LinuxPPC-Dev Archive on lore.kernel.org
 help / color / Atom feed
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Dmitry Safonov <dima@arista.com>
Cc: Juri Lelli <juri.lelli@redhat.com>,
	linux-sh@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ben Segall <bsegall@google.com>, Guo Ren <guoren@kernel.org>,
	Pavel Machek <pavel@ucw.cz>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Paul Burton <paulburton@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Mel Gorman <mgorman@suse.de>, Jiri Slaby <jslaby@suse.com>,
	Matt Turner <mattst88@gmail.com>,
	uclinux-h8-devel@lists.sourceforge.jp,
	Len Brown <len.brown@intel.com>,
	linux-pm@vger.kernel.org,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux-um@lists.infradead.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Richard Henderson <rth@twiddle.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	LKML <linux-kernel@vger.kernel.org>,
	Ralf Baechle <ralf@linux-mips.org>,
	Paul Mackerras <paulus@samba.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-ia64@vger.kernel.org,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	James Hogan <jhogan@kernel.org>,
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	Max Filippov <jcmvbkbc@gmail.com>,
	Vincent Chen <deanbo422@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	linux-s390@vger.kernel.org, linux-c6x-dev@linux-c6x.org,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	linux-hexagon@vger.kernel.org, Helge Deller <deller@gmx.de>,
	"open list:TENSILICA XTENSA PORT \(xtensa\)"
	<linux-xtensa@linux-xtensa.org>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Aurelien Jacquiot <jacquiot.aurelien@gmail.com>,
	linux-m68k@lists.linux-m68k.org,
	Stafford Horne <shorne@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	Chris Zankel <chris@zankel.net>, Tony Luck <tony.luck@intel.com>,
	Douglas Anderson <dianders@chromium.org>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Will Deacon <will@kernel.org>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Brian Cain <bcain@codeaurora.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	kgdb-bugreport@lists.sourceforge.net,
	linux-snps-arc@lists.infradead.org,
	Fenghua Yu <fenghua.yu@intel.com>, Borislav Petkov <bp@alien8.de>,
	Jeff Dike <jdike@addtoit.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Greentime Hu <green.hu@gmail.com>, Guan Xuetao <gxt@pku.edu.cn>,
	linux-parisc@vger.kernel.org, linux-alpha@vger.kernel.org,
	Ley Foon Tan <lftan@altera.com>,
	"David S. Miller" <davem@davemloft.net>,
	Rich Felker <dalias@libc.org>, Petr Mladek <pmladek@suse.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Jonas Bonn <jonas@southpole.se>,
	Richard Weinberger <richard@nod.at>, X86 ML <x86@kernel.org>,
	clang-built-linux@googlegroups.com,
	Ingo Molnar <mingo@redhat.com>, Mark Salter <msalter@redhat.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	openrisc@lists.librecores.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Michal Simek <monstr@monstr.eu>,
	Vineet Gupta <vgupta@synopsys.com>,
	linux-mips@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Jason Wessel <jason.wessel@windriver.com>,
	nios2-dev@lists.rocketboards.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 00/50] Add log level to show_stack()
Date: Fri, 8 Nov 2019 17:30:45 +0000
Message-ID: <20191108173045.GY25745@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAGrbwDRgX1BZoFrVYSXhAeeUKHrB=q3w8jXFPOuRvO7HV4Ciqw@mail.gmail.com>

