Re: [PATCH] mm: use in_atomic() in print_vma_addr()

[Andrew Morton <akpm@linux-foundation.org>]

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 ;)

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>



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?

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