Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().

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To: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Fri, 23 Jun 2023 14:57:08 +0200
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>, Petr Mladek <pmladek@xxxxxxxx>, linux-mm@xxxxxxxxx, "Luis Claudio R. Goncalves" <lgoncalv@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>
In-reply-to: <20230623124416.M8fKvITC@linutronix.de>
References: <8b6d3f39-c573-ca2b-957b-8c48c2fa68ad@I-love.SAKURA.ne.jp> <d849fb4d-f259-2f24-fda3-4ea01869cb46@I-love.SAKURA.ne.jp> <ZJRWm0beSphxKsKA@alley> <ZJRjC0e_nmXQRirr@alley> <c70f4eae-4a81-4faa-c70c-b88cfda120f4@I-love.SAKURA.ne.jp> <20230623094544.RcLNdg6H@linutronix.de> <c35ddb2d-c541-d534-24e8-d03d373597d5@I-love.SAKURA.ne.jp> <20230623101111.7tuAg5p5@linutronix.de> <115cf90c-5bc5-d4b0-6489-d1ee5735194a@I-love.SAKURA.ne.jp> <20230623124416.M8fKvITC@linutronix.de>

On Fri 23-06-23 14:44:16, Sebastian Andrzej Siewior wrote:
[...]
> > Hmm, I feel worried that kmalloc(GFP_ATOMIC) from hard IRQ context
> > might sleep if RT...
> 
> Relax and don't worry. PREEMPT_RT does not allow (or has afaik) memory
> allocations from hard IRQ context (or preempt-disable sections).

Yeah, that would require something like GFP_LOCKLESS or change some of
the locking we have to raw spinlocks.

-- 
Michal Hocko
SUSE Labs

References:
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Tetsuo Handa
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Tetsuo Handa
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Petr Mladek
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Petr Mladek
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Tetsuo Handa
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Sebastian Andrzej Siewior
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Tetsuo Handa
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Sebastian Andrzej Siewior
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Tetsuo Handa
- Re: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
  - From: Sebastian Andrzej Siewior

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