Re: [GIT pull] printk updates for 4.15

From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salyzyn <salyzyn@android.com>,
	Petr Mladek <pmladek@suse.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Prarit Bhargava <prarit@redhat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [GIT pull] printk updates for 4.15
Date: Wed, 15 Nov 2017 00:04:18 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1711150001190.2221@nanos> (raw)
In-Reply-To: <CA+55aFzM+UK=X163YHqAjYnt2ne0oBq9AT1+Ct8XoxbwOmH4rA@mail.gmail.com>

On Tue, 14 Nov 2017, Linus Torvalds wrote:

> On Tue, Nov 14, 2017 at 2:50 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > Something like the untested patch below should do the storage and converts
> > the primary timestamp from local_clock() to clock monotonic.
> 
> This  may work.
> 
> > -       u64 ts_nsec;            /* timestamp in nanoseconds */
> > +       /* Timestamps in nanoseconds */
> > +       union {
> > +               u64                     ts_nsec;
> > +               struct timestamps       ts;
> > +       };
> 
> But I'd skip the union, and just search-and-replace the ts_nsec ->
> ts.mono. You did that in at least one place anyway.
> 
> Because as it is, that's just too subtle and hard to read. Don't make
> it worse by having a magical "ts_nsec is also ts.mono, but you have to
> look in two different files to see that.
> 
> That file is messy enough as-is.

True. I already replaced all of them except this one:

@@ -1022,6 +1026,7 @@ void log_buf_vmcoreinfo_setup(void)
         */
        VMCOREINFO_STRUCT_SIZE(printk_log);
        VMCOREINFO_OFFSET(printk_log, ts_nsec);
+       VMCOREINFO_OFFSET(printk_log, ts);
        VMCOREINFO_OFFSET(printk_log, len);
        VMCOREINFO_OFFSET(printk_log, text_len);
        VMCOREINFO_OFFSET(printk_log, dict_len);

If I remove ts_nsec completely, then the VMCORE info changes and that would
break existing tools because they search for ts_nsec and fail....

Thanks,

	tglx
