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From: Amol Grover <frextrite@gmail.com>
To: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S . Miller" <davem@davemloft.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	brouer@redhat.com, toke@redhat.com
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Joel Fernandes <joel@joelfernandes.org>,
	Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH] bpf: devmap: Pass lockdep expression to RCU lists
Date: Thu, 23 Jan 2020 22:48:00 +0530	[thread overview]
Message-ID: <20200123171800.GC4484@workstation-portable> (raw)
In-Reply-To: <20200123120437.26506-1-frextrite@gmail.com>

On Thu, Jan 23, 2020 at 05:34:38PM +0530, Amol Grover wrote:
> head is traversed using hlist_for_each_entry_rcu outside an
> RCU read-side critical section but under the protection
> of dtab->index_lock.
> 
> Hence, add corresponding lockdep expression to silence false-positive
> lockdep warnings, and harden RCU lists.
> 
Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
> Signed-off-by: Amol Grover <frextrite@gmail.com>
> ---
>  kernel/bpf/devmap.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 3d3d61b5985b..b4b6b77f309c 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -293,7 +293,8 @@ struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
>  	struct hlist_head *head = dev_map_index_hash(dtab, key);
>  	struct bpf_dtab_netdev *dev;
>  
> -	hlist_for_each_entry_rcu(dev, head, index_hlist)
> +	hlist_for_each_entry_rcu(dev, head, index_hlist,
> +				 lockdep_is_held(&dtab->index_lock))
>  		if (dev->idx == key)
>  			return dev;
>  
> -- 
> 2.24.1
> 

WARNING: multiple messages have this Message-ID (diff)
From: Amol Grover <frextrite@gmail.com>
To: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S . Miller" <davem@davemloft.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	brouer@redhat.com, toke@redhat.com
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Joel Fernandes <joel@joelfernandes.org>,
	bpf@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [Linux-kernel-mentees] [PATCH] bpf: devmap: Pass lockdep expression to RCU lists
Date: Thu, 23 Jan 2020 22:48:00 +0530	[thread overview]
Message-ID: <20200123171800.GC4484@workstation-portable> (raw)
In-Reply-To: <20200123120437.26506-1-frextrite@gmail.com>

On Thu, Jan 23, 2020 at 05:34:38PM +0530, Amol Grover wrote:
> head is traversed using hlist_for_each_entry_rcu outside an
> RCU read-side critical section but under the protection
> of dtab->index_lock.
> 
> Hence, add corresponding lockdep expression to silence false-positive
> lockdep warnings, and harden RCU lists.
> 
Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
> Signed-off-by: Amol Grover <frextrite@gmail.com>
> ---
>  kernel/bpf/devmap.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 3d3d61b5985b..b4b6b77f309c 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -293,7 +293,8 @@ struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
>  	struct hlist_head *head = dev_map_index_hash(dtab, key);
>  	struct bpf_dtab_netdev *dev;
>  
> -	hlist_for_each_entry_rcu(dev, head, index_hlist)
> +	hlist_for_each_entry_rcu(dev, head, index_hlist,
> +				 lockdep_is_held(&dtab->index_lock))
>  		if (dev->idx == key)
>  			return dev;
>  
> -- 
> 2.24.1
> 
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

  parent reply	other threads:[~2020-01-23 17:18 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23 12:04 [PATCH] bpf: devmap: Pass lockdep expression to RCU lists Amol Grover
2020-01-23 12:04 ` [Linux-kernel-mentees] " Amol Grover
2020-01-23 13:37 ` Jesper Dangaard Brouer
2020-01-23 13:37   ` [Linux-kernel-mentees] " Jesper Dangaard Brouer
2020-01-23 13:42   ` Toke Høiland-Jørgensen
2020-01-23 13:42     ` [Linux-kernel-mentees] " Toke Høiland-Jørgensen
2020-01-23 17:10     ` Amol Grover
2020-01-23 17:10       ` [Linux-kernel-mentees] " Amol Grover
2020-01-23 13:38 ` Toke Høiland-Jørgensen
2020-01-23 13:38   ` [Linux-kernel-mentees] " Toke Høiland-Jørgensen
2020-01-23 15:59   ` Daniel Borkmann
2020-01-23 15:59     ` [Linux-kernel-mentees] " Daniel Borkmann
2020-01-23 17:18 ` Amol Grover [this message]
2020-01-23 17:18   ` Amol Grover
2020-01-23 22:04   ` Daniel Borkmann
2020-01-23 22:04     ` [Linux-kernel-mentees] " Daniel Borkmann

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