linux-kernel - Re: [PATCH v1 1/1] kernel.h: Split out panic and oops helpers

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Date:   Thu, 8 Apr 2021 14:45:12 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Joerg Roedel <jroedel@...e.de>, Wei Liu <wei.liu@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Mike Rapoport <rppt@...nel.org>,
        Corey Minyard <cminyard@...sta.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org,
        openipmi-developer@...ts.sourceforge.net,
        linux-remoteproc@...r.kernel.org, linux-arch@...r.kernel.org,
        kexec@...ts.infradead.org, rcu@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Corey Minyard <minyard@....org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Arnd Bergmann <arnd@...db.de>,
        Eric Biederman <ebiederm@...ssion.com>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>
Subject: Re: [PATCH v1 1/1] kernel.h: Split out panic and oops helpers

On 06/04/2021 15.31, Andy Shevchenko wrote:
> kernel.h is being used as a dump for all kinds of stuff for a long time.
> Here is the attempt to start cleaning it up by splitting out panic and
> oops helpers.

Yay.

Acked-by: Rasmus Villemoes <linux@...musvillemoes.dk>

> At the same time convert users in header and lib folder to use new header.
> Though for time being include new header back to kernel.h to avoid twisted
> indirected includes for existing users.

I think it would be good to have some place to note that "This #include
is just for backwards compatibility, it will go away RealSoonNow, so if
you rely on something from linux/panic.h, include that explicitly
yourself TYVM. And if you're looking for a janitorial task, write a
script to check that every file that uses some identifier defined in
panic.h actually includes that file. When all offenders are found and
dealt with, remove the #include and this note.".

> +
> +struct taint_flag {
> +	char c_true;	/* character printed when tainted */
> +	char c_false;	/* character printed when not tainted */
> +	bool module;	/* also show as a per-module taint flag */
> +};
> +
> +extern const struct taint_flag taint_flags[TAINT_FLAGS_COUNT];

While you're doing this, nothing outside of kernel/panic.c cares about
the definition of struct taint_flag or use the taint_flags array, so
could you make the definition private to that file and make the array
static? (Another patch, of course.)

> +enum lockdep_ok {
> +	LOCKDEP_STILL_OK,
> +	LOCKDEP_NOW_UNRELIABLE,
> +};
> +
> +extern const char *print_tainted(void);
> +extern void add_taint(unsigned flag, enum lockdep_ok);
> +extern int test_taint(unsigned flag);
> +extern unsigned long get_taint(void);

I know you're just moving code, but it would be a nice opportunity to
drop the redundant externs.

Rasmus