On Fri, Nov 08, 2019 at 04:28:30PM +0000, Dmitry Safonov wrote:
> On 11/6/19 8:34 PM, Peter Zijlstra wrote:
> > On Wed, Nov 06, 2019 at 04:27:33PM +0000, Dmitry Safonov wrote:
> [..]
> >> Sorry, I should have tried to describe better.
> >>
> >> I'm trying to remove external users of console_loglevel by following
> >> reasons:
> >
> > I suppose since all my machines have 'debug ignore_loglevel
> > earlyprintk=serial,ttyS0,115200 console=ttyS0,115200' I don't have this
> > experience.
> 
> Yeah, I remember you avoid all those functionalities of printk(), fair
> enough. On the other side, regular users and I'm betting most of
> the non-tuned distributions use /proc/sys/kernel/printk by default.
> (Checking on my Arch & Fedora - loglevel 4 from the box)
> 
> >> - changing console_loglevel on SMP means that unwanted messages from
> >> other CPUs will appear (that have lower log level)
> >> - on UMP unwanted messages may appear if the code is preempted while it
> >> hasn't set the console_loglevel back to old
> >> - rising console_loglevel to print wanted message(s) may not work at all
> >> if printk() has being delayed and the console_loglevel is already set
> >> back to old value
> >
> > Sure, frobbing the global console_loglevel is bad.
> >
> >> I also have patches in wip those needs to print backtrace with specific
> >> loglevel (higher when it's critical, lower when it's notice and
> >> shouldn't go to serial console).
> >
> > (everything always should go to serial, serial is awesome :-)
> 
> Personally I agree. Unfortunately, here @Arista there are switches (I'm
> speaking about the order of thousands at least) those have baud-rate 9600.
> It's a bit expensive being elaborate with such setup.
> 
> >> Besides on local tests I see hits those have headers (messages like
> >> "Backtrace: ") without an actual backtrace and the reverse - a backtrace
> >> without a reason for it. It's quite annoying and worth addressing by
> >> syncing headers log levels to backtraces.
> >
> > I suppose I'm surprised there are backtraces that are not important.
> > Either badness happened and it needs printing, or the user asked for it
> > and it needs printing.
> >
> > Perhaps we should be removing backtraces if they're not important
> > instead of allowing to print them as lower loglevels?
> 
> Well, the use-case for lower log-level is that everything goes into logs
> (/var/log/dmesg or /var/log/messages whatever rsyslog has settting).
> 
> That has it's value:
> - after a failure (i.e. panic) messages, those were only signs that
> something goes wrong can be seen in logs which can give ideas what has
> happened.

No they don't.  When the kernel panics, userspace generally stops
running, so rsyslog won't be able to write them to /var/log/messages.

How, by "kernel panics" I mean a real kernel panic, which probably
isn't what you're talking about there.  You are probably talking
about the whole shebang of non-fatal kernel oops, kernel warnings
and the like.  If so, I'd ask you to stop confuzzilating terminology.

If you really want to capture such events, then you need to have the
kernel write the panic to (e.g.) flash - see the mtdoops driver.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up

  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-06  3:04 Dmitry Safonov
2019-11-06  3:05 ` [PATCH 26/50] powerpc: Add show_stack_loglvl() Dmitry Safonov
2019-11-06  9:52   ` Michael Ellerman
2019-11-06 16:01     ` Dmitry Safonov
2019-11-06  8:35 ` [PATCH 00/50] Add log level to show_stack() Petr Mladek
2019-11-06 16:12   ` Dmitry Safonov
2019-11-08 10:37   ` Sergey Senozhatsky
2019-11-08 13:04     ` Petr Mladek
2019-11-11  1:23       ` Sergey Senozhatsky
2019-11-11  9:12         ` Petr Mladek
2019-11-12  4:44           ` Sergey Senozhatsky
2019-11-12  4:57             ` Sergey Senozhatsky
2019-11-12  8:35               ` Petr Mladek
2019-11-12 10:12                 ` Sergey Senozhatsky
2019-11-13  1:23                   ` Sergey Senozhatsky
2019-11-13  2:25                     ` Dmitry Safonov
2019-11-13  6:33                       ` Sergey Senozhatsky
2019-11-13  8:47                         ` Petr Mladek
2019-11-13 16:24                           ` Steven Rostedt
2019-11-13 16:40                         ` Dmitry Safonov
2019-11-15  0:50                           ` Sergey Senozhatsky
2019-11-13 15:32             ` Steven Rostedt
2019-11-11 19:47         ` Dmitry Safonov
2019-11-12  2:17           ` Sergey Senozhatsky
2019-11-12  2:40             ` Dmitry Safonov
2019-11-12  4:25               ` Sergey Senozhatsky
2019-11-13  2:41                 ` Dmitry Safonov
2019-11-13  2:51                   ` Sergey Senozhatsky
2019-11-13 15:39             ` Steven Rostedt
2019-11-15  3:36               ` Sergey Senozhatsky
2019-11-06  9:20 ` Peter Zijlstra
2019-11-06 16:27   ` Dmitry Safonov
2019-11-06 20:34     ` Peter Zijlstra
2019-11-06 23:25       ` Russell King - ARM Linux admin
2019-11-13 15:44         ` Steven Rostedt
2019-11-08 16:28       ` Dmitry Safonov
2019-11-08 17:30         ` Russell King - ARM Linux admin [this message]
2019-11-08 21:08           ` Dmitry Safonov
2019-11-13 15:41       ` Steven Rostedt

