Messages in this thread Patch in this message | | | Subject | Re: [PATCH] mm: use in_atomic() in print_vma_addr() | From | "Yang Shi" <> | Date | Fri, 03 Nov 2017 01:44:44 +0800 |
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On 11/2/17 12:57 AM, Michal Hocko wrote: > On Thu 02-11-17 05:38:33, Yang Shi wrote: >> commit 3e51f3c4004c9b01f66da03214a3e206f5ed627b >> ("sched/preempt: Remove PREEMPT_ACTIVE unmasking off in_atomic()") makes >> 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. > > But why? Is there some general work to get rid of the direct preempt_count > usage outside of the generic API?
I may not articulate it in the commit log, I would say "in_atomic" is *preferred* API for checking atomic context instead of preempt_count() which should be used for retrieving the preemption count value.
I would say there is not such general elimination work undergoing right now, but 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 commit 3e51f3c4004c9b01f66da03214a3e206f5ed627b ("sched/preempt: Remove PREEMPT_ACTIVE unmasking off in_atomic()"). But, after this commit was merged, I don't see why *not* use in_atomic() to follow the convention.
Thanks, Yang
> >> Signed-off-by: Yang Shi <yang.s@alibaba-inc.com> >> --- >> mm/memory.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index a728bed..19b684e 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -4460,7 +4460,7 @@ void print_vma_addr(char *prefix, unsigned long ip) >> * Do not print if we are in atomic >> * contexts (in exception stacks, etc.): >> */ >> - if (preempt_count()) >> + if (in_atomic()) >> return; >> >> down_read(&mm->mmap_sem); >> -- >> 1.8.3.1 >
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