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McKenney" , linux-mm@kvack.org Date: Tue, 25 Feb 2025 08:05:08 +0100 In-Reply-To: <2bc76f69-901c-4d2c-bd75-64e757ec2230@efficios.com> References: <20250224132836.383041-1-gmonaco@redhat.com> <20250224132836.383041-3-gmonaco@redhat.com> <2bc76f69-901c-4d2c-bd75-64e757ec2230@efficios.com> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: HelEcE0ua68Hs2IFW4-fk8btovADzHo4aNenEWilLDc_1740467113 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 79CBD180009 X-Stat-Signature: m4f7f9ubsbjg1qhw8ny9o1s8kdoe7qzo X-Rspam-User: X-HE-Tag: 1740467121-712520 X-HE-Meta: U2FsdGVkX1+OJs45NReQkNrBj0LYKHe9TIewqnxUYSeWLpLOA9g9kKSRQJrIGRC3ODCWCUf3j6KHvv2PRAg7rK1LIjvhE/0ZNiIXHBM12aH1QJrzb2l1hVxWHUCU9gYTBjuD5+uJl4vl2kC6sxL7zsgooN5MrOYWUwOYjIZZhKY3VOVs2MQt0eH4jmAZAFs9kgwOPrjtbo8tDGOutWJaOe0dLT5a8yMXhZHgGS+xfdMAmd+g1ZgyOTkrjpQXaJlrDhH3c9ebPJat/MEXunmJP1OEBQVwAG9J8SZuXNH2AgCklfewrUnmooySN3RPVVHL47h+1XBDdmkOfE7Nv1Ro3CEaAO6qvYNAjlWlvCwe/21AeIHNGNrzHzTUvksw5+ydyg6jXeoHha28NOsZy+2MuJwbaygz/34Or74xjo+4TxZZK5XO2MpqZxI4wqlLilpbuDAs5YdR5FDW4w3DFpBEFffcYlQh7JapnGtc5m7PrkAEZtBfM9cdtrqoS8iyrUfbaiRoUbj89rrUELWyzzbX7SNIpH19Wi7dt0i2fB3W6AZ+JxjA+RoI2GOYPVcBMFIgnICZGoaHIsLpUS55bqIQTnT/k90qMZxZYzPOA1TPzzPnzTNekcfskrlVa2F+QnGi4KyGVHgc55CJVCerUTLABj2joc1rww1HmfTP7M+9Ts/+eMrMYC6jUBuuOUMVlMWV12jH7nmH54YbMRls8D8p2umOZ8ZkjeeZaojNZF9j6+JJc3whPJYVKY8fRp+DTlSJWc1UIv9iZcxD4vfvLHJU+OJiOwTgynXyb+8ghLM448V+34T/WRgl9V9S1h1m9qrjeYP04wov1WF0AfarJQt272aNtzqqh8NcgGAb9gGdPO6PccO3VnF5drZFyDNojBHcoe6cA5i5CT3W5GkF5IugeMmaWm1vss1dycf4+Wo1Fri3zMSj8ZUA+NPkkPAAjU3rkZZWASWZQrtd1yRyv8m McUYDqcu MnDbCh9TwsIR29u9ZmC9Bet97JyU4S1DzwXtdHvyRzPub8jvj61r4AZXiAiz6nvn05mN/KELWoB35FLfhT0N3CBcVXNCJEXJcnM3X549lpMmUdkVlHKpk9JtPd21IysWDxUM8yQ1sEXTHGnnzJvrI5jjmidEpMzGOHMrBFaRrC9HKZmLSuDBMPdCrxwVS1JxDOxmy2CdkmuzzmjcLAZ+frz8RbMb04ZtM5LjxyolmvgynI6ILs8dWvXJmg0dUmF7IN2tNV2R204cbVDkIRX6eUvY4jq/TjjE3x/D2U/ngQXcnuGdntVDPdZJC21HDVOX3qmg5kAab2bAUvfSa0/nfiZM5x2cCWINDS3x0JI1Cdd0W2ekLeQySCdNFZUM7kIO8Nhm/ 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 Mon, 2025-02-24 at 15:50 -0500, Mathieu Desnoyers wrote: > On 2025-02-24 08:28, Gabriele Monaco wrote: > [...] > > diff --git a/kernel/rseq.c b/kernel/rseq.c > > index 2cb16091ec0ae..936863fe7eb37 100644 > > --- a/kernel/rseq.c > > +++ b/kernel/rseq.c > > @@ -419,6 +419,7 @@ void __rseq_handle_notify_resume(struct ksignal > > *ksig, struct pt_regs *regs) > > =C2=A0=C2=A0=09} > > =C2=A0=C2=A0=09if (unlikely(rseq_update_cpu_node_id(t))) > > =C2=A0=C2=A0=09=09goto error; > > +=09task_queue_mm_cid(t); >=20 > Given that task_queue_mm_cid() will be called quite frequently from > __rseq_handle_notify_resume, perhaps it would be best to move at > least > the portion responsible for checks (including the time_before()) to > include/linux/sched.h to eliminate a function call from the fast > path. >=20 >=20 Right, good idea. Thinking about that, task_queue_mm_cid checks a bit more than the __rseq_handle_notify_resume. As far as I understand, as long as we only call task_queue_mm_cid from __rseq_handle_notify_resume, it won't ever be called from a kthread (I assume the t->rseq implies t->mm and not PF_KTHREAD but also by construction since it's called in return to user). In short, considering we already check for PF_EXITING, the following is just superfluous: if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD))) =09return; and we could just keep the time_before check in __rseq_handle_notify_resume, perhaps adding a t->mm check just to avoid a perceived NULL pointer dereference, which seems not possible anyway. Am I missing any corner case? Thanks, Gabriele