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191108173045.GY25745@shell.armlinux.org.uk \
    --to=linux@armlinux.org.uk \
    --cc=0x7f454c46@gmail.com \
    --cc=James.Bottomley@hansenpartnership.com \
    --cc=akpm@linux-foundation.org \
    --cc=anton.ivanov@cambridgegreys.com \
    --cc=aou@eecs.berkeley.edu \
    --cc=bcain@codeaurora.org \
    --cc=borntraeger@de.ibm.com \
    --cc=bp@alien8.de \
    --cc=bsegall@google.com \
    --cc=catalin.marinas@arm.com \
    --cc=chris@zankel.net \
    --cc=clang-built-linux@googlegroups.com \
    --cc=dalias@libc.org \
    --cc=daniel.thompson@linaro.org \
    --cc=davem@davemloft.net \
    --cc=deanbo422@gmail.com \
    --cc=deller@gmx.de \
    --cc=dianders@chromium.org \
    --cc=dietmar.eggemann@arm.com \
    --cc=dima@arista.com \
    --cc=fenghua.yu@intel.com \
    --cc=geert@linux-m68k.org \
    --cc=gor@linux.ibm.com \
    --cc=green.hu@gmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=guoren@kernel.org \
    --cc=gxt@pku.edu.cn \
    --cc=heiko.carstens@de.ibm.com \
    --cc=hpa@zytor.com \
    --cc=ink@jurassic.park.msu.ru \
    --cc=jacquiot.aurelien@gmail.com \
    --cc=jason.wessel@windriver.com \
    --cc=jcmvbkbc@gmail.com \
    --cc=jdike@addtoit.com \
    --cc=jhogan@kernel.org \
    --cc=jonas@southpole.se \
    --cc=jslaby@suse.com \
    --cc=juri.lelli@redhat.com \
    --cc=kgdb-bugreport@lists.sourceforge.net \
    --cc=len.brown@intel.com \
    --cc=lftan@altera.com \
    --cc=linux-alpha@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-c6x-dev@linux-c6x.org \
    --cc=linux-hexagon@vger.kernel.org \
    --cc=linux-ia64@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-m68k@lists.linux-m68k.org \
    --cc=linux-mips@vger.kernel.org \
    --cc=linux-parisc@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=linux-s390@vger.kernel.org \
    --cc=linux-sh@vger.kernel.org \
    --cc=linux-snps-arc@lists.infradead.org \
    --cc=linux-um@lists.infradead.org \
    --cc=linux-xtensa@linux-xtensa.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mattst88@gmail.com \
    --cc=mgorman@suse.de \
    --cc=mingo@kernel.org \
    --cc=mingo@redhat.com \
    --cc=monstr@monstr.eu \
    --cc=msalter@redhat.com \
    --cc=nios2-dev@lists.rocketboards.org \
    --cc=openrisc@lists.librecores.org \
    --cc=palmer@dabbelt.com \
    --cc=paul.walmsley@sifive.com \
    --cc=paulburton@kernel.org \
    --cc=paulus@samba.org \
    --cc=pavel@ucw.cz \
    --cc=penguin-kernel@i-love.sakura.ne.jp \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=ralf@linux-mips.org \
    --cc=richard@nod.at \
    --cc=rjw@rjwysocki.net \
    --cc=rostedt@goodmis.org \
    --cc=rth@twiddle.net \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=shorne@gmail.com \
    --cc=sparclinux@vger.kernel.org \
    --cc=stefan.kristiansson@saunalahti.fi \
    --cc=tglx@linutronix.de \
    --cc=tony.luck@intel.com \
    --cc=uclinux-h8-devel@lists.sourceforge.jp \
    --cc=vgupta@synopsys.com \
    --cc=vincent.guittot@linaro.org \
    --cc=will@kernel.org \
    --cc=x86@kernel.org \
    --cc=ysato@users.sourceforge.jp \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LinuxPPC-Dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linuxppc-dev/0 linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ https://lore.kernel.org/linuxppc-dev \
		linuxppc-dev@lists.ozlabs.org linuxppc-dev@ozlabs.org
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linuxppc-dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git