state for threaded, and not to wipe the NAPI config clean when channels are explicitly disabled. This means the persistent config structs "exist" even when their NAPIs are not instantiated. Differently put - the NAPI persistent state lives in the net_device (ncfg == struct napi_config): ,--- [napi 0] - [napi 1] [dev] | | `--- [ncfg 0] - [ncfg 1] so say we a device with 2 queues but only 1 enabled: ,--- [napi 0] [dev] | `--- [ncfg 0] - [ncfg 1] now we set the device to threaded=1: ,---------- [napi 0 (thr:1)] [dev(thr:1)] | `---------- [ncfg 0 (thr:1)] - [ncfg 1 (thr:?)] Since [ncfg 1] was not attached to a NAPI during configuration we skipped it. If we create a NAPI for it later it will have the old setting (presumably disabled). One could argue if this is right or not "in principle", but it's definitely not how things worked before per-NAPI config.. Fixes: 2677010e7793 ("Add support to set NAPI threaded for individual NAPI") Signed-off-by: Jakub Kicinski Reviewed-by: Joe Damato Link: https://patch.msgid.link/20250809001205.1147153-3-kuba@kernel.org Signed-off-by: Paolo Abeni --- net/core/dev.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'net/core/dev.c') diff --git a/net/core/dev.c b/net/core/dev.c index 68dc47d7e700..f180746382a1 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6999,7 +6999,7 @@ int netif_set_threaded(struct net_device *dev, enum netdev_napi_threaded threaded) { struct napi_struct *napi; - int err = 0; + int i, err = 0; netdev_assert_locked_or_invisible(dev); @@ -7021,6 +7021,10 @@ int netif_set_threaded(struct net_device *dev, list_for_each_entry(napi, &dev->napi_list, dev_list) WARN_ON_ONCE(napi_set_threaded(napi, threaded)); + /* Override the config for all NAPIs even if currently not listed */ + for (i = 0; i < dev->num_napi_configs; i++) + dev->napi_config[i].threaded = threaded; + return err; } @@ -11873,6 +11877,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, goto free_all; dev->cfg_pending = dev->cfg; + dev->num_napi_configs = maxqs; napi_config_sz = array_size(maxqs, sizeof(*dev->napi_config)); dev->napi_config = kvzalloc(napi_config_sz, GFP_KERNEL_ACCOUNT); if (!dev->napi_config) -- cgit From b3fc08ab9a565efb42fe08be046a0d203b82cdb8 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Fri, 8 Aug 2025 17:12:05 -0700 Subject: net: prevent deadlocks when enabling NAPIs with mixed kthread config 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 Reviewed-by: Joe Damato Link: https://patch.msgid.link/20250809001205.1147153-4-kuba@kernel.org Signed-off-by: Paolo Abeni --- net/core/dev.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/core/dev.c') 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); -- cgit