[PATCH 4.4-rc5 v22 2/4] irqchip: gic: Make gic_raise_softirq FIQ-safe

[Marc Zyngier]

On 20/12/15 20:52, Daniel Thompson wrote:
> It is currently possible for FIQ handlers to re-enter gic_raise_softirq()
> and lock up.
> 
>     	gic_raise_softirq()
> 	   lock(x);
> -~-> FIQ
>         handle_fiq()
> 	   gic_raise_softirq()
> 	      lock(x);		<-- Lockup
> 
> arch/arm/ uses IPIs to implement arch_irq_work_raise(), thus this issue
> renders it difficult for FIQ handlers to safely defer work to less
> restrictive calling contexts.
> 
> This patch fixes the problem by converting the cpu_map_migration_lock
> into a rwlock making it safe to re-enter the function.
> 
> Note that having made it safe to re-enter gic_raise_softirq() we no
> longer need to mask interrupts during gic_raise_softirq() because the
> b.L migration is always performed from task context.
> 
> Signed-off-by: Daniel Thompson <daniel.thompson at linaro.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Jason Cooper <jason at lakedaemon.net>
> Cc: Russell King <linux at arm.linux.org.uk>
> Cc: Marc Zyngier <marc.zyngier at arm.com>
> Acked-by: Nicolas Pitre <nicolas.pitre at linaro.org>

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

	M.
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