From: Waiman Long <longman@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Tim Chen <tim.c.chen@linux.intel.com>,
huang ying <huang.ying.caritas@gmail.com>
Subject: Re: [PATCH v3] locking/lock_events: Use this_cpu_add() when necessary
Date: Fri, 24 May 2019 15:05:18 -0400 [thread overview]
Message-ID: <0f8883ee-6e31-a1dd-a749-6d2ba07e758d@redhat.com> (raw)
In-Reply-To: <CAHk-=wgmB8BVrOZEqDysvC21MNmWcWXh1-DYzctsZYmZomkkog@mail.gmail.com>
On 5/24/19 3:00 PM, Linus Torvalds wrote:
> On Fri, May 24, 2019 at 11:54 AM Waiman Long <longman@redhat.com> wrote:
>> v2: Simplify the condition to just preempt or !preempt.
>> v3: Document the imprecise nature of the percpu count.
> My point was that if they are imprecise., then you shouldn't use CONFIG_PREEMPT.
>
> Because CONFIG_PREEMPT doesn't matter, and the count is imprecise with
> it or without it.
>
> So if they are imprecise, then what matters isn't whether the
> operation is atomic or not, and the real issue is avout whether it
> causes that "BUG: using __this_cpu_add() in preemptible" message.
>
> IOW, you should use the config option that matters and is relevant,
> namely CONFIG_DEBUG_PREEMPT.
Yes, that makes sense. I will update the patch again.
Thanks,
Longman
prev parent reply other threads:[~2019-05-24 19:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-24 18:53 [PATCH v3] locking/lock_events: Use this_cpu_add() when necessary Waiman Long
2019-05-24 19:00 ` Linus Torvalds
2019-05-24 19:05 ` Waiman Long [this message]
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