From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F155AC55ABD for ; Thu, 5 Nov 2020 23:48:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA0F120756 for ; Thu, 5 Nov 2020 23:48:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604620117; bh=MU6emrq29RkuU/tk4hK16G6QfDH70QVRiaNynIsxyoY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gKns5JCFnbtrMN0I0JqtzyeRLEuBpiaBkIk6NbghG8Kx9vhWsW6ocX/mMMK0ytEpd OaaYQ94G2IBO5kWjwenniK/StGUllcUb9Mbc4rGlkFGmb/W5lvb8E/Nl0qerq4CwQw h7NusxWr+YyE8y6huNm2myUqsUOZo08c4Lt1wKLQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733072AbgKEXsg (ORCPT ); Thu, 5 Nov 2020 18:48:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:46182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732754AbgKEXr3 (ORCPT ); Thu, 5 Nov 2020 18:47:29 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5FF1F22228; Thu, 5 Nov 2020 23:47:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604620048; bh=MU6emrq29RkuU/tk4hK16G6QfDH70QVRiaNynIsxyoY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jxQ91eNrAeMGGy++7GbW3ZnI9/G5THaOJx3rsivPl5Yyr0CenuOUSmMB4ohXOI2Rz JdqVSn5Nd7l1lmn1Xp9lWAeMCp4nvQYCIuNBpMpYtIzlG3JRGFywiIE1Xca1FrflJP e3r0xIkuq5SMmpV1LSpByCJVnMAUy0QEs1n2Ow0o= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 18/28] rcutorture: Make stutter_wait() caller restore priority Date: Thu, 5 Nov 2020 15:47:09 -0800 Message-Id: <20201105234719.23307-18-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20201105234658.GA23142@paulmck-ThinkPad-P72> References: <20201105234658.GA23142@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Currently, stutter_wait() will happily spin waiting for the stutter interval to end even if the caller is running at a real-time priority level. This could starve normal-priority tasks for no good reason. This commit therefore drops the calling task's priority to SCHED_OTHER MAX_NICE if stutter_wait() needs to wait. But when it waits, stutter_wait() returns true, which allows the caller to restore the priority if needed. Callers that were already running at SCHED_OTHER MAX_NICE obviously do not need any changes, but this commit also restores priority for higher-priority callers. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 24 ++++++++++++++++++------ kernel/torture.c | 9 ++++----- 2 files changed, 22 insertions(+), 11 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index db37671..4391d2f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -912,7 +912,8 @@ static int rcu_torture_boost(void *arg) oldstarttime = boost_starttime; while (time_before(jiffies, oldstarttime)) { schedule_timeout_interruptible(oldstarttime - jiffies); - stutter_wait("rcu_torture_boost"); + if (stutter_wait("rcu_torture_boost")) + sched_set_fifo_low(current); if (torture_must_stop()) goto checkwait; } @@ -932,7 +933,8 @@ static int rcu_torture_boost(void *arg) jiffies); call_rcu_time = jiffies; } - stutter_wait("rcu_torture_boost"); + if (stutter_wait("rcu_torture_boost")) + sched_set_fifo_low(current); if (torture_must_stop()) goto checkwait; } @@ -964,7 +966,8 @@ static int rcu_torture_boost(void *arg) } /* Go do the stutter. */ -checkwait: stutter_wait("rcu_torture_boost"); +checkwait: if (stutter_wait("rcu_torture_boost")) + sched_set_fifo_low(current); } while (!torture_must_stop()); /* Clean up and exit. */ @@ -987,6 +990,7 @@ rcu_torture_fqs(void *arg) { unsigned long fqs_resume_time; int fqs_burst_remaining; + int oldnice = task_nice(current); VERBOSE_TOROUT_STRING("rcu_torture_fqs task started"); do { @@ -1002,7 +1006,8 @@ rcu_torture_fqs(void *arg) udelay(fqs_holdoff); fqs_burst_remaining -= fqs_holdoff; } - stutter_wait("rcu_torture_fqs"); + if (stutter_wait("rcu_torture_fqs")) + sched_set_normal(current, oldnice); } while (!torture_must_stop()); torture_kthread_stopping("rcu_torture_fqs"); return 0; @@ -1022,9 +1027,11 @@ rcu_torture_writer(void *arg) bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal; bool gp_sync1 = gp_sync; int i; + int oldnice = task_nice(current); struct rcu_torture *rp; struct rcu_torture *old_rp; static DEFINE_TORTURE_RANDOM(rand); + bool stutter_waited; int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC, RTWS_COND_GET, RTWS_SYNC }; int nsynctypes = 0; @@ -1143,7 +1150,8 @@ rcu_torture_writer(void *arg) !rcu_gp_is_normal(); } rcu_torture_writer_state = RTWS_STUTTER; - if (stutter_wait("rcu_torture_writer") && + stutter_waited = stutter_wait("rcu_torture_writer"); + if (stutter_waited && !READ_ONCE(rcu_fwd_cb_nodelay) && !cur_ops->slow_gps && !torture_must_stop() && @@ -1155,6 +1163,8 @@ rcu_torture_writer(void *arg) rcu_ftrace_dump(DUMP_ALL); WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count); } + if (stutter_waited) + sched_set_normal(current, oldnice); } while (!torture_must_stop()); rcu_torture_current = NULL; // Let stats task know that we are done. /* Reset expediting back to unexpedited. */ @@ -2103,6 +2113,7 @@ static struct notifier_block rcutorture_oom_nb = { /* Carry out grace-period forward-progress testing. */ static int rcu_torture_fwd_prog(void *args) { + int oldnice = task_nice(current); struct rcu_fwd *rfp = args; int tested = 0; int tested_tries = 0; @@ -2121,7 +2132,8 @@ static int rcu_torture_fwd_prog(void *args) rcu_torture_fwd_prog_cr(rfp); /* Avoid slow periods, better to test when busy. */ - stutter_wait("rcu_torture_fwd_prog"); + if (stutter_wait("rcu_torture_fwd_prog")) + sched_set_normal(current, oldnice); } while (!torture_must_stop()); /* Short runs might not contain a valid forward-progress attempt. */ WARN_ON(!tested && tested_tries >= 5); diff --git a/kernel/torture.c b/kernel/torture.c index d8bdd9a..8995ed1 100644 --- a/kernel/torture.c +++ b/kernel/torture.c @@ -604,19 +604,19 @@ bool stutter_wait(const char *title) { ktime_t delay; unsigned i = 0; - int oldnice; bool ret = false; int spt; cond_resched_tasks_rcu_qs(); spt = READ_ONCE(stutter_pause_test); for (; spt; spt = READ_ONCE(stutter_pause_test)) { - ret = true; + if (!ret) { + sched_set_normal(current, MAX_NICE); + ret = true; + } if (spt == 1) { schedule_timeout_interruptible(1); } else if (spt == 2) { - oldnice = task_nice(current); - set_user_nice(current, MAX_NICE); while (READ_ONCE(stutter_pause_test)) { if (!(i++ & 0xffff)) { set_current_state(TASK_INTERRUPTIBLE); @@ -625,7 +625,6 @@ bool stutter_wait(const char *title) } cond_resched(); } - set_user_nice(current, oldnice); } else { schedule_timeout_interruptible(round_jiffies_relative(HZ)); } -- 2.9.5