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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7840C433F5 for ; Thu, 28 Oct 2021 07:08:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6C6E160FF2 for ; Thu, 28 Oct 2021 07:08:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6C6E160FF2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id F14A66B0071; Thu, 28 Oct 2021 03:08:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EC40A6B0072; Thu, 28 Oct 2021 03:08:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D8BDF940007; Thu, 28 Oct 2021 03:08:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0054.hostedemail.com [216.40.44.54]) by kanga.kvack.org (Postfix) with ESMTP id B3D136B0071 for ; Thu, 28 Oct 2021 03:08:50 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 4AF251817B09A for ; Thu, 28 Oct 2021 07:08:50 +0000 (UTC) X-FDA: 78744968820.07.E9B3B33 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf13.hostedemail.com (Postfix) with ESMTP id A57581049214 for ; Thu, 28 Oct 2021 07:08:43 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 140906103B; Thu, 28 Oct 2021 07:08:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1635404928; bh=NKOgfVI75LT2kYNlTpP+Imw8FP9ky/mWL0iRbt63IFY=; h=From:To:Cc:Subject:Date:In-Reply-To:From; b=IcTTs2pzI1rBl1mGdMHHWabXHzmvKMBHSIrrvOB/b5XyotUao7s7hLyPJAd68TFjK gzqtvyXGeg9Cjqnpg0P5/btMu4b1C4lgfTlHJK6vGuGig5ljCMmP405Pd2n+k3m+Ri p7ABWupvO8x+s+ocT6BdfztEKPBzQ53kfi9+NDSbXZyRQKJTjwtnJg38zlJ9QLRAMF BmDHkzCNOXpj4E9gP1EPaQNVn+RhdQXxqZa0cEi1/wOCrzlH/Bid0aIqcNDLJqPO2K s/72hbenst3ZADM5dbq39xyQFyaq97eo107D6xjmHbqt5CMbuNzYytd3XWanzpjAxR 9ujDF2apI6QhQ== From: SeongJae Park To: Changbin Du Cc: Andrew Morton , SeongJae Park , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/damon: simplify stop mechanism Date: Thu, 28 Oct 2021 07:08:45 +0000 Message-Id: <20211028070845.10445-1-sj@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211027130517.4404-1-changbin.du@gmail.com> X-Stat-Signature: 9yuooaf7fwuysnrxscd5wj7jwet3u1tn X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A57581049214 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=IcTTs2pz; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sj@kernel.org X-HE-Tag: 1635404923-999465 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Thank you for this patch! On Wed, 27 Oct 2021 21:05:17 +0800 Changbin Du wrote: > An kernel thread can exit gracefully with kthread_stop(). So we don't need > a new flag 'kdamond_stop'. And to make sure the task struct is not freed > when accessing it, get reference of it before termination. > > Signed-off-by: Changbin Du Reviewed-by: SeongJae Park Thanks, SJ > --- > include/linux/damon.h | 1 - > mm/damon/core.c | 51 +++++++++++++------------------------------ > 2 files changed, 15 insertions(+), 37 deletions(-) > > diff --git a/include/linux/damon.h b/include/linux/damon.h > index a14b3cc54cab..50c6eb0dee1f 100644 > --- a/include/linux/damon.h > +++ b/include/linux/damon.h > @@ -381,7 +381,6 @@ struct damon_ctx { > > /* public: */ > struct task_struct *kdamond; > - bool kdamond_stop; > struct mutex kdamond_lock; > > struct damon_primitive primitive; > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 46a6afea3030..f37c17b53814 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -390,17 +390,6 @@ static unsigned long damon_region_sz_limit(struct damon_ctx *ctx) > return