Commit 74078816 authored by Paolo Abeni's avatar Paolo Abeni
Browse files

Merge branch 'net-prevent-deadlocks-and-mis-configuration-with-per-napi-threaded-config' 

Jakub Kicinski says:

====================
net: prevent deadlocks and mis-configuration with per-NAPI threaded config

Running the test added with a recent fix on a driver with persistent
NAPI config leads to a deadlock. The deadlock is fixed by patch 3,
patch 2 is I think a more fundamental problem with the way we
implemented the config.

I hope the fix makes sense, my own thinking is definitely colored
by my preference (IOW how the per-queue config RFC was implemented).

v1: https://lore.kernel.org/20250808014952.724762-1-kuba@kernel.org
====================

Link: https://patch.msgid.link/20250809001205.1147153-1-kuba@kernel.org


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parents e93f7af1 b3fc08ab

include/linux/netdevice.h

+4 −1
Original line number Diff line number Diff line
@@ -2071,6 +2071,8 @@ enum netdev_reg_state { 
 *	@max_pacing_offload_horizon: max EDT offload horizon in nsec.

 *	@napi_config: An array of napi_config structures containing per-NAPI

 *		      settings.

 *	@num_napi_configs:	number of allocated NAPI config structs,

 *		always >= max(num_rx_queues, num_tx_queues).

 *	@gro_flush_timeout:	timeout for GRO layer in NAPI

 *	@napi_defer_hard_irqs:	If not zero, provides a counter that would

 *				allow to avoid NIC hard IRQ, on busy queues.
@@ -2482,8 +2484,9 @@ struct net_device { 


	u64			max_pacing_offload_horizon;

	struct napi_config	*napi_config;

	unsigned long		gro_flush_timeout;

	u32			num_napi_configs;

	u32			napi_defer_hard_irqs;

	unsigned long		gro_flush_timeout;



	/**

	 * @up: copy of @state's IFF_UP, but safe to read with just @lock.

net/core/dev.c

+9 −3
Original line number Diff line number Diff line
@@ -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;

}
@@ -7353,7 +7357,8 @@ 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))

	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);

}
@@ -11873,6 +11878,7 @@ 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)

net/core/dev.h

+8 −0
Original line number Diff line number Diff line
@@ -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);

tools/testing/selftests/drivers/net/napi_threaded.py

+6 −4
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ def _setup_deferred_cleanup(cfg) -> None: 
    threaded = cmd(f"cat /sys/class/net/{cfg.ifname}/threaded").stdout

    defer(_set_threaded_state, cfg, threaded)



    return combined





def enable_dev_threaded_disable_napi_threaded(cfg, nl) -> None:

    """
@@ -49,7 +51,7 @@ def enable_dev_threaded_disable_napi_threaded(cfg, nl) -> None: 
    napi0_id = napis[0]['id']

    napi1_id = napis[1]['id']



    _setup_deferred_cleanup(cfg)

    qcnt = _setup_deferred_cleanup(cfg)



    # set threaded

    _set_threaded_state(cfg, 1)
@@ -62,7 +64,7 @@ def enable_dev_threaded_disable_napi_threaded(cfg, nl) -> None: 
    nl.napi_set({'id': napi1_id, 'threaded': 'disabled'})



    cmd(f"ethtool -L {cfg.ifname} combined 1")

    cmd(f"ethtool -L {cfg.ifname} combined 2")

    cmd(f"ethtool -L {cfg.ifname} combined {qcnt}")

    _assert_napi_threaded_enabled(nl, napi0_id)

    _assert_napi_threaded_disabled(nl, napi1_id)
@@ -80,7 +82,7 @@ def change_num_queues(cfg, nl) -> None: 
    napi0_id = napis[0]['id']

    napi1_id = napis[1]['id']



    _setup_deferred_cleanup(cfg)

    qcnt = _setup_deferred_cleanup(cfg)



    # set threaded

    _set_threaded_state(cfg, 1)
@@ -90,7 +92,7 @@ def change_num_queues(cfg, nl) -> None: 
    _assert_napi_threaded_enabled(nl, napi1_id)



    cmd(f"ethtool -L {cfg.ifname} combined 1")

    cmd(f"ethtool -L {cfg.ifname} combined 2")

    cmd(f"ethtool -L {cfg.ifname} combined {qcnt}")



    # check napi threaded is set for both napis

    _assert_napi_threaded_enabled(nl, napi0_id)