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From: Leon Romanovsky <leon@kernel.org>
To: Ivan Vecera <ivecera@redhat.com>
Cc: SlawomirX Laba <slawomirx.laba@intel.com>,
	Eric Dumazet <edumazet@google.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	"Piotrowski, Patryk" <patryk.piotrowski@intel.com>,
	"moderated list:INTEL ETHERNET DRIVERS"
	<intel-wired-lan@lists.osuosl.org>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	"sassmann@redhat.com" <sassmann@redhat.com>
Subject: Re: [Intel-wired-lan] [PATCH net] iavf: Do not restart Tx queues after reset task failure
Date: Thu, 10 Nov 2022 19:07:02 +0200	[thread overview]
Message-ID: <Y20vtqd6raqg8iwy@unreal> (raw)
In-Reply-To: <20221110155147.1a2c57f6@p1.luc.cera.cz>

On Thu, Nov 10, 2022 at 03:51:47PM +0100, Ivan Vecera wrote:
> On Wed, 9 Nov 2022 20:11:55 +0000
> "Keller, Jacob E" <jacob.e.keller@intel.com> wrote:
> 
> > > Sorry for my naive question, I see this pattern a lot (including RDMA),
> > > so curious. Everyone checks netif_running() outside of rtnl_lock, while
> > > dev_close() changes state bit __LINK_STATE_START. Shouldn't rtnl_lock()
> > > placed before netif_running()?  
> > 
> > Yes I think you're right. A ton of people check it without the lock but I think thats not strictly safe. Is dev_close safe to call when netif_running is false? Why not just remove the check and always call dev_close then.
> > 
> > Thanks,
> > Jake
> 
> Check for a bit value (like netif_runnning()) is much cheaper than unconditionally
> taking global lock like RTNL.

This cheap operation is racy and performed in non-performance critical path.

Thanks

> 
> Ivan
> 
_______________________________________________
Intel-wired-lan mailing list
Intel-wired-lan@osuosl.org
https://lists.osuosl.org/mailman/listinfo/intel-wired-lan

WARNING: multiple messages have this Message-ID (diff)
From: Leon Romanovsky <leon@kernel.org>
To: Ivan Vecera <ivecera@redhat.com>
Cc: "Keller, Jacob E" <jacob.e.keller@intel.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"sassmann@redhat.com" <sassmann@redhat.com>,
	"Piotrowski, Patryk" <patryk.piotrowski@intel.com>,
	SlawomirX Laba <slawomirx.laba@intel.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@intel.com>,
	"Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	"moderated list:INTEL ETHERNET DRIVERS" 
	<intel-wired-lan@lists.osuosl.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] iavf: Do not restart Tx queues after reset task failure
Date: Thu, 10 Nov 2022 19:07:02 +0200	[thread overview]
Message-ID: <Y20vtqd6raqg8iwy@unreal> (raw)
In-Reply-To: <20221110155147.1a2c57f6@p1.luc.cera.cz>

On Thu, Nov 10, 2022 at 03:51:47PM +0100, Ivan Vecera wrote:
> On Wed, 9 Nov 2022 20:11:55 +0000
> "Keller, Jacob E" <jacob.e.keller@intel.com> wrote:
> 
> > > Sorry for my naive question, I see this pattern a lot (including RDMA),
> > > so curious. Everyone checks netif_running() outside of rtnl_lock, while
> > > dev_close() changes state bit __LINK_STATE_START. Shouldn't rtnl_lock()
> > > placed before netif_running()?  
> > 
> > Yes I think you're right. A ton of people check it without the lock but I think thats not strictly safe. Is dev_close safe to call when netif_running is false? Why not just remove the check and always call dev_close then.
> > 
> > Thanks,
> > Jake
> 
> Check for a bit value (like netif_runnning()) is much cheaper than unconditionally
> taking global lock like RTNL.

This cheap operation is racy and performed in non-performance critical path.

Thanks

> 
> Ivan
> 

  reply	other threads:[~2022-11-10 17:07 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-08 10:25 [Intel-wired-lan] [PATCH net] iavf: Do not restart Tx queues after reset task failure Ivan Vecera
2022-11-08 10:25 ` Ivan Vecera
2022-11-08 16:40 ` [Intel-wired-lan] " Jacob Keller
2022-11-08 16:40   ` Jacob Keller
2022-11-09 18:20 ` [Intel-wired-lan] " Leon Romanovsky
2022-11-09 18:20   ` Leon Romanovsky
2022-11-09 20:11   ` [Intel-wired-lan] " Keller, Jacob E
2022-11-09 20:11     ` Keller, Jacob E
2022-11-10  9:17     ` [Intel-wired-lan] " Leon Romanovsky
2022-11-10  9:17       ` Leon Romanovsky
2022-11-10 14:51     ` [Intel-wired-lan] " Ivan Vecera
2022-11-10 14:51       ` Ivan Vecera
2022-11-10 17:07       ` Leon Romanovsky [this message]
2022-11-10 17:07         ` Leon Romanovsky
2022-11-10 20:24         ` [Intel-wired-lan] " Jakub Kicinski
2022-11-10 21:07           ` Leon Romanovsky
2022-11-10 21:07             ` Leon Romanovsky
2022-11-10 21:13             ` [Intel-wired-lan] " Keller, Jacob E
2022-11-10 21:13               ` Keller, Jacob E
2022-11-18 14:30 ` [Intel-wired-lan] " Jankowski, Konrad0
2022-11-18 14:30   ` Jankowski, Konrad0
2022-11-18 14:31 ` Jankowski, Konrad0
2022-11-18 14:31   ` Jankowski, Konrad0

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