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 D7295C433EF for ; Sat, 23 Apr 2022 17:39:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236638AbiDWRmN (ORCPT ); Sat, 23 Apr 2022 13:42:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236599AbiDWRmN (ORCPT ); Sat, 23 Apr 2022 13:42:13 -0400 Received: from mail-pg1-x52b.google.com (mail-pg1-x52b.google.com [IPv6:2607:f8b0:4864:20::52b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F21501C82D1 for ; Sat, 23 Apr 2022 10:39:15 -0700 (PDT) Received: by mail-pg1-x52b.google.com with SMTP id q19so9912644pgm.6 for ; Sat, 23 Apr 2022 10:39:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=lEau4k6lbTQ9lqJfBFgL32mD1tqEjCcVozijP5814T8=; b=k8/X2Umrw7Sadwq9rV1w2TrOyZ5jKQ/v0Xw4Enl6ltcqaYox4ZDUyUsPuAZs4wzdBU C6JQKeciWrv+zzaLMGRV5FaDY6wrQGtPkZ/6J9wc4ada/GlFM86qp5L8W5dNPh7+T+Q1 Th1O0CtuZZaSEe2akZy/y6lI2kL/cRkTPNgACapVoX0i9r5Vk3vneNqJJQ+wakrSVg2I zJx5dVQMxJZfQRAf79O61Fn83OmbBRIJNbch/6XgaHf2+YhKxtLnIGfzobN8N7JulKzb 3s/ll03IVnAbML0iivKFz2rZozCwE2rvgKXtNmjpquvWc2km/YgiSIPDRuaFpZDENlSw HhoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=lEau4k6lbTQ9lqJfBFgL32mD1tqEjCcVozijP5814T8=; b=IXZCn/KURSOtKMWo/5WvbbESFR/tyzIPmfbHVpAih4CKxC84wWRNA9rwahxTESXiyN e5nKRVGL2LydxGfn8JuXzo0mK5WmKiAFsafsagNyew7h2gKSq+EP5jFi8iO5CH+wWDKl DTV1wvPjriRtwSWt83nrq8EZQnW8MQS4E4iBNYMvvrXYr6I+vtOQOtaAwiyY15isOUKN eguDkORkn6Xuav/9Hy7RzBTsqR7n1re0n5aFohVpSppO/edwX6ZFgJWoQtmXag2s7kbP 1Q9wxVxF2nfS/rvdcLaH8d+Zxxr8UeGnF2Lc/GHD9kIokrF8jgrn+cPzH69Cji1ro5Qf xXpw== X-Gm-Message-State: AOAM532vG1+JkIhPlGAq8W1vDvNy66lkyLXlCEOLAz85qUlY4Ee3zjx6 wAsodWfwZ6T2ZK/oxmNO7ZtcYISGjLlXDF79 X-Google-Smtp-Source: ABdhPJzH9qtteNL0vmTeiVg1Li+r+zywJOMcUWj0ZL8byvLD/lrrQ2jctdR7UFgBF7kS8xqb3DWfUg== X-Received: by 2002:a63:b24c:0:b0:398:9594:a140 with SMTP id t12-20020a63b24c000000b003989594a140mr8862916pgo.292.1650735555104; Sat, 23 Apr 2022 10:39:15 -0700 (PDT) Received: from localhost.localdomain ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id e16-20020a63ee10000000b0039d1c7e80bcsm5198854pgi.75.2022.04.23.10.39.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 Apr 2022 10:39:14 -0700 (PDT) From: Jens Axboe To: io-uring@vger.kernel.org Cc: Jens Axboe Subject: [PATCH 1/5] task_work: allow TWA_SIGNAL without a rescheduling IPI Date: Sat, 23 Apr 2022 11:39:07 -0600 Message-Id: <20220423173911.651905-2-axboe@kernel.dk> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220423173911.651905-1-axboe@kernel.dk> References: <20220423173911.651905-1-axboe@kernel.dk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Some use cases don't always need an IPI when sending a TWA_SIGNAL notification. Add TWA_SIGNAL_NO_IPI, which is just like TWA_SIGNAL, except it doesn't send an IPI to the target task. It merely sets TIF_NOTIFY_SIGNAL and wakes up the task. Signed-off-by: Jens Axboe --- include/linux/sched/signal.h | 13 +++++++++++-- include/linux/task_work.h | 1 + kernel/task_work.c | 15 ++++++++++----- 3 files changed, 22 insertions(+), 7 deletions(-) diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 3c8b34876744..66b689f6cfcb 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -355,14 +355,23 @@ static inline void clear_notify_signal(void) smp_mb__after_atomic(); } +/* + * Returns 'true' if kick_process() is needed to force a transition from + * user -> kernel to guarantee expedient run of TWA_SIGNAL based task_work. + */ +static inline bool __set_notify_signal(struct task_struct *task) +{ + return !test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) && + !wake_up_state(task, TASK_INTERRUPTIBLE); +} + /* * Called to break out of interruptible wait loops, and enter the * exit_to_user_mode_loop(). */ static inline void set_notify_signal(struct task_struct *task) { - if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) && - !wake_up_state(task, TASK_INTERRUPTIBLE)) + if (__set_notify_signal(task)) kick_process(task); } diff --git a/include/linux/task_work.h b/include/linux/task_work.h index 897494b597ba..795ef5a68429 100644 --- a/include/linux/task_work.h +++ b/include/linux/task_work.h @@ -17,6 +17,7 @@ enum task_work_notify_mode { TWA_NONE, TWA_RESUME, TWA_SIGNAL, + TWA_SIGNAL_NO_IPI, }; static inline bool task_work_pending(struct task_struct *task) diff --git a/kernel/task_work.c b/kernel/task_work.c index c59e1a49bc40..fa8fdd04aa17 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -13,11 +13,13 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */ * * Queue @work for task_work_run() below and notify the @task if @notify * is @TWA_RESUME or @TWA_SIGNAL. @TWA_SIGNAL works like signals, in that the - * it will interrupt the targeted task and run the task_work. @TWA_RESUME - * work is run only when the task exits the kernel and returns to user mode, - * or before entering guest mode. Fails if the @task is exiting/exited and thus - * it can't process this @work. Otherwise @work->func() will be called when the - * @task goes through one of the aforementioned transitions, or exits. + * it will interrupt the targeted task and run the task_work. @TWA_SIGNAL_NO_IPI + * works like @TWA_SIGNAL, except it doesn't send a reschedule IPI to force the + * targeted task to reschedule and run task_work. @TWA_RESUME work is run only + * when the task exits the kernel and returns to user mode, or before entering + * guest mode. Fails if the @task is exiting/exited and thus it can't process + * this @work. Otherwise @work->func() will be called when the @task goes + * through one of the aforementioned transitions, or exits. * * If the targeted task is exiting, then an error is returned and the work item * is not queued. It's up to the caller to arrange for an alternative mechanism @@ -53,6 +55,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work, case TWA_SIGNAL: set_notify_signal(task); break; + case TWA_SIGNAL_NO_IPI: + __set_notify_signal(task); + break; default: WARN_ON_ONCE(1); break; -- 2.35.1