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[PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown

Stanislav Fomichev posted 1 patch 8 months, 3 weeks ago 
drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 ++
1 file changed, 2 insertions(+)
[PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown
Posted by Stanislav Fomichev 8 months, 3 weeks ago 
Taehee reports missing rtnl from bnxt_shutdown path:

inetdev_event (./include/linux/inetdevice.h:256 net/ipv4/devinet.c:1585)
notifier_call_chain (kernel/notifier.c:85)
__dev_close_many (net/core/dev.c:1732 (discriminator 3))
kernel/locking/mutex.c:713 kernel/locking/mutex.c:732)
dev_close_many (net/core/dev.c:1786)
netif_close (./include/linux/list.h:124 ./include/linux/list.h:215
bnxt_shutdown (drivers/net/ethernet/broadcom/bnxt/bnxt.c:16707) bnxt_en
pci_device_shutdown (drivers/pci/pci-driver.c:511)
device_shutdown (drivers/base/core.c:4820)
kernel_restart (kernel/reboot.c:271 kernel/reboot.c:285)

Bring back the rtnl lock.

Link: https://lore.kernel.org/netdev/CAMArcTV4P8PFsc6O2tSgzRno050DzafgqkLA2b7t=Fv_SY=brw@mail.gmail.com/
Fixes: 004b5008016a ("eth: bnxt: remove most dependencies on RTNL")
Reported-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 934ba9425857..1a70605fad38 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -16698,6 +16698,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
 	if (!dev)
 		return;
 
+	rtnl_lock();
 	netdev_lock(dev);
 	bp = netdev_priv(dev);
 	if (!bp)
@@ -16717,6 +16718,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
 
 shutdown_exit:
 	netdev_unlock(dev);
+	rtnl_unlock();
 }
 
 #ifdef CONFIG_PM_SLEEP
-- 
2.48.1
Re: [PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown
Posted by Breno Leitao 8 months, 2 weeks ago 
Hello Stanislav,

On Fri, Mar 28, 2025 at 10:42:16AM -0700, Stanislav Fomichev wrote:
> Taehee reports missing rtnl from bnxt_shutdown path:
> 
> inetdev_event (./include/linux/inetdevice.h:256 net/ipv4/devinet.c:1585)
> notifier_call_chain (kernel/notifier.c:85)
> __dev_close_many (net/core/dev.c:1732 (discriminator 3))
> kernel/locking/mutex.c:713 kernel/locking/mutex.c:732)
> dev_close_many (net/core/dev.c:1786)
> netif_close (./include/linux/list.h:124 ./include/linux/list.h:215
> bnxt_shutdown (drivers/net/ethernet/broadcom/bnxt/bnxt.c:16707) bnxt_en
> pci_device_shutdown (drivers/pci/pci-driver.c:511)
> device_shutdown (drivers/base/core.c:4820)
> kernel_restart (kernel/reboot.c:271 kernel/reboot.c:285)

I've got this issue as well.

> 
> Bring back the rtnl lock.
> 
> Link: https://lore.kernel.org/netdev/CAMArcTV4P8PFsc6O2tSgzRno050DzafgqkLA2b7t=Fv_SY=brw@mail.gmail.com/
> Fixes: 004b5008016a ("eth: bnxt: remove most dependencies on RTNL")
> Reported-by: Taehee Yoo <ap420073@gmail.com>
> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>

Tested-by: Breno Leitao <leitao@debian.org>

> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 934ba9425857..1a70605fad38 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -16698,6 +16698,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
>  	if (!dev)
>  		return;
>  
> +	rtnl_lock();
>  	netdev_lock(dev);

can't we leverage the `struct net_device->lock` for the shutdown.
Basically we have the lock the single device we are turning it down.

I am wondering if we really need the big RTNL lock. This is my
understanding of what is happening:

pci_device_shutdown() is called for a single device
 - netdev_lock(dev)
 - netif_close(dev);
    - dev_close_many(&single, true);
      - __dev_close_many()
        - ASSERT_RTNL();

Basically we ware only closing one device, and the net_device->lock
is already held. Shouldn't it be enough?

