linux-kernel - Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline

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Date:	Thu, 3 Apr 2014 13:38:29 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mateusz Guzik <mguzik@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Mel Gorman <mgorman@...e.de>,
	Kay Sievers <kay@...y.org>
Subject: Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline


* Borislav Petkov <bp@...en8.de> wrote:

> On Wed, Apr 02, 2014 at 06:47:57PM -0700, Linus Torvalds wrote:
> > Whether it actually fixes the problem that Borislav had is
> > questionable, of course. For all I know, systemd debug mode generates
> > so much data in *other* ways and then causes feedback loops with
> > the kernel debugging that this patch is totally immaterial, and
> > dmesg was never the main issue. But unlike the "hide 'debug' from
> > /proc/cmdline", I think this patch at least _conceptually_ makes a lot
> > of sense, even if systemd gets fixed, so ...
> >
> > Borislav?
> 
> Yes, ratelimiting makes the box actually boot all the way. Here's how it
> looks like:
> 
> ^MLoading Linux 3.12.16-boris-00441-g60dc93e99a75-dirty ...
> ^MLoading initial ramdisk ...
> ^M[    0.000000] Initializing cgroup subsys cpuset
> [    0.000000] Initializing cgroup subsys cpu
> [    0.000000] Initializing cgroup subsys cpuacct
> [    0.000000] Linux version 3.12.16-boris-00441-g60dc93e99a75-dirty (gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux) ) #11 SMP Thu Apr 3 10:19:49 CEST 2014
> [    0.000000] Command line: BOOT_IMAGE=/@...ot/vmlinuz-3.12.16-boris-00441-g60dc93e99a75-dirty root=UUID=5f1a28cf-d910-
> 4ed0-85ac-0113d43e553f rootflags=subvol=@ resume=/dev/disk/by-uuid/45671aef-cef3-4fcd-9087-7d4f3f81aa70 splash=off showo
> pts crashkernel=256M-:128M pci=hpiosize=0 pci=hpmemsize=4m pciehp.pciehp_force=1 notsc mem=0x40000000000 loop.max_loop=6
> 4 log_buf_len=16M console=tty0 console=ttyS0,38400n8 ignore_loglevel debug
> 								     ^^^^^
> 
> We haz the "debug" thing on.
> 
> ...
> 
> Here we go:
> 
> [   50.636000] be2net 0000:db:00.0: irq 102 for MSI/MSI-X
> [   50.636000] be2net 0000:db:00.0: irq 103 for MSI/MSI-X
> [   50.636000] be2net 0000:db:00.0: irq 104 for MSI/MSI-X
> [   50.636000] be2net 0000:db:00.0: enabled 4 MSI-x vector(s) for NIC
> [   50.896000] systemd: 1008 callbacks suppressed
> 			^^^^
> 
> [   50.896000] systemd[1]: Started Show Plymouth Boot Screen.
> [   50.896000] systemd[1]: Got SIGCHLD for process 1192 (swapon)
> [   50.896000] systemd[1]: Child 1192 died (code=exited, status=0/SUCCESS)
> [   50.896000] systemd[1]: Child 1192 belongs to dev-disk-by\x2duuid-45671aef\x2dcef3\x2d4fcd\x2d9087\x2d7d4f3f81aa70.swap
> [   50.896000] systemd[1]: dev-disk-by\x2duuid-45671aef\x2dcef3\x2d4fcd\x2d9087\x2d7d4f3f81aa70.swap swap process exited, code=exited status=0
> [   50.896000] systemd[1]: dev-disk-by\x2duuid-45671aef\x2dcef3\x2d4fcd\x2d9087\x2d7d4f3f81aa70.swap changed activating -> active
> [   50.896000] systemd[1]: Job dev-disk-by\x2duuid-45671aef\x2dcef3\x2d4fcd\x2d9087\x2d7d4f3f81aa70.swap/start finished, result=done
> 
> ...
> 
> [   57.988000] scsi2 : Emulex 10Gbe open-iscsi Initiator Driver
> [   63.028000] be2iscsi 0000:db:00.3: irq 117 for MSI/MSI-X
> [   63.044000] be2iscsi 0000:db:00.3: irq 118 for MSI/MSI-X
> [   63.064000] be2iscsi 0000:db:00.3: irq 119 for MSI/MSI-X
> [   63.080000] be2iscsi 0000:db:00.3: irq 120 for MSI/MSI-X
> [   63.100000] be2iscsi 0000:db:00.3: irq 121 for MSI/MSI-X
> [   63.116000] be2iscsi 0000:db:00.3: irq 122 for MSI/MSI-X
> [   63.132000] be2iscsi 0000:db:00.3: irq 123 for MSI/MSI-X
> [   63.152000] be2iscsi 0000:db:00.3: irq 124 for MSI/MSI-X
> [   63.572000] scsi host2: BC_373 : Link Down on Port 1
> [   63.588000] scsi host2: BM_4336 : No boot session
> [   63.656000] systemd: 11828 callbacks suppressed
> 			^^^^^
> 
> We luvz to talk a lot of crap, don't we.

When I suggested that systemd should reuse the tracing and perf ring 
buffer infrastructure instead of cluttering the syslog it was 
handwaved away...

But at least there's an upside for me: I don't have to deal with the 
systemd maintainers' excessively passive-aggressive behavior ;-)

Thanks,

	Ingo
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