On 11/3/17 11:02 AM, Andrew Morton wrote:
On Fri, 03 Nov 2017 01:44:44 +0800 "Yang Shi" <yang.s@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
: 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@xxxxxxxxxxxxxxx
: Signed-off-by: Yang Shi <yang.s@xxxxxxxxxxxxxxx>
: Acked-by: Michal Hocko <mhocko@xxxxxxxx>
: Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
: Cc: Ingo Molnar <mingo@xxxxxxx>
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I think the rule for in_atomic is obsolete in checkpatch.pl.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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