Jakub Kicinski b3fc08ab9a 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: e6d7626881 ("net: Update threaded state in napi config in netif_set_threaded")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20250809001205.1147153-4-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-08-12 14:43:05 +02:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2024-03-18 03:36:32 -06:00

Linux kernel
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