arm64: let the core code deal with preempt_count (64681787) · Commits · 戴 / test

Commit (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>

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

Admin message