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Fri, 26 Jul 2019 16:20:08 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 3FDB32022974A; Fri, 26 Jul 2019 18:20:05 +0200 (CEST) Message-Id: <20190726161357.397880775@infradead.org> User-Agent: quilt/0.65 Date: Fri, 26 Jul 2019 16:54:10 +0200 From: Peter Zijlstra To: mingo@kernel.org, juri.lelli@redhat.com Cc: linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, luca.abeni@santannapisa.it, bristot@redhat.com, balsini@android.com, dvyukov@google.com, tglx@linutronix.de, vpillai@digitalocean.com, rostedt@goodmis.org, peterz@infradead.org Subject: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period References: <20190726145409.947503076@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Cc: Daniel Bristot de Oliveira Cc: Luca Abeni Cc: Juri Lelli Cc: Dmitry Vyukov Signed-off-by: Peter Zijlstra (Intel) --- include/linux/sched/sysctl.h | 3 +++ kernel/sched/deadline.c | 23 +++++++++++++++++++++-- kernel/sysctl.c | 14 ++++++++++++++ 3 files changed, 38 insertions(+), 2 deletions(-) --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -56,6 +56,9 @@ int sched_proc_update_handler(struct ctl extern unsigned int sysctl_sched_rt_period; extern int sysctl_sched_rt_runtime; +extern unsigned int sysctl_sched_dl_period_max; +extern unsigned int sysctl_sched_dl_period_min; + #ifdef CONFIG_UCLAMP_TASK extern unsigned int sysctl_sched_uclamp_util_min; extern unsigned int sysctl_sched_uclamp_util_max; --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2597,6 +2597,14 @@ void __getparam_dl(struct task_struct *p } /* + * Default limits for DL period; on the top end we guard against small util + * tasks still getting rediculous long effective runtimes, on the bottom end we + * guard against timer DoS. + */ +unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */ +unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */ + +/* * This function validates the new parameters of a -deadline task. * We ask for the deadline not being zero, and greater or equal * than the runtime, as well as the period of being zero or @@ -2608,6 +2616,8 @@ void __getparam_dl(struct task_struct *p */ bool __checkparam_dl(const struct sched_attr *attr) { + u64 period, max, min; + /* special dl tasks don't actually use any parameter */ if (attr->sched_flags & SCHED_FLAG_SUGOV) return true; @@ -2631,12 +2641,21 @@ bool __checkparam_dl(const struct sched_ attr->sched_period & (1ULL << 63)) return false; + period = attr->sched_period; + if (!period) + period = attr->sched_deadline; + /* runtime <= deadline <= period (if period != 0) */ - if ((attr->sched_period != 0 && - attr->sched_period < attr->sched_deadline) || + if (period < attr->sched_deadline || attr->sched_deadline < attr->sched_runtime) return false; + max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC; + min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC; + + if (period < min || period > max) + return false; + return true; } --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -443,6 +443,20 @@ static struct ctl_table kern_table[] = { .proc_handler = sched_rt_handler, }, { + .procname = "sched_deadline_period_max_us", + .data = &sysctl_sched_dl_period_max, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, + { + .procname = "sched_deadline_period_min_us", + .data = &sysctl_sched_dl_period_min, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, + { .procname = "sched_rr_timeslice_ms", .data = &sysctl_sched_rr_timeslice, .maxlen = sizeof(int),