linux-kernel - Re: [PATCH 2/2] s390: convert to GENERIC

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Date:   Mon, 3 Aug 2020 20:44:28 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Sven Schnelle <svens@...ux.ibm.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH 2/2] s390: convert to GENERIC_VDSO

On Mon, Aug 03, 2020 at 06:05:24PM +0200, Thomas Gleixner wrote:
> +/**
> + * vdso_update_begin - Start of a VDSO update section
> + *
> + * Allows architecture code to safely update the architecture specific VDSO
> + * data.
> + */
> +void vdso_update_begin(void)
> +{
> +	struct vdso_data *vdata = __arch_get_k_vdso_data();
> +
> +	raw_spin_lock(&timekeeper_lock);
> +	vdso_write_begin(vdata);
> +}

I would assume that this only works if vdso_update_begin() is called
with irqs disabled, otherwise it could deadlock, no?

Maybe something like:

void vdso_update_begin(unsigned long *flags)
{
	struct vdso_data *vdata = __arch_get_k_vdso_data();

	raw_spin_lock_irqsave(&timekeeper_lock, *flags);
	vdso_write_begin(vdata);
}

void vdso_update_end(unsigned long *flags)
{
	struct vdso_data *vdata = __arch_get_k_vdso_data();

	vdso_write_end(vdata);
	__arch_sync_vdso_data(vdata);
	raw_spin_unlock_irqrestore(&timekeeper_lock, *flags);
}

? Just wondering.