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McKenney" , Vlastimil Babka , Marco Elver , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, sfr@canb.auug.org.au, longman@redhat.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, Tomas Gleixner , Peter Zijlstra Subject: Re: [PATCH 2/2] scftorture: Use a lock-less list to free memory. Message-ID: <20241107112107.3rO2RTzX@linutronix.de> References: <88694240-1eea-4f4c-bb7b-80de25f252e7@paulmck-laptop> <20241104105053.2182833-1-bigeasy@linutronix.de> <20241104105053.2182833-2-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B55D0C000A X-Stat-Signature: jdf16ar8kbw55dmsfrcap6m8tqdi44hg X-Rspam-User: X-HE-Tag: 1730978433-754564 X-HE-Meta: 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 ul7VNKyX lsiYH4tOg12SFbDoiIXgn+fEM5Irovx22ga81m004E8fgWS54N4biseDs3HkNlpoob16u9dF72U0dBafnA0p858EjzJwVTr8qJIzGVZeKtrJNqptRvK5G04V9SGsNCkek1FdpgS4dgCiyu4M+1lc2gDl8BCq8GiIIDgMCzrV4cGFbbRqToU5n5NRmcXND+5XfB1qeVBSayx6V28R3taFoqa+zUz6jWAkaHlQVnuK0JADIx+NpyPGn8UM9oPIzaHFBFsH1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024-11-04 17:00:19 [-0800], Boqun Feng wrote: > Hi Sebastian, Hi Boqun, =E2=80=A6 > I think this needs to be: >=20 > scf_cleanup_free_list(cpu); >=20 > or >=20 > scf_cleanup_free_list(curcpu); >=20 > because scfp->cpu is actually the thread number, and I got a NULL > dereference: >=20 > [ 14.219225] BUG: unable to handle page fault for address: ffffffffb2ff= 7210 Right. Replaced with cpu. =E2=80=A6 >=20 > Another thing is, how do we guarantee that we don't exit the loop > eariler (i.e. while there are still callbacks on the list)? After the > following scftorture_invoke_one(), there could an IPI pending somewhere, > and we may exit this loop if torture_must_stop() is true. And that IPI > might add its scf_check to the list but no scf_cleanup_free_list() is > going to handle that, right? Okay. Assuming that IPIs are done by the time scf_torture_cleanup is invoked, I added scf_cleanup_free_list() for all CPUs there. Reposted at https://lore.kernel.org/20241107111821.3417762-1-bigeasy@linutronix.de > Regards, > Boqun Sebastian