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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E347C4332F for ; Mon, 13 Dec 2021 14:20:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234560AbhLMOU5 (ORCPT ); Mon, 13 Dec 2021 09:20:57 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:42366 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239028AbhLMOUm (ORCPT ); Mon, 13 Dec 2021 09:20:42 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4AA5761113; Mon, 13 Dec 2021 14:20:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80301C34603; Mon, 13 Dec 2021 14:20:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1639405241; bh=6KVcvYdTKvmWEQjY+NaF3Ez9oO/095PO4ec0T6zRuZk=; h=From:To:Cc:Subject:Date:From; b=pc/SKUoEla86h67UGGFeXbHW0MKQRiRa78XwdHoYTXY4hlPFDNqmyDQkqzJI4Hmc4 WEZKo68p/dkABxBCYzqRuugNzNc0Gxw0JaIuU/fKjCpqY8Was1X2Wf85LmQN9GHscl 6r4s06rZjEnUgz8zNXAt5UtofpvdAfcue5qjDGCISRafoAW/81Vhp0zt9Okh247CX9 frNffvsU6u6V7LAvajPfQ5KM6ZgcrWmhrBBGUtY64Zvp4E3IDvGUyvt8RyFIcU1Y3U RTkt6+8fF2iEisuVbLLuT7qFWL1BOy+W5SjKGzPh9K8Iu/khDzDswiVWOQbVGb7R4c rEic97QhrvjAA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Frederic Weisbecker , Hasegawa Hitomi , Thomas Gleixner , Masayoshi Mizuma , Phil Auld , Sasha Levin , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org Subject: [PATCH MANUALSEL 5.4 1/2] sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full Date: Mon, 13 Dec 2021 09:20:26 -0500 Message-Id: <20211213142028.352438-1-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Frederic Weisbecker [ Upstream commit e7f2be115f0746b969c0df14c0d182f65f005ca5 ] getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime than the actual time. task_cputime_adjusted() snapshots utime and stime and then adjust their sum to match the scheduler maintained cputime.sum_exec_runtime. Unfortunately in nohz_full, sum_exec_runtime is only updated once per second in the worst case, causing a discrepancy against utime and stime that can be updated anytime by the reader using vtime. To fix this situation, perform an update of cputime.sum_exec_runtime when the cputime snapshot reports the task as actually running while the tick is disabled. The related overhead is then contained within the relevant situations. Reported-by: Hasegawa Hitomi Signed-off-by: Frederic Weisbecker Signed-off-by: Hasegawa Hitomi Signed-off-by: Thomas Gleixner Tested-by: Masayoshi Mizuma Acked-by: Phil Auld Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org Signed-off-by: Sasha Levin --- include/linux/sched/cputime.h | 5 +++-- kernel/sched/cputime.c | 12 +++++++++--- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/include/linux/sched/cputime.h b/include/linux/sched/cputime.h index 6c9f19a33865a..ce3c58286062c 100644 --- a/include/linux/sched/cputime.h +++ b/include/linux/sched/cputime.h @@ -18,15 +18,16 @@ #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */ #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN -extern void task_cputime(struct task_struct *t, +extern bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime); extern u64 task_gtime(struct task_struct *t); #else -static inline void task_cputime(struct task_struct *t, +static inline bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime) { *utime = t->utime; *stime = t->stime; + return false; } static inline u64 task_gtime(struct task_struct *t) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 46ed4e1383e21..a7ebf0d8e369f 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -666,7 +666,8 @@ void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st) .sum_exec_runtime = p->se.sum_exec_runtime, }; - task_cputime(p, &cputime.utime, &cputime.stime); + if (task_cputime(p, &cputime.utime, &cputime.stime)) + cputime.sum_exec_runtime = task_sched_runtime(p); cputime_adjust(&cputime, &p->prev_cputime, ut, st); } EXPORT_SYMBOL_GPL(task_cputime_adjusted); @@ -859,19 +860,21 @@ u64 task_gtime(struct task_struct *t) * add up the pending nohz execution time since the last * cputime snapshot. */ -void task_cputime(struct task_struct *t, u64 *utime, u64 *stime) +bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime) { struct vtime *vtime = &t->vtime; unsigned int seq; u64 delta; + int ret; if (!vtime_accounting_enabled()) { *utime = t->utime; *stime = t->stime; - return; + return false; } do { + ret = false; seq = read_seqcount_begin(&vtime->seqcount); *utime = t->utime; @@ -881,6 +884,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime) if (vtime->state == VTIME_INACTIVE || is_idle_task(t)) continue; + ret = true; delta = vtime_delta(vtime); /* @@ -892,5 +896,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime) else if (vtime->state == VTIME_SYS) *stime += vtime->stime + delta; } while (read_seqcount_retry(&vtime->seqcount, seq)); + + return ret; } #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */ -- 2.33.0