Messages in this thread | | | Subject | Re: [PATCH] mm: use in_atomic() in print_vma_addr() | From | "Yang Shi" <> | Date | Sat, 04 Nov 2017 02:16:45 +0800 |
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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I think the rule for in_atomic is obsolete in checkpatch.pl.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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