From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: paulmck@kernel•org
Cc: bpf@vger•kernel.org, netdev@vger•kernel.org,
Martin KaFai Lau <kafai@fb•com>,
Hangbin Liu <liuhangbin@gmail•com>,
Jesper Dangaard Brouer <brouer@redhat•com>,
Magnus Karlsson <magnus.karlsson@gmail•com>,
Michael Chan <michael.chan@broadcom•com>
Subject: Re: [PATCH bpf-next 06/17] bnxt: remove rcu_read_lock() around XDP program invocation
Date: Thu, 10 Jun 2021 10:47:00 +0200 [thread overview]
Message-ID: <87eedam7i3.fsf@toke.dk> (raw)
In-Reply-To: <20210609135834.GC4397@paulmck-ThinkPad-P17-Gen-1>
"Paul E. McKenney" <paulmck@kernel•org> writes:
> On Wed, Jun 09, 2021 at 12:33:15PM +0200, Toke Høiland-Jørgensen wrote:
>> The bnxt driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP
>> program invocations. However, the actual lifetime of the objects referred
>> by the XDP program invocation is longer, all the way through to the call to
>> xdp_do_flush(), making the scope of the rcu_read_lock() too small. This
>> turns out to be harmless because it all happens in a single NAPI poll
>> cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock()
>> misleading.
>>
>> Rather than extend the scope of the rcu_read_lock(), just get rid of it
>> entirely. With the addition of RCU annotations to the XDP_REDIRECT map
>> types that take bh execution into account, lockdep even understands this to
>> be safe, so there's really no reason to keep it around.
>
> And same for the rest of these removals. Someone might be very happy
> to have that comment at some later date, and that someone just might
> be you. ;-)
Bah, why do you have to go and make sensible suggestions like that? ;)
Will wait for Martin's review and add this in a v2. BTW, is it OK to
include your patch in the series like this, or should I rather request
that your tree be merged into bpf-next?
-Toke
next prev parent reply other threads:[~2021-06-10 8:47 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 10:33 [PATCH bpf-next 00/17] Clean up and document RCU-based object protection for XDP_REDIRECT Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 01/17] rcu: Create an unrcu_pointer() to remove __rcu from a pointer Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 02/17] bpf: allow RCU-protected lookups to happen from bh context Toke Høiland-Jørgensen
2021-06-10 18:38 ` Alexei Starovoitov
2021-06-10 21:24 ` Daniel Borkmann
2021-06-10 22:27 ` Toke Høiland-Jørgensen
2021-06-10 19:33 ` Martin KaFai Lau
2021-06-09 10:33 ` [PATCH bpf-next 03/17] dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU dev ref Toke Høiland-Jørgensen
2021-06-10 19:37 ` Martin KaFai Lau
2021-06-10 23:05 ` Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 04/17] xdp: add proper __rcu annotations to redirect map entries Toke Høiland-Jørgensen
2021-06-10 21:09 ` Martin KaFai Lau
2021-06-10 23:19 ` Toke Høiland-Jørgensen
2021-06-10 23:32 ` Martin KaFai Lau
2021-06-10 23:41 ` Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 05/17] ena: remove rcu_read_lock() around XDP program invocation Toke Høiland-Jørgensen
2021-06-09 13:57 ` Paul E. McKenney
2021-06-09 10:33 ` [PATCH bpf-next 06/17] bnxt: " Toke Høiland-Jørgensen
2021-06-09 13:58 ` Paul E. McKenney
2021-06-10 8:47 ` Toke Høiland-Jørgensen [this message]
2021-06-09 10:33 ` [PATCH bpf-next 07/17] thunderx: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 08/17] freescale: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 09/17] net: intel: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 10/17] marvell: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 11/17] mlx4: " Toke Høiland-Jørgensen
2021-06-10 7:10 ` Tariq Toukan
2021-06-09 10:33 ` [PATCH bpf-next 12/17] nfp: " Toke Høiland-Jørgensen
2021-06-11 16:30 ` Simon Horman
2021-06-09 10:33 ` [PATCH bpf-next 13/17] qede: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 14/17] sfc: " Toke Høiland-Jørgensen
2021-06-09 12:15 ` Edward Cree
2021-06-09 10:33 ` [PATCH bpf-next 15/17] netsec: " Toke Høiland-Jørgensen
2021-06-10 5:30 ` Ilias Apalodimas
2021-06-09 10:33 ` [PATCH bpf-next 16/17] stmmac: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 17/17] net: ti: " Toke Høiland-Jørgensen
2021-06-09 17:04 ` Grygorii Strashko
2021-06-10 0:18 ` [PATCH bpf-next 00/17] Clean up and document RCU-based object protection for XDP_REDIRECT Yonghong Song
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