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From: Dmitry Vyukov <dvyukov@google.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Marco Elver <elver@google.com>,
	Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 4/5] kcov: Avoid enable+disable interrupts if !in_task().
Date: Fri, 17 Sep 2021 16:50:37 +0200	[thread overview]
Message-ID: <CACT4Y+aCm60gfP9uyEdb-KKaikGGXkrcY8FXhESnPyO_cWBw4A@mail.gmail.com> (raw)
In-Reply-To: <20210830172627.267989-5-bigeasy@linutronix.de>

On Mon, 30 Aug 2021 at 19:26, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> kcov_remote_start() may need to allocate memory in the in_task() case
> (otherwise per-CPU memory has been pre-allocated) and therefore requires
> enabled interrupts.
> The interrupts are enabled before checking if the allocation is required
> so if no allocation is required then the interrupts are needlessly
> enabled and disabled again.
>
> Enable interrupts only if memory allocation is performed.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Acked-by: Dmitry Vyukov <dvyukov@google.com>

> ---
>  kernel/kcov.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 4f910231d99a2..620dc4ffeb685 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -869,19 +869,19 @@ void kcov_remote_start(u64 handle)
>                 size = CONFIG_KCOV_IRQ_AREA_SIZE;
>                 area = this_cpu_ptr(&kcov_percpu_data)->irq_area;
>         }
> -       spin_unlock_irqrestore(&kcov_remote_lock, flags);
> +       spin_unlock(&kcov_remote_lock);
>
>         /* Can only happen when in_task(). */
>         if (!area) {
> +               local_irqrestore(flags);
>                 area = vmalloc(size * sizeof(unsigned long));
>                 if (!area) {
>                         kcov_put(kcov);
>                         return;
>                 }
> +               local_irq_save(flags);
>         }
>
> -       local_irq_save(flags);
> -
>         /* Reset coverage size. */
>         *(u64 *)area = 0;
>
> --
> 2.33.0
>

  reply	other threads:[~2021-09-17 14:50 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-30 17:26 [PATCH 0/5] kcov: PREEMPT_RT fixup + misc Sebastian Andrzej Siewior
2021-08-30 17:26 ` [PATCH 1/5] Documentation/kcov: Include types.h in the example Sebastian Andrzej Siewior
2021-09-17 14:34   ` Dmitry Vyukov
2021-08-30 17:26 ` [PATCH 2/5] Documentation/kcov: Define `ip' " Sebastian Andrzej Siewior
2021-09-17 14:37   ` Dmitry Vyukov
2021-08-30 17:26 ` [PATCH 3/5] kcov: Allocate per-CPU memory on the relevant node Sebastian Andrzej Siewior
2021-09-17 14:38   ` Dmitry Vyukov
2021-08-30 17:26 ` [PATCH 4/5] kcov: Avoid enable+disable interrupts if !in_task() Sebastian Andrzej Siewior
2021-09-17 14:50   ` Dmitry Vyukov [this message]
2021-08-30 17:26 ` [PATCH 5/5] kcov: Replace local_irq_save() with a local_lock_t Sebastian Andrzej Siewior
2021-09-17 14:58   ` Dmitry Vyukov
2021-09-06 16:13 ` [PATCH 0/5] kcov: PREEMPT_RT fixup + misc Marco Elver
2021-09-06 16:28   ` Sebastian Andrzej Siewior
2021-09-20  9:26     ` Marco Elver
2021-09-20  9:50       ` Sebastian Andrzej Siewior

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