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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id v24sm19554611qtq.14.2020.01.21.11.09.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Jan 2020 11:09:06 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3608.40.2.2.4\)) Subject: Re: Boot warning at rcu_check_gp_start_stall() From: Qian Cai In-Reply-To: <20200121161533.GT2935@paulmck-ThinkPad-P72> Date: Tue, 21 Jan 2020 14:09:05 -0500 Cc: rcu@vger.kernel.org, LKML Content-Transfer-Encoding: quoted-printable Message-Id: <6A6B0325-64C4-4470-91B4-37104CF8DA1A@lca.pw> References: <20200121141923.GP2935@paulmck-ThinkPad-P72> <20200121161533.GT2935@paulmck-ThinkPad-P72> To: "Paul E. McKenney" X-Mailer: Apple Mail (2.3608.40.2.2.4) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org > On Jan 21, 2020, at 11:15 AM, Paul E. McKenney = wrote: >=20 > On Tue, Jan 21, 2020 at 09:37:13AM -0500, Qian Cai wrote: >>=20 >>=20 >>> On Jan 21, 2020, at 9:19 AM, Paul E. McKenney = wrote: >>>=20 >>> One approach would be to boot with = rcupdate.rcu_cpu_stall_timeout=3D300, >>> which would allow more time. >>=20 >> It works for me if once that warning triggered, give a bit = information about adjusting the parameter when debugging options are on = to suppress the warning due to expected long boot. >=20 > Indeed. 300 seconds as shown above is currently the maximum, but > please let me know if it needs to be increased. This module parameter > is writable after boot via sysfs, so maybe that could be part of the > workaround. >=20 >>> Longer term, I could suppress this warning during boot when >>> CONFIG_EFI_PGT_DUMP=3Dy, but that sounds quite specific. = Alternatively, >>> I could provide a Kconfig option that suppressed this during boot >>> that was selected by whatever long-running boot-time Kconfig option >>> needed it. Yet another approach would be for long-running = operations >>> like efi_dump_pagetable() to suppress stalls on entry and re-enable = them >>> upon exit. >>>=20 >>> Thoughts? >>=20 >> None of the options sounds particularly better for me because there = could come up with other options may trigger this, memtest comes in = mind, for example. Then, it is a bit of pain to maintain of unknown. >=20 > I was afraid of that. ;-) >=20 > Could you please send me the full dmesg up to that point? No = promises, > but it might well be that I can make some broad-spectrum adjustment > within RCU. Only one way to find out=E2=80=A6 https://cailca.github.io/files/dmesg.txt