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From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 15 Feb 2024 06:36:50 +0900
Message-ID: <CAK7LNARJERFRF=EM3RKL5jMgLbq0H1Op7FSRLJaVjrcR_nv0NA@mail.gmail.com>
Subject: Re: [PATCH v5 1/3] printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL
 is enabled
To: Yoann Congal <yoann.congal@smile.fr>
Cc: linux-fsdevel@vger.kernel.org, linux-kbuild@vger.kernel.org, 
	linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, x86@kernel.org, 
	=?UTF-8?Q?Andr=C3=A9_Almeida?= <andrealmeid@igalia.com>, 
	Borislav Petkov <bp@alien8.de>, Darren Hart <dvhart@infradead.org>, 
	Dave Hansen <dave.hansen@linux.intel.com>, Davidlohr Bueso <dave@stgolabs.net>, 
	Geert Uytterhoeven <geert@linux-m68k.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
	"H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, Jiri Slaby <jirislaby@kernel.org>, 
	John Ogness <john.ogness@linutronix.de>, Josh Triplett <josh@joshtriplett.org>, 
	Matthew Wilcox <willy@infradead.org>, Peter Zijlstra <peterz@infradead.org>, 
	Petr Mladek <pmladek@suse.com>, Sergey Senozhatsky <senozhatsky@chromium.org>, 
	Steven Rostedt <rostedt@goodmis.org>, Thomas Gleixner <tglx@linutronix.de>, 
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>, Vegard Nossum <vegard.nossum@oracle.com>
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On Tue, Feb 13, 2024 at 4:01=E2=80=AFAM Yoann Congal <yoann.congal@smile.fr=
> wrote:
>
>
>
> Le 11/02/2024 =C3=A0 00:41, Masahiro Yamada a =C3=A9crit :
> > On Thu, Feb 8, 2024 at 2:10=E2=80=AFAM Yoann Congal <yoann.congal@smile=
fr> wrote:
> >>
> >> LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL:
> >>   config LOG_CPU_MAX_BUF_SHIFT
> >>         default 12 if !BASE_SMALL
> >>         default 0 if BASE_SMALL
> >> But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always
> >> evaluated to true whatever is the value of BASE_SMALL.
> >>
> >> This patch fixes this by using the correct conditional operator for in=
t
> >> type : BASE_SMALL !=3D 0.
> >>
> >> Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D12 to
> >> CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D0 for BASE_SMALL defconfigs, but that w=
ill
> >> not be a big impact due to this code in kernel/printk/printk.c:
> >>   /* by default this will only continue through for large > 64 CPUs */
> >>   if (cpu_extra <=3D __LOG_BUF_LEN / 2)
> >>           return;
> >> Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite
> >> rare.
> >>
> >> John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote:
> >>> For printk this will mean that BASE_SMALL systems were probably
> >>> previously allocating/using the dynamic ringbuffer and now they will
> >>> just continue to use the static ringbuffer. Which is fine and saves
> >>> memory (as it should).
> >>
> >> Petr Mladek <pmladek@suse.com> (printk maintainer) wrote:
> >>> More precisely, it allocated the buffer dynamically when the sum
> >>> of per-CPU-extra space exceeded half of the default static ring
> >>> buffer. This happened for systems with more than 64 CPUs with
> >>> the default config values.
> >>
> >> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> >> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> >> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=3D2XUAHascps7=
6YQac6rdnQGhc8nop_Q@mail.gmail.com/
> >> Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
> >> Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29a=
da@oracle.com/
> >> Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")
> >>
> >
> >
> >
> > All the Reviewed-by tags are dropped every time, annoyingly.
>
> Hi!
>
> Was I supposed to gather these tags from patch version N to patch version=
 N+1?
> In that case, I'm sorry, I did not know that :-/
> Patch 1/3 is exactly the same but patch 2/3 is equivalent but different. =
Is there a rule written somewhere about when carrying the tags across revis=
ion and when not? (I could not find it)


I do not know any written rules either.


In my experience, people carry tags
when changes since the previous version are small.


--=20
Best Regards
Masahiro Yamada