All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Amol Grover <frextrite@gmail.com>
Cc: brouer@redhat.com, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	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>,
	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 14:37:25 +0100	[thread overview]
Message-ID: <20200123143725.036140e7@carbon> (raw)
In-Reply-To: <20200123120437.26506-1-frextrite@gmail.com>

On Thu, 23 Jan 2020 17:34:38 +0530
Amol Grover <frextrite@gmail.com> 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.

We do hold the lock in update and delete cases, but not in the lookup
cases.  Is it then still okay to add the lockdep_is_held() annotation?

If it is then it looks fine to me:

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
 
> Hence, add corresponding lockdep expression to silence false-positive
> lockdep warnings, and harden RCU lists.
> 
> 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;
>  

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer


WARNING: multiple messages have this Message-ID (diff)
From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Amol Grover <frextrite@gmail.com>
Cc: Song Liu <songliubraving@fb.com>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	netdev@vger.kernel.org, John Fastabend <john.fastabend@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>,
	brouer@redhat.com, Joel Fernandes <joel@joelfernandes.org>,
	Yonghong Song <yhs@fb.com>,
	bpf@vger.kernel.org, Andrii Nakryiko <andriin@fb.com>,
	"David S . Miller" <davem@davemloft.net>,
	linux-kernel@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 14:37:25 +0100	[thread overview]
Message-ID: <20200123143725.036140e7@carbon> (raw)
In-Reply-To: <20200123120437.26506-1-frextrite@gmail.com>

On Thu, 23 Jan 2020 17:34:38 +0530
Amol Grover <frextrite@gmail.com> 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.

We do hold the lock in update and delete cases, but not in the lookup
cases.  Is it then still okay to add the lockdep_is_held() annotation?

If it is then it looks fine to me:

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
 
> Hence, add corresponding lockdep expression to silence false-positive
> lockdep warnings, and harden RCU lists.
> 
> 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;
>  

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

  reply	other threads:[~2020-01-23 13:37 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 [this message]
2020-01-23 13:37   ` 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
2020-01-23 17:18   ` [Linux-kernel-mentees] " Amol Grover
2020-01-23 22:04   ` Daniel Borkmann
2020-01-23 22:04     ` [Linux-kernel-mentees] " Daniel Borkmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200123143725.036140e7@carbon \
    --to=brouer@redhat.com \
    --cc=andriin@fb.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=frextrite@gmail.com \
    --cc=hawk@kernel.org \
    --cc=jakub.kicinski@netronome.com \
    --cc=joel@joelfernandes.org \
    --cc=john.fastabend@gmail.com \
    --cc=kafai@fb.com \
    --cc=linux-kernel-mentees@lists.linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=madhuparnabhowmik04@gmail.com \
    --cc=netdev@vger.kernel.org \
    --cc=paulmck@kernel.org \
    --cc=songliubraving@fb.com \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.