Re: [PATCH 4.4-rc5 v22 1/4] irqchip: gic: Optimize locking in gic_raise_softirq

[Marc Zyngier <marc.zyngier@arm.com>]

On 20/12/15 20:52, Daniel Thompson wrote:
> Currently gic_raise_softirq() is locked using irq_controller_lock.
> This lock is primarily used to make register read-modify-write sequences
> atomic but gic_raise_softirq() uses it instead to ensure that the
> big.LITTLE migration logic can figure out when it is safe to migrate
> interrupts between physical cores.
> 
> This is sub-optimal in closely related ways:
> 
> 1. No locking at all is required on systems where the b.L switcher is
>    not configured.
> 
> 2. Finer grain locking can be used on systems where the b.L switcher is
>    present.
> 
> This patch resolves both of the above by introducing a separate finer
> grain lock and providing conditionally compiled inlines to lock/unlock
> it.
> 
> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jason Cooper <jason@lakedaemon.net>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

	M.
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