linux-kernel - Re: [PATCH] kernel/locking: make __down

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Message-ID: <YJwn7qb3/ekFBWDF@gmail.com>
Date:   Wed, 12 May 2021 21:09:34 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] kernel/locking: make __down_common use flags previously
 saved


* Hyeonggon Yoo <42.hyeyoo@...il.com> wrote:

> down, down_interruptible, down_killable, and down_timeout
> call raw_spin_lock_irqsave that saves current status to flags.
> 
> but in __down_common, that is called by functions above, calls
> raw_spin_lock_irq and raw_spin_unlock_irq regardless of flags previously saved.

Yes, this is intentional, because if we get into __down_common() we have to 
schedule, so we have to enable interrupts.

> this mismatch can potentially cause problem.

What problems?

Thanks,

	Ingo