sz; > } > > -static bool damon_kdamond_running(struct damon_ctx *ctx) > -{ > - bool running; > - > - mutex_lock(&ctx->kdamond_lock); > - running = ctx->kdamond != NULL; > - mutex_unlock(&ctx->kdamond_lock); > - > - return running; > -} > - > static int kdamond_fn(void *data); > > /* > @@ -418,7 +407,6 @@ static int __damon_start(struct damon_ctx *ctx) > mutex_lock(&ctx->kdamond_lock); > if (!ctx->kdamond) { > err = 0; > - ctx->kdamond_stop = false; > ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d", > nr_running_ctxs); > if (IS_ERR(ctx->kdamond)) { > @@ -474,13 +462,15 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs) > */ > static int __damon_stop(struct damon_ctx *ctx) > { > + struct task_struct *tsk; > + > mutex_lock(&ctx->kdamond_lock); > - if (ctx->kdamond) { > - ctx->kdamond_stop = true; > + tsk = ctx->kdamond; > + if (tsk) { > + get_task_struct(tsk); > mutex_unlock(&ctx->kdamond_lock); > - while (damon_kdamond_running(ctx)) > - usleep_range(ctx->sample_interval, > - ctx->sample_interval * 2); > + kthread_stop(tsk); > + put_task_struct(tsk); > return 0; > } > mutex_unlock(&ctx->kdamond_lock); > @@ -925,12 +915,8 @@ static bool kdamond_need_update_primitive(struct damon_ctx *ctx) > static bool kdamond_need_stop(struct damon_ctx *ctx) > { > struct damon_target *t; > - bool stop; > > - mutex_lock(&ctx->kdamond_lock); > - stop = ctx->kdamond_stop; > - mutex_unlock(&ctx->kdamond_lock); > - if (stop) > + if (kthread_should_stop()) > return true; > > if (!ctx->primitive.target_valid) > @@ -1021,13 +1007,6 @@ static int kdamond_wait_activation(struct damon_ctx *ctx) > return -EBUSY; > } > > -static void set_kdamond_stop(struct damon_ctx *ctx) > -{ > - mutex_lock(&ctx->kdamond_lock); > - ctx->kdamond_stop = true; > - mutex_unlock(&ctx->kdamond_lock); > -} > - > /* > * The monitoring daemon that runs as a kernel thread > */ > @@ -1038,17 +1017,18 @@ static int kdamond_fn(void *data) > struct damon_region *r, *next; > unsigned int max_nr_accesses = 0; > unsigned long sz_limit = 0; > + bool done = false; > > pr_debug("kdamond (%d) starts\n", current->pid); > > if (ctx->primitive.init) > ctx->primitive.init(ctx); > if (ctx->callback.before_start && ctx->callback.before_start(ctx)) > - set_kdamond_stop(ctx); > + done = true; > > sz_limit = damon_region_sz_limit(ctx); > > - while (!kdamond_need_stop(ctx)) { > + while (!kdamond_need_stop(ctx) && !done) { > if (kdamond_wait_activation(ctx)) > continue; > > @@ -1056,7 +1036,7 @@ static int kdamond_fn(void *data) > ctx->primitive.prepare_access_checks(ctx); > if (ctx->callback.after_sampling && > ctx->callback.after_sampling(ctx)) > - set_kdamond_stop(ctx); > + done = true; > > usleep_range(ctx->sample_interval, ctx->sample_interval + 1); > > @@ -1069,7 +1049,7 @@ static int kdamond_fn(void *data) > sz_limit); > if (ctx->callback.after_aggregation && > ctx->callback.after_aggregation(ctx)) > - set_kdamond_stop(ctx); > + done = true; > kdamond_apply_schemes(ctx); > kdamond_reset_aggregated(ctx); > kdamond_split_regions(ctx); > @@ -1088,9 +1068,8 @@ static int kdamond_fn(void *data) > damon_destroy_region(r, t); > } > > - if (ctx->callback.before_terminate && > - ctx->callback.before_terminate(ctx)) > - set_kdamond_stop(ctx); > + if (ctx->callback.before_terminate) > + ctx->callback.before_terminate(ctx); > if (ctx->primitive.cleanup) > ctx->primitive.cleanup(ctx); > > -- > 2.32.0 >