Re: [PATCH RT] mm: Don't warn about atomic memory allocations during suspend

From: Liwei Song <liwei.song@windriver.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt <linux-rt-users@vger.kernel.org>,
	Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH RT] mm: Don't warn about atomic memory allocations during suspend
Date: Tue, 5 May 2020 11:59:29 +0800	[thread overview]
Message-ID: <a24d2165-a2d2-b63e-36a0-7dc9d6a0cf06@windriver.com> (raw)
In-Reply-To: <20200504145325.3rjc3iskg2coejje@linutronix.de>

On 5/4/20 22:53, Sebastian Andrzej Siewior wrote:
> From: Liwei Song <liwei.song@windriver.com>
> 
> The ACPI code allocates larger amount of memory during resume. This
> triggers a warning because the allocation happens with disabled
> interrupts.
> At this stage only one CPU is active so there should be no lock
> contention. If SLUB needs to call into the buddy allocator for more
> memory then it should not enable interrupts.
> 
> Limit the check to system state with more CPUs and scheduling and only
> enable interrupts in SLUB at this stage.
> 
> Signed-off-by: Liwei Song <liwei.song@windriver.com>
> [bigeasy: commit description, allocate_slab() hunk]
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> 
> Are you okay with this Liwei?

Yes, I'm fine with this, thanks for your help.

Liwei.

> 
>  mm/slub.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 15c194ff16e6e..6ea1057edf1ab 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1655,7 +1655,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
>  		enableirqs = true;
>  
>  #ifdef CONFIG_PREEMPT_RT
> -	if (system_state > SYSTEM_BOOTING)
> +	if (system_state > SYSTEM_BOOTING && system_state < SYSTEM_SUSPEND)
>  		enableirqs = true;
>  #endif
>  	if (enableirqs)
> @@ -2771,7 +2771,8 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
>  	unsigned long tid;
>  
>  	if (IS_ENABLED(CONFIG_PREEMPT_RT) && IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP))
> -		WARN_ON_ONCE(!preemptible() && system_state >= SYSTEM_SCHEDULING);
> +		WARN_ON_ONCE(!preemptible() &&
> +			     (system_state > SYSTEM_BOOTING && system_state < SYSTEM_SUSPEND));
>  
>  	s = slab_pre_alloc_hook(s, gfpflags);
>  	if (!s)
> @@ -3236,7 +3237,8 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
>  	int i;
>  
>  	if (IS_ENABLED(CONFIG_PREEMPT_RT) && IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP))
> -		WARN_ON_ONCE(!preemptible() && system_state >= SYSTEM_SCHEDULING);
> +		WARN_ON_ONCE(!preemptible() &&
> +			     (system_state > SYSTEM_BOOTING && system_state < SYSTEM_SUSPEND));
>  
>  	/* memcg and kmem_cache debug support */
>  	s = slab_pre_alloc_hook(s, flags);
> 