Currently portions of our preempt logic are written in C while other
parts are written in assembly. There's no reason any of this needs to
live in assembly, so let's move the rest of the lgoic to C. At the same
time, let's make the comment a bit clearer.

Other than the increased lockdep coverage there should be no functional
change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/entry-common.c | 12 ++++++++++++
 arch/arm64/kernel/entry.S        | 13 -------------
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 1fe60578e556..dbe0bb09fe86 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c

@@ -121,6 +121,18 @@ asmlinkage void __sched arm64_preempt_schedule_irq(void)
 {
 	lockdep_assert_irqs_disabled();
 
+	if (preempt_count() != 0)
+		return;

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 656f3129bfef..8c7ddd651756 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S

@@ -561,20 +561,7 @@ tsk	.req	x28		// current thread_info
 	irq_handler	\handler
 
 #ifdef CONFIG_PREEMPTION
-	ldr	x24, [tsk, #TSK_TI_PREEMPT]	// get preempt count