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Commit 02cea395 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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genirq: Provide disable_hardirq() 



For things like netpoll there is a need to disable an interrupt from
atomic context. Currently netpoll uses disable_irq() which will
sleep-wait on threaded handlers and thus forced_irqthreads breaks
things.

Provide disable_hardirq(), which uses synchronize_hardirq() to only wait
for active hardirq handlers; also change synchronize_hardirq() to
return the status of threaded handlers.

This will allow one to try-disable an interrupt from atomic context, or
in case of request_threaded_irq() to only wait for the hardirq part.

Suggested-by: default avatarSabrina Dubroca <sd@queasysnail.net>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Miller <davem@davemloft.net>
Cc: Eyal Perry <eyalpe@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Quentin Lambert <lambert.quentin@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Link: http://lkml.kernel.org/r/20150205130623.GH5029@twins.programming.kicks-ass.net


[ Fixed typos and such. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4fe7ffb7

include/linux/hardirq.h

+1 −1
Original line number Diff line number Diff line
@@ -9,7 +9,7 @@ 




extern void synchronize_irq(unsigned int irq);

extern void synchronize_hardirq(unsigned int irq);

extern bool synchronize_hardirq(unsigned int irq);



#if defined(CONFIG_TINY_RCU)

include/linux/interrupt.h

+1 −0
Original line number Diff line number Diff line
@@ -184,6 +184,7 @@ extern void devm_free_irq(struct device *dev, unsigned int irq, void *dev_id); 
#endif



extern void disable_irq_nosync(unsigned int irq);

extern bool disable_hardirq(unsigned int irq);

extern void disable_irq(unsigned int irq);

extern void disable_percpu_irq(unsigned int irq);

extern void enable_irq(unsigned int irq);

kernel/irq/manage.c

+34 −2
Original line number Diff line number Diff line
@@ -68,14 +68,20 @@ static void __synchronize_hardirq(struct irq_desc *desc) 
 *	Do not use this for shutdown scenarios where you must be sure

 *	that all parts (hardirq and threaded handler) have completed.

 *

 *	Returns: false if a threaded handler is active.

 *

 *	This function may be called - with care - from IRQ context.

 */

void synchronize_hardirq(unsigned int irq)

bool synchronize_hardirq(unsigned int irq)

{

	struct irq_desc *desc = irq_to_desc(irq);



	if (desc)

	if (desc) {

		__synchronize_hardirq(desc);

		return !atomic_read(&desc->threads_active);

	}



	return true;

}

EXPORT_SYMBOL(synchronize_hardirq);
@@ -440,6 +446,32 @@ void disable_irq(unsigned int irq) 
}

EXPORT_SYMBOL(disable_irq);



/**

 *	disable_hardirq - disables an irq and waits for hardirq completion

 *	@irq: Interrupt to disable

 *

 *	Disable the selected interrupt line.  Enables and Disables are

 *	nested.

 *	This function waits for any pending hard IRQ handlers for this

 *	interrupt to complete before returning. If you use this function while

 *	holding a resource the hard IRQ handler may need you will deadlock.

 *

 *	When used to optimistically disable an interrupt from atomic context

 *	the return value must be checked.

 *

 *	Returns: false if a threaded handler is active.

 *

 *	This function may be called - with care - from IRQ context.

 */

bool disable_hardirq(unsigned int irq)

{

	if (!__disable_irq_nosync(irq))

		return synchronize_hardirq(irq);



	return false;

}

EXPORT_SYMBOL_GPL(disable_hardirq);



void __enable_irq(struct irq_desc *desc, unsigned int irq)

{

	switch (desc->depth) {