From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99DB81DB95E; Fri, 20 Mar 2026 15:41:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774021296; cv=none; b=fPXAUxAqSEjI60lPP9zxMKs+6nJp4WJGmfnzIjSIpCimGlZX4aMjuyvfFcjjNFEesmV4AC/2kgSs7nhXgKv54/QqwJTfV85Pjx2pX3HV3xBJsL4ZMHV1xLjNKGoNbkH1VPMyAEcYZidERTasZKnUhesUN+cZJIPN41dKyrVgUmY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774021296; c=relaxed/simple; bh=81ZkqAUVnlz41ptZj/553F+xUS7ey1nMbeOLZES5vfo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Nvi9bgEU2theWON/IiKXNTaH/a8bCX1JpL0IaVCYFjfekIP/ZVWubYOQuUPxVcjUFTnn+6xKnlju+uJzsgZT2ZZ5XDjgFfmYcReDAOW/o3ynkGqAnlcf/Dy0XjSYayazcHSl5avBqDJ1Lw//QWHrW5JZ+ja4hXbo4CWO6ItrAnM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uweqh+aw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uweqh+aw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29FA6C19425; Fri, 20 Mar 2026 15:41:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774021296; bh=81ZkqAUVnlz41ptZj/553F+xUS7ey1nMbeOLZES5vfo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uweqh+awyWzU6l9rWmraVnYcvbpC5Gum/rABVstH2RtHPHHtfj0saBZI7jw8hoKjO jPIYxky/Er/Vg0q0gIVrcRgSGEQxTMr6CtGP2mYynkoXgn7aDCjgQ8bcyiZwyfWHPw tIa2wy/r5tj63S63ajm2BWVqLx5+VUdXR44ehbZFEe9tOIdgHwAQHPtQhfLd8SQXTq TaeOFQibOHTeTUBku4ljNBj5O3AEm6tvc/pgr+FAAtyTqWOzrTrEgkHmxt94T7uZf1 Vef1ULORT1iF36/Ek6Sp9ujMcSUG3L/MqODGzRnXCO1AxR/zNm/BzfU4yHHMeqohWX b06IyCk/h2JTQ== From: SeongJae Park To: SeongJae Park Cc: Shuah Khan , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v2 10/10] selftets/damon/sysfs.py: pause DAMON before dumping status Date: Fri, 20 Mar 2026 08:41:33 -0700 Message-ID: <20260320154134.99740-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260320152940.99417-1-sj@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Fri, 20 Mar 2026 08:29:39 -0700 SeongJae Park wrote: > Adding Sashiko comment > (https://lore.kernel.org/https://sashiko.dev/#/patchset/20260319052157.99433-11-sj@kernel.org) > with ': ' line prefix, and my replies in line. > > On Wed, 18 Mar 2026 22:21:53 -0700 SeongJae Park wrote: > > > The sysfs.py test commits DAMON parameters, dump the internal DAMON > > state, and show if the parameters are committed as expected using the > > dumped state. While the dumping is ongoing, DAMON is alive. It can > > make internal changes including addition and removal of regions. It can > > therefore make a race that can result in false test results. Pause > > DAMON execution during the state dumping to avoid such races. > > > > Signed-off-by: SeongJae Park > > --- > > tools/testing/selftests/damon/sysfs.py | 31 ++++++++++++++++++++++++++ > > 1 file changed, 31 insertions(+) > > > > diff --git a/tools/testing/selftests/damon/sysfs.py b/tools/testing/selftests/damon/sysfs.py > > index e6d34ba05893f..704729c7a318e 100755 > > --- a/tools/testing/selftests/damon/sysfs.py > > +++ b/tools/testing/selftests/damon/sysfs.py > > @@ -193,18 +193,48 @@ def assert_ctx_committed(ctx, dump): > > assert_true(dump['pause'] == ctx.pause, 'pause', dump) > > > > def assert_ctxs_committed(kdamonds): > > + ctxs_paused_for_dump = [] > > + for kd in kdamonds.kdamonds: > > + for ctx in kd.contexts: > > + if ctx.pause is False: > > + ctx.pause = True > > + err = kd.commit() > > + if err is not None: > > + print('pause fail (%s)' % err) > > + kdamonds.stop() > > + exit(1) > > + ctxs_paused_for_dump.append(ctx) > > + > > status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid) > > if err is not None: > > print(err) > > kdamonds.stop() > > exit(1) > > > > + for kd in kdamonds.kdamonds: > > + for ctx in kd.contexts: > > + if ctx in ctxs_paused_for_dump: > > + ctx.pause = False > > + err = kd.commit() > > + if err is not None: > > + print('resume fail (%s)' % err) > > + kdamonds.stop() > > + exit(1) > > + # restore for comparison > > + ctx.pause = True > > : If a kdamond contains multiple contexts, does this loop leave earlier contexts > : paused in the kernel? > : > : Since kd.commit() stages and commits the state of all contexts associated with > : the kdamond, when kd.commit() is called for the second context, the first > : context's local pause attribute is already back to True. > : > : This would cause kd.commit() to write to sysfs and instruct the kernel to > : pause the first context again. By the end of this loop, only the last context > : in the kdamond would remain unpaused in the kernel. > > No. The pause field of the earlier context is set to False, so later > kd.commit() will commit the False 'pause' again. But this finds a good point. > There is no reason to call kd.commit() for each context. It is more efficient > to be called for each kdamond., thouth currently we support only one context > per kdamond. I will update the code so, in the next spin. I'm wrong, Sashiko is correct. I missed the last 'ctx.pause = True' in the loop. I will fix this together, like below: ''' --- a/tools/testing/selftests/damon/sysfs.py +++ b/tools/testing/selftests/damon/sysfs.py @@ -201,16 +201,17 @@ def assert_ctx_committed(ctx, dump): def assert_ctxs_committed(kdamonds): ctxs_paused_for_dump = [] + # pause for safe state dumping for kd in kdamonds.kdamonds: for ctx in kd.contexts: if ctx.pause is False: ctx.pause = True - err = kd.commit() - if err is not None: - print('pause fail (%s)' % err) - kdamonds.stop() - exit(1) ctxs_paused_for_dump.append(ctx) + err = kd.commit() + if err is not None: + print('pause fail (%s)' % err) + kdamonds.stop() + exit(1) status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid) if err is not None: @@ -218,17 +219,19 @@ def assert_ctxs_committed(kdamonds): kdamonds.stop() exit(1) + # resume contexts paused for safe state dumping for kd in kdamonds.kdamonds: - for ctx in kd.contexts: - if ctx in ctxs_paused_for_dump: - ctx.pause = False - err = kd.commit() - if err is not None: - print('resume fail (%s)' % err) - kdamonds.stop() - exit(1) - # restore for comparison - ctx.pause = True + for ctx in ctxs_paused_for_dump: + ctx.pause = False + err = kd.commit() + if err is not None: + print('resume fail (%s)' % err) + kdamonds.stop() + exit(1) + + # restore for comparison + for ctx in ctxs_paused_for_dump: + ctx.pause = True ctxs = kdamonds.kdamonds[0].contexts dump = status['contexts'] ''' Thanks, SJ [...]