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SubjectRe: [GIT pull] printk updates for 4.15
On Tue, 14 Nov 2017, Linus Torvalds wrote:
> On Tue, Nov 14, 2017 at 3:04 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > 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....
>
> Dear god, that's nasty.
>
> I agree that the vmcore info name probably needs to be retained, but
> maybe we could just do that with
>
> #define VMCOREINFO_FIELD_AND_OFFSET(name, field, offset) \
> vmcoreinfo_append_str("OFFSET(%s.%s)=%lu\n", name, field, offset)
>
> and then do
>
> #define VMCOREINFO_OFFSET(name, field) \
> VMCOREINFO_FIELD_AND_OFFSET(#name, #field, \
> (unsigned long)offsetof(struct name, offset))
>
> and for that ts_nsec you can then do
>
> /* ts.mono used to be called "ts_nsec" */
> VMCOREINFO_FIELD_AND_OFFSET("printk_log", "ts_nsec",
> (unsigned long)offsetof(struct printk_log, ts.mono))
>
> or something.
>
> And I may obviously have messed that all up, I wrote it all in the
> email client, so it's more pseudo-code than anything else.
>
> But it looks pretty straight-forward conceptually, and would make it
> pretty clear what is going on, no?

That should work. I'll try that tomorrow with brain awake.

Thanks,

tglx

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