Can we do something like this (from my naive point of view):

	 static void __dev_close_many(struct list_head *head)
	  {
		  struct net_device *dev;

	-         ASSERT_RTNL();
		  might_sleep();

		  list_for_each_entry(dev, head, close_list) {
	+	  	ASSERT_RTNL_NET(dev);
			...
		  }

Thanks
--breno
Re: [PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown
Posted by Stanislav Fomichev 8 months, 2 weeks ago 
On 03/31, Breno Leitao wrote:
> Hello Stanislav,
> 
> On Fri, Mar 28, 2025 at 10:42:16AM -0700, Stanislav Fomichev wrote:
> > Taehee reports missing rtnl from bnxt_shutdown path:
> > 
> > inetdev_event (./include/linux/inetdevice.h:256 net/ipv4/devinet.c:1585)
> > notifier_call_chain (kernel/notifier.c:85)
> > __dev_close_many (net/core/dev.c:1732 (discriminator 3))
> > kernel/locking/mutex.c:713 kernel/locking/mutex.c:732)
> > dev_close_many (net/core/dev.c:1786)
> > netif_close (./include/linux/list.h:124 ./include/linux/list.h:215
> > bnxt_shutdown (drivers/net/ethernet/broadcom/bnxt/bnxt.c:16707) bnxt_en
> > pci_device_shutdown (drivers/pci/pci-driver.c:511)
> > device_shutdown (drivers/base/core.c:4820)
> > kernel_restart (kernel/reboot.c:271 kernel/reboot.c:285)
> 
> I've got this issue as well.
> 
> > 
> > Bring back the rtnl lock.
> > 
> > Link: https://lore.kernel.org/netdev/CAMArcTV4P8PFsc6O2tSgzRno050DzafgqkLA2b7t=Fv_SY=brw@mail.gmail.com/
> > Fixes: 004b5008016a ("eth: bnxt: remove most dependencies on RTNL")
> > Reported-by: Taehee Yoo <ap420073@gmail.com>
> > Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
> 
> Tested-by: Breno Leitao <leitao@debian.org>
> 
> > ---
> >  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > index 934ba9425857..1a70605fad38 100644
> > --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > @@ -16698,6 +16698,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
> >  	if (!dev)
> >  		return;
> >  
> > +	rtnl_lock();
> >  	netdev_lock(dev);
> 
> can't we leverage the `struct net_device->lock` for the shutdown.
> Basically we have the lock the single device we are turning it down.
> 
> I am wondering if we really need the big RTNL lock. This is my
> understanding of what is happening:
> 
> pci_device_shutdown() is called for a single device
>  - netdev_lock(dev)
>  - netif_close(dev);
>     - dev_close_many(&single, true);
>       - __dev_close_many()
>         - ASSERT_RTNL();
> 
> Basically we ware only closing one device, and the net_device->lock
> is already held. Shouldn't it be enough?

[..]

> Can we do something like this (from my naive point of view):
> 
> 	 static void __dev_close_many(struct list_head *head)
> 	  {
> 		  struct net_device *dev;
> 
> 	-         ASSERT_RTNL();
> 		  might_sleep();
> 
> 		  list_for_each_entry(dev, head, close_list) {
> 	+	  	ASSERT_RTNL_NET(dev);
> 			...
> 		  }

- netif_close adds dev->close_list to the list (if it was up)
- __dev_close_many walks over that list, so your new assert should
  trigger as well

But also in general, it would be nice to keep existing
rtnl+instance_lock scheme for now (except were we want to explicitly opt
out, as in queue apis); we can follow up later to un-rtnl the rest.
Re: [PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown
Posted by Breno Leitao 8 months, 2 weeks ago 
On Mon, Mar 31, 2025 at 08:29:53AM -0700, Stanislav Fomichev wrote:
> On 03/31, Breno Leitao wrote:
> > Hello Stanislav,
> > 
> > On Fri, Mar 28, 2025 at 10:42:16AM -0700, Stanislav Fomichev wrote:
> > > Taehee reports missing rtnl from bnxt_shutdown path:
> > > 
> > > inetdev_event (./include/linux/inetdevice.h:256 net/ipv4/devinet.c:1585)
> > > notifier_call_chain (kernel/notifier.c:85)
> > > __dev_close_many (net/core/dev.c:1732 (discriminator 3))
> > > kernel/locking/mutex.c:713 kernel/locking/mutex.c:732)
> > > dev_close_many (net/core/dev.c:1786)
> > > netif_close (./include/linux/list.h:124 ./include/linux/list.h:215
> > > bnxt_shutdown (drivers/net/ethernet/broadcom/bnxt/bnxt.c:16707) bnxt_en
> > > pci_device_shutdown (drivers/pci/pci-driver.c:511)
> > > device_shutdown (drivers/base/core.c:4820)
> > > kernel_restart (kernel/reboot.c:271 kernel/reboot.c:285)
> > 
> > I've got this issue as well.
> > 
> > > 
> > > Bring back the rtnl lock.
> > > 
> > > Link: https://lore.kernel.org/netdev/CAMArcTV4P8PFsc6O2tSgzRno050DzafgqkLA2b7t=Fv_SY=brw@mail.gmail.com/
> > > Fixes: 004b5008016a ("eth: bnxt: remove most dependencies on RTNL")
> > > Reported-by: Taehee Yoo <ap420073@gmail.com>
> > > Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
> > 
> > Tested-by: Breno Leitao <leitao@debian.org>
> > 
> > > ---
> > >  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > > index 934ba9425857..1a70605fad38 100644
> > > --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > > +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > > @@ -16698,6 +16698,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
> > >  	if (!dev)
> > >  		return;
> > >  
> > > +	rtnl_lock();
> > >  	netdev_lock(dev);
> > 
> > can't we leverage the `struct net_device->lock` for the shutdown.
> > Basically we have the lock the single device we are turning it down.
> > 
> > I am wondering if we really need the big RTNL lock. This is my
> > understanding of what is happening:
> > 
> > pci_device_shutdown() is called for a single device
> >  - netdev_lock(dev)
> >  - netif_close(dev);
> >     - dev_close_many(&single, true);
> >       - __dev_close_many()
> >         - ASSERT_RTNL();
> > 
> > Basically we ware only closing one device, and the net_device->lock
> > is already held. Shouldn't it be enough?
> 
> [..]
> 
> > Can we do something like this (from my naive point of view):
> > 
> > 	 static void __dev_close_many(struct list_head *head)
> > 	  {
> > 		  struct net_device *dev;
> > 
> > 	-         ASSERT_RTNL();
> > 		  might_sleep();
> > 
> > 		  list_for_each_entry(dev, head, close_list) {
> > 	+	  	ASSERT_RTNL_NET(dev);
> > 			...
> > 		  }
> 
> - netif_close adds dev->close_list to the list (if it was up)

