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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>,
	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 14:42:03 +0100	[thread overview]
Message-ID: <87a76e9tn8.fsf@toke.dk> (raw)
In-Reply-To: <20200123143725.036140e7@carbon>

Jesper Dangaard Brouer <brouer@redhat.com> writes:

> 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?

I concluded 'yes' from the comment on hlist_for_each_entry_rcu():

The lockdep condition gets passed to this:

#define __list_check_rcu(dummy, cond, extra...)				\
	({								\
	check_arg_count_one(extra);					\
	RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(),		\
			 "RCU-list traversed in non-reader section!");	\
	 })


so that seems fine :)

-Toke


WARNING: multiple messages have this Message-ID (diff)
From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>,
	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 14:42:03 +0100	[thread overview]
Message-ID: <87a76e9tn8.fsf@toke.dk> (raw)
In-Reply-To: <20200123143725.036140e7@carbon>

Jesper Dangaard Brouer <brouer@redhat.com> writes:

> 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?

I concluded 'yes' from the comment on hlist_for_each_entry_rcu():

The lockdep condition gets passed to this:

#define __list_check_rcu(dummy, cond, extra...)				\
	({								\
	check_arg_count_one(extra);					\
	RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(),		\
			 "RCU-list traversed in non-reader section!");	\
	 })


so that seems fine :)

-Toke

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Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
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  reply	other threads:[~2020-01-23 13:42 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 [this message]
2020-01-23 13:42     ` 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

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