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Message-ID: <Y4dt3IMYKYnufHg5@alley>
Date: Wed, 30 Nov 2022 15:51:08 +0100
From: Petr Mladek <pmladek@...e.com>
To: Joe Perches <joe@...ches.com>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
linux-pm@...r.kernel.org,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Andy Whitcroft <apw@...onical.com>,
linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
Dwaipayan Ray <dwaipayanray1@...il.com>,
Lukas Bulwahn <lukas.bulwahn@...il.com>
Subject: Re: [PATCH v2 2/3] checkpatch: handle new pr_<level>_cont macros
On Fri 2022-11-25 12:17:05, Joe Perches wrote:
> On Fri, 2022-11-25 at 20:09 +0100, Thomas Weißschuh wrote:
> > These new macros from include/linux/printk.h replace the usage of plain
> > pr_cont().
> []
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -590,7 +590,7 @@ our $zero_initializer = qr{(?:(?:0[xX])?0+$Int_type?|NULL|false)\b};
> > +# check for logging continuations without explicit level
> > + if ($line =~ /\bpr_cont\s*\(/) {
> > + WARN("LOGGING_CONTINUATION_WITHOUT_LEVEL",
> > + "Avoid logging continuation without level\n" . $herecurr);
> > + }
> > +
>
> Not so sure about this one.
>
> I think relatively few situations are going to require interleaving avoidance.
Well, the problem is generic and any pr_cont() is affected except for
NMI context on single CPU system.
I though about a generic solution. We could store the last used printk
log level per-process and per-CPU context. But it does not solve
the situation when an unrelated printk() is printed by a nested
function.
It is exactly the case with try_to_freeze_tasks() in the 3rd patch.
Simplified code:
int freeze_processes(void)
{
pr_info("Freezing user space processes ... ");
try_to_freeze_tasks(true);
pr_info_cont("done.");
}
, where
static int try_to_freeze_tasks(bool user_only)
{
[...]
if (todo) {
pr_err("Freezing of tasks %s after %d.%03d seconds "
[...]
}
I would personally add this check into checkpatch.pl. It might help
to make people aware about that pr_cont() is just the best effort.
Best Regards,
Petr
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