Right, but that list has only one net_device entry, right?

netif_close() instanciates a single list and merges it into `dev->close_list`

> - __dev_close_many walks over that list, so your new assert should
>   trigger as well

Why? Isn't the list only contain the dev that is already protected by
netdev_lock()?

> But also in general, it would be nice to keep existing
> rtnl+instance_lock scheme for now (except were we want to explicitly opt
> out, as in queue apis); we can follow up later to un-rtnl the rest.

I am just wondering if the code as-is is already safe from a locking
perspecting, and just the warning (ASSERT_RTNL) is wrong.
Re: [PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown
Posted by Jakub Kicinski 8 months, 2 weeks ago 
On Mon, 31 Mar 2025 09:53:16 -0700 Breno Leitao wrote:
> > But also in general, it would be nice to keep existing
> > rtnl+instance_lock scheme for now (except were we want to explicitly opt
> > out, as in queue apis); we can follow up later to un-rtnl the rest.  
> 
> I am just wondering if the code as-is is already safe from a locking
> perspecting, and just the warning (ASSERT_RTNL) is wrong.

I suspect the notifiers for DOWN may expect to be called with rtnl held.
Re: [PATCH net] bnxt_en: bring back rtnl lock in bnxt_shutdown
Posted by Taehee Yoo 8 months, 3 weeks ago 
On Sat, Mar 29, 2025 at 2:42 AM Stanislav Fomichev <sdf@fomichev.me> wrote:
>

Hi Stanislav,
Thanks a lot for this fix!

> Taehee reports missing rtnl from bnxt_shutdown path:
>
> inetdev_event (./include/linux/inetdevice.h:256 net/ipv4/devinet.c:1585)
> notifier_call_chain (kernel/notifier.c:85)
> __dev_close_many (net/core/dev.c:1732 (discriminator 3))
> kernel/locking/mutex.c:713 kernel/locking/mutex.c:732)
> dev_close_many (net/core/dev.c:1786)
> netif_close (./include/linux/list.h:124 ./include/linux/list.h:215
> bnxt_shutdown (drivers/net/ethernet/broadcom/bnxt/bnxt.c:16707) bnxt_en
> pci_device_shutdown (drivers/pci/pci-driver.c:511)
> device_shutdown (drivers/base/core.c:4820)
> kernel_restart (kernel/reboot.c:271 kernel/reboot.c:285)
>
> Bring back the rtnl lock.

Tested-by: Taehee Yoo <ap420073@gmail.com>

>
> Link: https://lore.kernel.org/netdev/CAMArcTV4P8PFsc6O2tSgzRno050DzafgqkLA2b7t=Fv_SY=brw@mail.gmail.com/
> Fixes: 004b5008016a ("eth: bnxt: remove most dependencies on RTNL")
> Reported-by: Taehee Yoo <ap420073@gmail.com>
> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 934ba9425857..1a70605fad38 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -16698,6 +16698,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
>         if (!dev)
>                 return;
>
> +       rtnl_lock();
>         netdev_lock(dev);
>         bp = netdev_priv(dev);
>         if (!bp)
> @@ -16717,6 +16718,7 @@ static void bnxt_shutdown(struct pci_dev *pdev)
>
>  shutdown_exit:
>         netdev_unlock(dev);
> +       rtnl_unlock();
>  }
>
>  #ifdef CONFIG_PM_SLEEP
> --
> 2.48.1
>

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