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McKenney" , b.a.t.m.a.n@lists.open-mesh.org Cc: b.a.t.m.a.n@lists.open-mesh.org, Dmitry Antipov , netdev@vger.kernel.org, rcu@vger.kernel.org, Linus =?ISO-8859-1?Q?L=FCssing?= Subject: Re: [PATCH] Revert "batman-adv: prefer kfree_rcu() over call_rcu() with free-only callbacks" Date: Wed, 12 Jun 2024 20:22:49 +0200 Message-ID: <2328482.ElGaqSPkdT@sven-l14> In-Reply-To: References: <20240612133357.2596-1-linus.luessing@c0d3.blue> <020489fa-26a3-422c-8924-7dc71f23422c@paulmck-laptop> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart4898629.GXAFRqVoOG"; micalg="pgp-sha512"; protocol="application/pgp-signature" Message-ID-Hash: 6YCHHJOXAI22GOAO7I2RF6CY42GWHIEY X-Message-ID-Hash: 6YCHHJOXAI22GOAO7I2RF6CY42GWHIEY X-MailFrom: sven@narfation.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-b.a.t.m.a.n.lists.open-mesh.org-0; header-match-b.a.t.m.a.n.lists.open-mesh.org-1; header-match-b.a.t.m.a.n.lists.open-mesh.org-2; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: The list for a Better Approach To Mobile Ad-hoc Networking Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --nextPart4898629.GXAFRqVoOG Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1"; protected-headers="v1" From: Sven Eckelmann Date: Wed, 12 Jun 2024 20:22:49 +0200 Message-ID: <2328482.ElGaqSPkdT@sven-l14> In-Reply-To: MIME-Version: 1.0 On Wednesday, 12 June 2024 18:31:57 CEST Linus L=FCssing wrote: > On Wed, Jun 12, 2024 at 09:06:25AM -0700, Paul E. McKenney wrote: > > We are looking into nice ways of solving this, but in the meantime, > > yes, if you are RCU-freeing slab objects into a slab that is destroyed > > at module-unload time, you currently need to stick with call_rcu() > > and rcu_barrier(). > > > > We do have some potential solutions to allow use of kfree_rcu() with > > this sort of slab, but they are still strictly potential. > > > > Apologies for my having failed to foresee this particular trap! >=20 > No worries, thanks for the help and clarification! This at least > restored my sanity, was starting to doubt my understanding of RCU > and the batman-adv code the longer I tried to find the issue in > batman-adv :D. Thanks Linus and Paul. I've queued up the revert. But feel free to submit a= =20 version with updated text in case you want to incorporate information from= =20 this thread. Kind regards, Sven --nextPart4898629.GXAFRqVoOG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQS81G/PswftH/OW8cVND3cr0xT1ywUCZmnnegAKCRBND3cr0xT1 y/2ZAQCJLtdWIbCPUrkTqkI9mv1ThzM/ZcLceVmbFSKhVCSe8AEAtVQx2GE9aUCk S1OPFkU0m5zCxxMHHIygDnw3SwaMvAA= =mD28 -----END PGP SIGNATURE----- --nextPart4898629.GXAFRqVoOG--