From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <SRS0=8NXk=ZD=paulmck-ThinkPad-P17-Gen-1.home=paulmck@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org
X-Spam-Level:
X-Spam-Status: No, score=-6.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,
SPF_PASS autolearn=ham autolearn_force=no version=3.4.6
Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75])
by gnuweeb.org (Postfix) with ESMTPS id ADCEA80BBF
for <gwml@vger.gnuweeb.org>; Wed, 31 Aug 2022 18:21:53 +0000 (UTC)
Authentication-Results: gnuweeb.org;
dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=SVBHJbpN;
dkim-atps=neutral
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 ams.source.kernel.org (Postfix) with ESMTPS id 63273B82221;
Wed, 31 Aug 2022 18:21:51 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20F8FC433C1;
Wed, 31 Aug 2022 18:21:50 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
s=k20201202; t=1661970110;
bh=G6VCAaAlg/8tBYkx3RPV5CkGGSZS3E5wZVxJmH+lP90=;
h=From:To:Cc:Subject:Date:In-Reply-To:References:From;
b=SVBHJbpNQdgbnc4qXYLa+ovth+GIPc7SCLhCOA6jS5UqRAf/NBnMuaRtX2GsKQV7m
hpi2tqu1Sd+z1oP7yFNBuQSEKCFrIIlQa2R8hZmAGWK7q6uo8HhxxapcLBYR78jC7q
Pei9AcypNaKfMPjIMe8csMI+ZQGbIUHCBSyvFiMNbu8EB+K3bA+QOy8fRX06rNqLZn
BhM/pRcBsQ7QuoerunDb6speRipO+PJP4aofMvvifHF59W3gDsrvyX532HFUYeGT3N
op0KYOvA6VDi8UBetIc2CnfTA+hq1JuXgYOXaiXGozu5+61Zuc7z+KRym/2P9koOaj
jWyQxvf2sK78A==
Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000)
id D16295C0143; Wed, 31 Aug 2022 11:21:49 -0700 (PDT)
From: "Paul E. McKenney" <paulmck@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: gwml@vger.gnuweeb.org,
kernel-team@fb.com,
w@lwt.eu,
"Paul E. McKenney" <paulmck@kernel.org>,
John Ogness <john.ogness@linutronix.de>
Subject: [PATCH rcu 1/2] torture: Optionally flush printk() buffers before powering off
Date: Wed, 31 Aug 2022 11:21:30 -0700
Message-Id: <20220831182148.2698489-2-paulmck@kernel.org>
X-Mailer: git-send-email 2.31.1.189.g2e36527f23
In-Reply-To: <20220831182113.GA2697286@paulmck-ThinkPad-P17-Gen-1>
References: <20220831182113.GA2697286@paulmck-ThinkPad-P17-Gen-1>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
List-Id: <gwml.vger.gnuweeb.org>
The rcutorture test suite produces quite a bit of console output at
the end of a test. This means that the new-in-2022 printk() kthreads
are likely to be in the process of flushing output at the time of the
torture_shutdown() function's call to kernel_power_off(). Normally,
rcutorture relies on printk() to flush any pending output upon shutdown,
the better to detect bugs in this area, for example, the one introduced
by 8e274732115f ("printk: extend console_lock for per-console locking").
However, once such a bug is detected and reported, it is necessary to
test the rest of the system, without noise from the already-reported bug.
This commit therefore adds a torture.printk_shutdown_bug_workaround
kernel parameter, which causes torture_shutdown() to invoke pr_flush(),
and print an informative message on the console, immediately before
invoking kernel_power_off(). When this kernel parameter is not specified,
it is up to printk() to flush its own buffers.
Suggested-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
kernel/torture.c | 7 +++++++
2 files changed, 13 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d7f30902fda02..ba1b8776aab83 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6143,6 +6143,12 @@
are running concurrently, especially on systems
with rotating-rust storage.
+ torture.printk_shutdown_bug_workaround= [KNL]
+ Execute pr_flush(1000, true) just before invoking
+ kernel_power_off() to work around any bugs that
+ might prevent printk() from flushing its buffers
+ at shutdown time.
+
torture.verbose_sleep_frequency= [KNL]
Specifies how many verbose printk()s should be
emitted between each sleep. The default of zero
diff --git a/kernel/torture.c b/kernel/torture.c
index 789aeb0e1159c..7cd2016b02076 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -48,6 +48,9 @@ module_param(disable_onoff_at_boot, bool, 0444);
static bool ftrace_dump_at_shutdown;
module_param(ftrace_dump_at_shutdown, bool, 0444);
+static bool printk_shutdown_bug_workaround;
+module_param(printk_shutdown_bug_workaround, bool, 0444);
+
static int verbose_sleep_frequency;
module_param(verbose_sleep_frequency, int, 0444);
@@ -651,6 +654,10 @@ static int torture_shutdown(void *arg)
VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
if (ftrace_dump_at_shutdown)
rcu_ftrace_dump(DUMP_ALL);
+ if (printk_shutdown_bug_workaround) {
+ pr_info("%s: Flushing printk() buffers at power-down time.\n", __func__);
+ pr_flush(1000, true);
+ }
kernel_power_off(); /* Shut down the system. */
return 0;
}
--
2.31.1.189.g2e36527f23