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Commit 64681787 authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas
Browse files

arm64: let the core code deal with preempt_count 



Commit f27dde8d (sched: Add NEED_RESCHED to the preempt_count)
introduced the use of bit 31 in preempt_count for obscure scheduling
purposes.

This causes interrupts taken from EL0 to hit the (open coded) BUG when
this flag is flipped while handling the interrupt (we compare the
values before and after, and kill the kernel if they are different).

The fix is to stop messing with the preempt count entirely, as this
is already being dealt with in the generic code (irq_enter/irq_exit).

Tested on a dual A53 FPGA running cyclictest.

Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 6ce4eac1

arch/arm64/kernel/entry.S

+7 −22
Original line number Diff line number Diff line
@@ -309,15 +309,12 @@ el1_irq: 
#ifdef CONFIG_TRACE_IRQFLAGS

	bl	trace_hardirqs_off

#endif

#ifdef CONFIG_PREEMPT

	get_thread_info tsk

	ldr	w24, [tsk, #TI_PREEMPT]		// get preempt count

	add	w0, w24, #1			// increment it

	str	w0, [tsk, #TI_PREEMPT]

#endif



	irq_handler



#ifdef CONFIG_PREEMPT

	str	w24, [tsk, #TI_PREEMPT]		// restore preempt count

	get_thread_info tsk

	ldr	w24, [tsk, #TI_PREEMPT]		// restore preempt count

	cbnz	w24, 1f				// preempt count != 0

	ldr	x0, [tsk, #TI_FLAGS]		// get flags

	tbz	x0, #TIF_NEED_RESCHED, 1f	// needs rescheduling?
@@ -507,22 +504,10 @@ el0_irq_naked: 
#ifdef CONFIG_TRACE_IRQFLAGS

	bl	trace_hardirqs_off

#endif

	get_thread_info tsk

#ifdef CONFIG_PREEMPT

	ldr	w24, [tsk, #TI_PREEMPT]		// get preempt count

	add	w23, w24, #1			// increment it

	str	w23, [tsk, #TI_PREEMPT]

#endif



	irq_handler

#ifdef CONFIG_PREEMPT

	ldr	w0, [tsk, #TI_PREEMPT]

	str	w24, [tsk, #TI_PREEMPT]

	cmp	w0, w23

	b.eq	1f

	mov	x1, #0

	str	x1, [x1]			// BUG

1:

#endif

	get_thread_info tsk



#ifdef CONFIG_TRACE_IRQFLAGS

	bl	trace_hardirqs_on

#endif