From: "Yang Shi" <yang.s@alibaba-inc.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>,
mingo@redhat.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Joe Perches <joe@perches.com>
Subject: Re: [PATCH] mm: use in_atomic() in print_vma_addr()
Date: Sat, 04 Nov 2017 02:16:45 +0800 [thread overview]
Message-ID: <39320f9c-95fd-9cf6-6bd9-e31655168d43@alibaba-inc.com> (raw)
In-Reply-To: <20171103110245.7049460a05cc18c7e8a9feb2@linux-foundation.org>
On 11/3/17 11:02 AM, Andrew Morton wrote:
> On Fri, 03 Nov 2017 01:44:44 +0800 "Yang Shi" <yang.s@alibaba-inc.com> wrote:
>
>> I may not articulate it in the commit log
>
> You should have done so ;)
Yes, definitely. I could done it much better.
>
> Here's the changelog I ended up with:
>
> : From: "Yang Shi" <yang.s@alibaba-inc.com>
> : Subject: mm: use in_atomic() in print_vma_addr()
> :
> : 3e51f3c4004c9b ("sched/preempt: Remove PREEMPT_ACTIVE unmasking off
> : in_atomic()") uses in_atomic() just check the preempt count, so it is not
> : necessary to use preempt_count() in print_vma_addr() any more. Replace
> : preempt_count() to in_atomic() which is a generic API for checking atomic
> : context.
> :
> : in_atomic() is the preferred API for checking atomic context instead of
> : preempt_count() which should be used for retrieving the preemption count
> : value.
> :
> : If we go through the kernel code, almost everywhere "in_atomic" is used
> : for such use case already, except two places:
> :
> : - print_vma_addr()
> : - debug_smp_processor_id()
> :
> : Both came from Ingo long time ago before 3e51f3c4004c9b01 ("sched/preempt:
> : Remove PREEMPT_ACTIVE unmasking off in_atomic()"). But, after this commit
> : was merged, use in_atomic() to follow the convention.
> :
> : Link: http://lkml.kernel.org/r/1509572313-102989-1-git-send-email-yang.s@alibaba-inc.com
> : Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
> : Acked-by: Michal Hocko <mhocko@suse.com>
> : Cc: Frederic Weisbecker <fweisbec@gmail.com>
> : Cc: Ingo Molnar <mingo@elte.hu>
Thanks a lot for reworking the commit log.
>
>
>
> Also, checkpatch says
>
> WARNING: use of in_atomic() is incorrect outside core kernel code
> #43: FILE: mm/memory.c:4491:
> + if (in_atomic())
>
> I don't recall why we did that, but perhaps this should be revisited?
I think the rule for in_atomic is obsolete in checkpatch.pl. A quick
grep shows in_atomic() is used by arch, drivers, crypto, even though the
comment in include/linux/preempt.h says in_atomic() should be not used
by drivers.
However, the message could be ignored with --ignore=IN_ATOMIC. But, it
sounds better to fix the wrong rule and maybe even the comment in
include/linux/preempt.h since it sounds confusing.
Thanks,
Yang
>
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next prev parent reply other threads:[~2017-11-03 18:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-01 21:38 [PATCH] mm: use in_atomic() in print_vma_addr() Yang Shi
2017-11-02 7:57 ` Michal Hocko
2017-11-02 17:44 ` Yang Shi
2017-11-03 8:29 ` Michal Hocko
2017-11-03 18:02 ` Andrew Morton
2017-11-03 18:16 ` Yang Shi [this message]
2017-11-03 20:09 ` Bart Van Assche
2017-11-05 8:19 ` Michal Hocko
2017-11-06 10:05 ` Peter Zijlstra
2017-11-06 10:43 ` Michal Hocko
2017-11-06 10:56 ` Michal Hocko
2017-11-06 12:00 ` Peter Zijlstra
2017-11-06 12:12 ` Michal Hocko
2017-11-06 13:40 ` [PATCH] mm: do not rely on preempt_count in print_vma_addr (was: Re: [PATCH] mm: use in_atomic() in print_vma_addr()) Michal Hocko
2017-11-06 14:19 ` [PATCH] mm: do not rely on preempt_count in print_vma_addr Vlastimil Babka
2017-11-06 14:28 ` Michal Hocko
2017-11-06 16:16 ` Yang Shi
2017-11-06 16:24 ` Michal Hocko
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