linux-kernel - Re: [PATCH 1/1] mm/page_alloc: add scheduling point to free_unref_page

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Date:   Wed, 9 Mar 2022 19:29:47 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     wangjianxing <wangjianxing@...ngson.cn>
Cc:     Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, vbabka@...e.cz
Subject: Re: [PATCH 1/1] mm/page_alloc: add scheduling point to
 free_unref_page_list

On Thu, 10 Mar 2022 10:48:41 +0800 wangjianxing <wangjianxing@...ngson.cn> wrote:

> spin_lock will preempt_disable(), interrupt context will 
> __irq_enter/local_bh_disable and also add preempt count with offset.
> 
> cond_resched check whether if preempt_count == 0 in first and won't 
> schedule in previous context.
> 
> Is this right?
> 
> 
> With another way, could we add some condition to avoid call cond_resched 
> in interrupt context or spin_lock()?
> 
> + if (preemptible())
> +       cond_resched();
> 

None of this works with CONFIG_PREEMPTION=n.