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Mon, 02 Mar 2026 06:37:51 -0800 (PST) X-Received: by 2002:a05:600c:3486:b0:480:3a72:524a with SMTP id 5b1f17b1804b1-483c9bed89emr249011255e9.19.1772462271471; Mon, 02 Mar 2026 06:37:51 -0800 (PST) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.73.19]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483bd70e6c9sm361018285e9.8.2026.03.02.06.37.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Mar 2026 06:37:50 -0800 (PST) Date: Mon, 2 Mar 2026 15:37:48 +0100 From: Juri Lelli To: Gabriele Monaco Cc: linux-kernel@vger.kernel.org, Steven Rostedt , Nam Cao , Juri Lelli , Jonathan Corbet , Masami Hiramatsu , linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra , Tomas Glozar , Clark Williams , John Kacur Subject: Re: [PATCH v6 15/16] rv: Add deadline monitors Message-ID: References: <20260225095122.80683-1-gmonaco@redhat.com> <20260225095122.80683-16-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260225095122.80683-16-gmonaco@redhat.com> Hello, On 25/02/26 10:51, Gabriele Monaco wrote: > Add the deadline monitors collection to validate the deadline scheduler, > both for deadline tasks and servers. > > The currently implemented monitors are: > * throttle: > validate dl entities are throttled when they use up their runtime > * nomiss: > validate dl entities run to completion before their deadiline > > Cc: Peter Zijlstra > Reviewed-by: Nam Cao > Signed-off-by: Gabriele Monaco > --- ... > +static inline int extract_params(struct pt_regs *regs, long id, struct task_struct **p) > +{ > + size_t size = offsetof(struct sched_attr, sched_nice); > + struct sched_attr __user *uattr, attr; > + int new_policy = -1, ret; > + unsigned long args[6]; > + pid_t pid; > + > + switch (id) { > + case __NR_sched_setscheduler: > + syscall_get_arguments(current, regs, args); > + pid = args[0]; > + new_policy = args[1]; > + break; > + case __NR_sched_setattr: > + syscall_get_arguments(current, regs, args); > + pid = args[0]; > + uattr = (void *)args[1]; > + /* > + * Just copy up to sched_flags, we are not interested after that > + */ > + ret = copy_struct_from_user(&attr, size, uattr, size); > + if (ret) > + return ret; > + if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY) > + return -EINVAL; > + new_policy = attr.sched_policy; > + break; > + default: > + return -EINVAL; > + } > + if (!pid) > + *p = current; > + else { > + /* > + * Required for find_task_by_vpid, make sure the caller doesn't > + * need to get_task_struct(). > + */ > + guard(rcu)(); > + *p = find_task_by_vpid(pid); > + if (unlikely(!*p)) > + return -EINVAL; > + } Not sure I get this comment. RCU is released when the function returns, but then the task pointer is dereferenced by callers? Thanks, Juri