Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1497746

Re: [GIT PULL] trivial for 4.9

Show all headers | View raw

On Fri, Oct 07, 2016 at 04:09:51PM -0700, Tony Luck wrote:
> On Fri, Oct 7, 2016 at 4:01 PM, Tony Luck <tony.luck@gmail.com> wrote:
> > What if there isn't a "next printk" call for hours, or days?
> >
> > That poor little message without a "\n" will sit in the kernel buffers,
> > and the user who might want to see the message can't, until some
> > unrelated thing happens to print something.
> 
> Retracted ... I'm sure that at some point in the past it happened like
> that ... but
> I just retested on 4.8 and the first message (with no "\n") showed up on the
> serial port just fine without some other message to push it out. When the
> next message came along, a "\n" was auto-inserted.
> 

No there was a small window in time that it did just that. And it caused me a
day of debugging. My ftrace self tests at boot up do something like:

printk("testing X....");

if (test(X))
	printk(" PASSED\n");
else
	printk(" FAILED\n");


And with this new change, the "testing X..." never appeared, but it caused the
system to crash, It confused me because it crashed right after a:

testing Y.... PASSED

came out.

Thus I was debugging why Y failed caused the system crash even though it
reported a passing statement. The sad part was that my bug came in after this
updated to printk. So in bisecting I didn't notice. But what I did notice in
bisecting, was test X, and I tried that, and sure enough it crashed. Then
that's where I started looking at changes in printk.

I made a minor stink about it, and we converted the behavior back to where
kernel writes to printk would always go to the console.

-- Steve

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[GIT PULL] trivial for 4.9 Jiri Kosina <jikos@kernel.org> - 2016-10-07 11:00 +0200
  Re: [GIT PULL] trivial for 4.9 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-07 21:30 +0200
    Re: [GIT PULL] trivial for 4.9 Joe Perches <joe@perches.com> - 2016-10-07 22:10 +0200
      Re: [GIT PULL] trivial for 4.9 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-07 22:20 +0200
        Re: [GIT PULL] trivial for 4.9 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-07 22:30 +0200
          Re: [GIT PULL] trivial for 4.9 Joe Perches <joe@perches.com> - 2016-10-07 22:40 +0200
            Re: [GIT PULL] trivial for 4.9 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-07 23:10 +0200
              Re: [GIT PULL] trivial for 4.9 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-07 23:40 +0200
                Re: [GIT PULL] trivial for 4.9 Joe Perches <joe@perches.com> - 2016-10-08 09:40 +0200
                Re: [GIT PULL] trivial for 4.9 Joe Perches <joe@perches.com> - 2016-10-10 07:50 +0200
              Re: [GIT PULL] trivial for 4.9 Joe Perches <joe@perches.com> - 2016-10-07 23:50 +0200
                Re: [GIT PULL] trivial for 4.9 Tony Luck <tony.luck@gmail.com> - 2016-10-08 01:10 +0200
                Re: [GIT PULL] trivial for 4.9 Tony Luck <tony.luck@gmail.com> - 2016-10-08 01:20 +0200
                Re: [GIT PULL] trivial for 4.9 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-08 01:40 +0200
                Re: [GIT PULL] trivial for 4.9 Steven Rostedt <rostedt@goodmis.org> - 2016-10-08 15:30 +0200
        Re: [GIT PULL] trivial for 4.9 Joe Perches <joe@perches.com> - 2016-10-07 22:30 +0200

csiph-web