From: "Yang Shi" <yang.s@alibaba-inc.com>
To: Michal Hocko <mhocko@kernel.org>, mingo@redhat.com
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: use in_atomic() in print_vma_addr()
Date: Fri, 03 Nov 2017 01:44:44 +0800 [thread overview]
Message-ID: <ace5b078-652b-cbc0-176a-25f69612f7fa@alibaba-inc.com> (raw)
In-Reply-To: <20171102075744.whhxjmqbdkfaxghd@dhcp22.suse.cz>
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
>
next prev parent reply other threads:[~2017-11-02 17:45 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 [this message]
2017-11-03 8:29 ` Michal Hocko
2017-11-03 18:02 ` Andrew Morton
2017-11-03 18:16 ` Yang Shi
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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