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AJvYcCVt8nPIIQtYlpjBLC+2fA72wHUHteKodr/GDf1D+TLLt1TDUDoZTVW+7aQeDVBRnOzPlZbOhOsAt5jHrfs=@vger.kernel.org X-Gm-Message-State: AOJu0YyM7lrqsSB/d0Cs+WmP2JAWJwXpVUzBIhStmHEJlWlqWfDwxNgO OipfXPHYbl19156WnI81Lz+rtRaeQ8375MSuLkvIHeun8jUwNeF8qt+rBio2p+Ik58BZt2lpj3u It/BvbGDKqCLtT8iww5PYnDcYRCHGCmjfmgR+B0Q= X-Gm-Gg: AZuq6aJsy//GxBlJg3BwWG7ZXE35ul+XwRaPoibrFNk9dcKCj+OOjLMD2BeK1NoNJPd GGLv1HB7JxDx7M/eoMhZBVRdc2JegLWaxm4oiri9eg1k1YV5qX/xNl1Bv8qTf7RvJtsKEyZZj5U AtioEX6lc1i2u6VgdKd+YZZCuq3zmF3dzeLq+XjDsdWuSLCdGLhoiilngfAif6LJfT7MPIKo+p+ 9WtUypaNRHl71v77PdGUA+DbChYvJoT86thCQ3jVsAOlRnThKLfKoi7lYpAxJDFDy7dO8Coiugh ApH3jLv/tCjBVk8FKu6sZVIC+dsymw== X-Received: by 2002:a4a:e049:0:b0:66b:8c7f:6c2 with SMTP id 006d021491bc7-66b8c7f0d72mr913651eaf.57.1770269585603; Wed, 04 Feb 2026 21:33:05 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260203171305.95085-1-mmyangfl@gmail.com> <20260203171305.95085-4-mmyangfl@gmail.com> <20260204211252.71b8fa86@kernel.org> In-Reply-To: <20260204211252.71b8fa86@kernel.org> From: David Yang Date: Thu, 5 Feb 2026 13:32:29 +0800 X-Gm-Features: AZwV_QiSboIcl_zN0LI4N_HOcELIAh6t0pprNBheKTrw2yOY6Udm5qDHbkSmF94 Message-ID: Subject: Re: [PATCH net-next 3/3] net: dsa: yt921x: Use u64_stats_t for MIB stats To: Jakub Kicinski Cc: netdev@vger.kernel.org, Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Paolo Abeni , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, Feb 5, 2026 at 1:12=E2=80=AFPM Jakub Kicinski wro= te: > > On Wed, 4 Feb 2026 01:12:43 +0800 David Yang wrote: > > 64-bit variables might not be atomic on 32-bit architectures, thus > > cannot be unconditionally made lock-free. Use u64_stats_t so it would > > still be lock-free on 64-bit architectures. > > IDK why we need to worry about lock free reading of those 64b values... > > > @@ -771,22 +785,27 @@ yt921x_dsa_get_ethtool_stats(struct dsa_switch *d= s, int port, uint64_t *data) > > struct yt921x_priv *priv =3D to_yt921x_priv(ds); > > struct yt921x_port *pp =3D &priv->ports[port]; > > struct yt921x_mib *mib =3D &pp->mib; > > + unsigned int start; > > size_t j; > > > > mutex_lock(&priv->reg_lock); > > yt921x_read_mib(priv, port); > > mutex_unlock(&priv->reg_lock); > > ..when in all(?) the readers converted by this patch we take the mutex > to refresh the stats anyway. And presumably do expensive IO/reg reads > under that mutex. So just extend the mutex over the read section and > save us the retry logic, please, it will make no difference to perf. .get_stats64() is atomic, that's why everyone (mostly) is using u64_stats_t for DSA stats.