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Wed, 9 Oct 2019 13:51:56 +0000 (UTC) Date: Wed, 9 Oct 2019 15:51:55 +0200 From: Michal Hocko To: Qian Cai Cc: Petr Mladek , Christian Borntraeger , Heiko Carstens , sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, john.ogness@linutronix.de, akpm@linux-foundation.org, Vasily Gorbik , Peter Oberparleiter , david@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Message-ID: <20191009135155.GC6681@dhcp22.suse.cz> References: <1570550917.5576.303.camel@lca.pw> <20191008183525.GQ6681@dhcp22.suse.cz> <1570561573.5576.307.camel@lca.pw> <20191008191728.GS6681@dhcp22.suse.cz> <1570563324.5576.309.camel@lca.pw> <20191009114903.aa6j6sa56z2cssom@pathway.suse.cz> <1570626402.5937.1.camel@lca.pw> <20191009132746.GA6681@dhcp22.suse.cz> <1570628593.5937.3.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1570628593.5937.3.camel@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000110, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 09-10-19 09:43:13, Qian Cai wrote: > On Wed, 2019-10-09 at 15:27 +0200, Michal Hocko wrote: > > On Wed 09-10-19 09:06:42, Qian Cai wrote: > > [...] > > > https://lore.kernel.org/linux-mm/1570460350.5576.290.camel@lca.pw/ > > >=20 > > > [=A0=A0297.425964] -> #1 (&port_lock_key){-.-.}: > > > [=A0=A0297.425967]=A0=A0=A0=A0=A0=A0=A0=A0__lock_acquire+0x5b3/0xb4= 0 > > > [=A0=A0297.425967]=A0=A0=A0=A0=A0=A0=A0=A0lock_acquire+0x126/0x280 > > > [=A0=A0297.425968]=A0=A0=A0=A0=A0=A0=A0=A0_raw_spin_lock_irqsave+0x= 3a/0x50 > > > [=A0=A0297.425969]=A0=A0=A0=A0=A0=A0=A0=A0serial8250_console_write+= 0x3e4/0x450 > > > [=A0=A0297.425970]=A0=A0=A0=A0=A0=A0=A0=A0univ8250_console_write+0x= 4b/0x60 > > > [=A0=A0297.425970]=A0=A0=A0=A0=A0=A0=A0=A0console_unlock+0x501/0x75= 0 > > > [=A0=A0297.425971]=A0=A0=A0=A0=A0=A0=A0=A0vprintk_emit+0x10d/0x340 > > > [=A0=A0297.425972]=A0=A0=A0=A0=A0=A0=A0=A0vprintk_default+0x1f/0x30 > > > [=A0=A0297.425972]=A0=A0=A0=A0=A0=A0=A0=A0vprintk_func+0x44/0xd4 > > > [=A0=A0297.425973]=A0=A0=A0=A0=A0=A0=A0=A0printk+0x9f/0xc5 > > > [=A0=A0297.425974]=A0=A0=A0=A0=A0=A0=A0=A0register_console+0x39c/0x= 520 > > > [=A0=A0297.425975]=A0=A0=A0=A0=A0=A0=A0=A0univ8250_console_init+0x2= 3/0x2d > > > [=A0=A0297.425975]=A0=A0=A0=A0=A0=A0=A0=A0console_init+0x338/0x4cd > > > [=A0=A0297.425976]=A0=A0=A0=A0=A0=A0=A0=A0start_kernel+0x534/0x724 > > > [=A0=A0297.425977]=A0=A0=A0=A0=A0=A0=A0=A0x86_64_start_reservations= +0x24/0x26 > > > [=A0=A0297.425977]=A0=A0=A0=A0=A0=A0=A0=A0x86_64_start_kernel+0xf4/= 0xfb > > > [=A0=A0297.425978]=A0=A0=A0=A0=A0=A0=A0=A0secondary_startup_64+0xb6= /0xc0 > > >=20 > > > where=A0the report again show the early boot call trace for the loc= king > > > dependency, > > >=20 > > > console_owner --> port_lock_key > > >=20 > > > but that dependency clearly not only happen in the early boot. > >=20 > > Can you provide an example of the runtime dependency without any earl= y > > boot artifacts? Because this discussion really doens't make much sens= e > > without a clear example of a _real_ lockdep report that is not a fals= e > > possitive. All of them so far have been concluded to be false possiti= ve > > AFAIU. >=20 > An obvious one is in the above link. Just replace the trace in #1 above= with > printk() from anywhere, i.e., just ignore the early boot calls there as= they are > not important. >=20 > printk() > console_unlock() > console_lock_spinning_enable() --> console_owner_lock > call_console_drivers() > serial8250_console_write() --> port->lock Can you paste the full lock chain graph to be sure we are on the same page? --=20 Michal Hocko SUSE Labs