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[146.241.243.102]) by smtp.gmail.com with ESMTPSA id y21-20020a17090629d500b00a1d3b1c311csm1260323eje.164.2023.12.06.02.58.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Dec 2023 02:58:34 -0800 (PST) Message-ID: Subject: Re: [net-next PATCH v6 1/2] octeontx2-af: Add new mbox to support multicast/mirror offload From: Paolo Abeni To: Suman Ghosh , sgoutham@marvell.com, gakula@marvell.com, sbhatta@marvell.com, hkelam@marvell.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, lcherian@marvell.com, jerinj@marvell.com, horms@kernel.org, wojciech.drewek@intel.com Date: Wed, 06 Dec 2023 11:58:32 +0100 In-Reply-To: <20231204141956.3956942-2-sumang@marvell.com> References: <20231204141956.3956942-1-sumang@marvell.com> <20231204141956.3956942-2-sumang@marvell.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2023-12-04 at 19:49 +0530, Suman Ghosh wrote: > A new mailbox is added to support offloading of multicast/mirror > functionality. The mailbox also supports dynamic updation of the > multicast/mirror list. >=20 > Signed-off-by: Suman Ghosh > Reviewed-by: Wojciech Drewek > Reviewed-by: Simon Horman Note that v5 was already applied to net-next. But I still have a relevant note, see below. > @@ -5797,3 +6127,337 @@ int rvu_mbox_handler_nix_bandprof_get_hwinfo(stru= ct rvu *rvu, struct msg_req *re > =20 > return 0; > } > + > +static struct nix_mcast_grp_elem *rvu_nix_mcast_find_grp_elem(struct nix= _mcast_grp *mcast_grp, > + u32 mcast_grp_idx) > +{ > + struct nix_mcast_grp_elem *iter; > + bool is_found =3D false; > + > + mutex_lock(&mcast_grp->mcast_grp_lock); > + list_for_each_entry(iter, &mcast_grp->mcast_grp_head, list) { > + if (iter->mcast_grp_idx =3D=3D mcast_grp_idx) { > + is_found =3D true; > + break; > + } > + } > + mutex_unlock(&mcast_grp->mcast_grp_lock); AFAICS, at this point another thread/CPU could kick-in and run rvu_mbox_handler_nix_mcast_grp_destroy() up to completion, freeing 'iter' before it's later used by the current thread. What prevents such scenario? _If_ every mcast group manipulation happens under the rtnl lock, then you could as well completely remove the confusing mcast_grp_lock. Cheers, Paolo