linux-kernel - Re: [GIT pull] printk updates for 4.15

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Date:   Wed, 15 Nov 2017 00:04:18 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Mark Salyzyn <salyzyn@...roid.com>, Petr Mladek <pmladek@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [GIT pull] printk updates for 4.15

On Tue, 14 Nov 2017, Linus Torvalds wrote:

> On Tue, Nov 14, 2017 at 2:50 PM, Thomas Gleixner <tglx@...utronix.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