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arm64: let the core code deal with preempt_count

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Commit f27dde8dee (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: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Marc Zyngier 2013-11-12 17:11:53 +00:00 • committed by Catalin Marinas
commit 6468178767
1 changed files with 7 additions and 22 deletions
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29
arch/arm64/kernel/entry.S
View file

@ -309,15 +309,12 @@ el1_irq:
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
irq_handler
#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
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