Re: [RFC PATCH] scripts: checkpatch.pl: remove obsolete in_atomic rule

From: Joe Perches
Date: Fri Nov 03 2017 - 15:41:40 EST


On Sat, 2017-11-04 at 03:08 +0800, Yang Shi wrote:
> checkpatch.pl still reports the below in_atomic warning:
>
> WARNING: use of in_atomic() is incorrect outside core kernel code
> + if (in_atomic())
>
> But, in_atomic() has been used outside kernel dir for a long time, and
> even drivers. So, remove the obsolete rule even though they can be
> ignored.

Removing in_atomic() from checkpatch does not make sense
without also updating include/linux/preempt.h

Jonathon Corbet added this comment in

commit 8c703d35fa91911dd92a18c31a718853f483ad80
Author: Jonathan Corbet <corbet@xxxxxxx>
Date: Fri Mar 28 14:15:49 2008 -0700

in_atomic(): document why it is unsuitable for general use

Discourage people from inappropriately using in_atomic()

Signed-off-by: Jonathan Corbet <corbet@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/hardirq.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 49829988bfa0..897f723bd222 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -72,6 +72,13 @@
#define in_softirq() (softirq_count())
#define in_interrupt() (irq_count())

+/*
+ * Are we running in atomic context? WARNING: this macro cannot
+ * always detect atomic context; in particular, it cannot know about
+ * held spinlocks in non-preemptible kernels. Thus it should not be
+ * used in the general case to determine whether sleeping is possible.
+ * Do not use in_atomic() in driver code.
+ */

Maybe he remembers why...

> Signed-off-by: Yang Shi <yang.s@xxxxxxxxxxxxxxx>
> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> Not sure if removing the obsolete rule is preferred by checkpatch.pl, anyway
> it sounds not make sense to keep invalid rule.
>
> scripts/checkpatch.pl | 11 -----------
> 1 file changed, 11 deletions(-)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 8b80bac..e8cf94f 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6231,17 +6231,6 @@ sub process {
> "Using $1 should generally have parentheses around the comparison\n" . $herecurr);
> }
>
> -# whine mightly about in_atomic
> - if ($line =~ /\bin_atomic\s*\(/) {
> - if ($realfile =~ m@^drivers/@) {
> - ERROR("IN_ATOMIC",
> - "do not use in_atomic in drivers\n" . $herecurr);
> - } elsif ($realfile !~ m@^kernel/@) {
> - WARN("IN_ATOMIC",
> - "use of in_atomic() is incorrect outside core kernel code\n" . $herecurr);
> - }
> - }
> -
> # whine about ACCESS_ONCE
> if ($^V && $^V ge 5.10.0 &&
> $line =~ /\bACCESS_ONCE\s*$balanced_parens\s*(=(?!=))?\s*($FuncArg)?/) {