Commit 753649db authored Mar 31, 2010 by Thomas Gleixner

genirq: Force MSI irq handlers to run with interrupts disabled



Network folks reported that directing all MSI-X vectors of their multi
queue NICs to a single core can cause interrupt stack overflows when
enough interrupts fire at the same time.

This is caused by the fact that we run interrupt handlers by default
with interrupts enabled unless the driver reuqests the interrupt with
the IRQF_DISABLED set. The NIC handlers do not set this flag, so
simultaneous interrupts can nest unlimited and cause the stack
overflow.

The only safe counter measure is to run the interrupt handlers with
interrupts disabled. We can't switch to this mode in general right
now, but it is safe to do so for MSI interrupts.

Force IRQF_DISABLED for MSI interrupt handlers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@osdl.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Miller <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: stable@kernel.org

parent 2eaa9cfd

kernel/irq/manage.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -757,6 +757,16 @@ __setup_irq(unsigned int irq, struct irq_desc desc, struct irqaction new)
		if (new->flags & IRQF_ONESHOT)
		desc->status \|= IRQ_ONESHOT;

		/*
		* Force MSI interrupts to run with interrupts
		* disabled. The multi vector cards can cause stack
		* overflows due to nested interrupts when enough of
		* them are directed to a core and fire at the same
		* time.
		*/
		if (desc->msi_desc)
		new->flags \|= IRQF_DISABLED;

		if (!(desc->status & IRQ_NOAUTOEN)) {
		desc->depth = 0;
		desc->status &= ~IRQ_DISABLED;

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