diff options
| author | Samiullah Khawaja <skhawaja@google.com> | 2025-08-04 16:44:57 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-08-05 17:46:15 -0700 |
| commit | e6d76268813dc64cc0b74ea9c274501f2de05344 (patch) | |
| tree | 218e1cfbecb545f3102d922197aa1028c6ba96a0 /net/core/dev.c | |
| parent | 8d22aea8af0d57a1daff046d65b7c18552e35e29 (diff) | |
net: Update threaded state in napi config in netif_set_threaded
Commit 2677010e7793 ("Add support to set NAPI threaded for individual
NAPI") added support to enable/disable threaded napi using netlink. This
also extended the napi config save/restore functionality to set the napi
threaded state. This breaks netdev reset for drivers that use napi
threaded at device level and also use napi config save/restore on
napi_disable/napi_enable. Basically on netdev with napi threaded enabled
at device level, a napi_enable call will get stuck trying to stop the
napi kthread. This is because the napi->config->threaded is set to
disabled when threaded is enabled at device level.
The issue can be reproduced on virtio-net device using qemu. To
reproduce the issue run following,
echo 1 > /sys/class/net/threaded
ethtool -L eth0 combined 1
Update the threaded state in napi config in netif_set_threaded and add a
new test that verifies this scenario.
Tested on qemu with virtio-net:
NETIF=eth0 ./tools/testing/selftests/drivers/net/napi_threaded.py
TAP version 13
1..2
ok 1 napi_threaded.change_num_queues
ok 2 napi_threaded.enable_dev_threaded_disable_napi_threaded
# Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0
Fixes: 2677010e7793 ("Add support to set NAPI threaded for individual NAPI")
Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
Link: https://patch.msgid.link/20250804164457.2494390-1-skhawaja@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/core/dev.c')
| -rw-r--r-- | net/core/dev.c | 26 |
1 files changed, 9 insertions, 17 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index b28ce68830b2..68dc47d7e700 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6978,6 +6978,12 @@ int napi_set_threaded(struct napi_struct *napi, if (napi->config) napi->config->threaded = threaded; + /* Setting/unsetting threaded mode on a napi might not immediately + * take effect, if the current napi instance is actively being + * polled. In this case, the switch between threaded mode and + * softirq mode will happen in the next round of napi_schedule(). + * This should not cause hiccups/stalls to the live traffic. + */ if (!threaded && napi->thread) { napi_stop_kthread(napi); } else { @@ -7011,23 +7017,9 @@ int netif_set_threaded(struct net_device *dev, WRITE_ONCE(dev->threaded, threaded); - /* Make sure kthread is created before THREADED bit - * is set. - */ - smp_mb__before_atomic(); - - /* Setting/unsetting threaded mode on a napi might not immediately - * take effect, if the current napi instance is actively being - * polled. In this case, the switch between threaded mode and - * softirq mode will happen in the next round of napi_schedule(). - * This should not cause hiccups/stalls to the live traffic. - */ - list_for_each_entry(napi, &dev->napi_list, dev_list) { - if (!threaded && napi->thread) - napi_stop_kthread(napi); - else - assign_bit(NAPI_STATE_THREADED, &napi->state, threaded); - } + /* The error should not occur as the kthreads are already created. */ + list_for_each_entry(napi, &dev->napi_list, dev_list) + WARN_ON_ONCE(napi_set_threaded(napi, threaded)); return err; } |