Re: [PATCH] pstore: Fix printing of duplicate boot messages to console

[Sai Prakash Ranjan]

On 2020-01-24 01:19, Stephen Boyd wrote:
> Quoting Sai Prakash Ranjan (2020-01-23 08:00:31)
> > Since commit f92b070f2dc8 ("printk: Do not miss new messages
> > when replaying the log"), CON_PRINTBUFFER flag causes the
> > duplicate boot messages to be printed on the console when
> > PSTORE_CONSOLE and earlycon (boot console) is enabled.
> > Pstore console registers to boot console when earlycon is
> > enabled during pstore_register_console as a part of ramoops
> > initialization in postcore_initcall and the printk core
> > checks for CON_PRINTBUFFER flag and replays the log buffer
> > to registered console (in this case pstore console which
> > just registered to boot console) causing duplicate messages
> > to be printed. Remove the CON_PRINTBUFFER flag from pstore
> > console since pstore is not concerned with the printing of
> > buffer to console but with writing of the buffer to the
> > backend.
> >
> > Console log with earlycon and pstore console enabled:
> >
> > [    0.008342] Console: colour dummy device 80x25
> > [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x51df805e]
> > ...
> > [    1.244049] hw-breakpoint: found 6 breakpoint and 4 watchpoint 
> > registers.
> > [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x51df805e]
> >
> > Fixes: f92b070f2dc8 ("printk: Do not miss new messages when replaying 
> > the log")
> > Reported-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> > Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > ---
>
> While I like the idea, it seems that this breaks console-ramoops by
> removing all the text that is printed in the kernel log before this
> console is registered. I reboot and see that
> /sys/fs/pstore/console-ramoops-1 starts like this now:
>
> 	localhost ~ # cat /sys/fs/pstore/console-ramoops-0
> 	[    0.943472] printk: console [pstore-1] enabled
>
> Maybe this console can be "special" and not require anything to be
> printed out to visible consoles but still get the entire log contents?
> Or we should just not worry about it.

Thanks for testing this out Stephen, I should have tested this some 
more.
Lets drop this patch.

-Sai

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