[PATCH v3 05/20] arm64: entry: move preempt logic to C
From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-05-25 18:36:22
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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; + + /* + * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC + * priority masking is used the GIC irqchip driver will clear DAIF.IF + * using gic_arch_enable_irqs() for normal IRQs. If anything is set in + * DAIF we must have handled an NMI, so skip preemption. + */ + if (system_uses_irq_prio_masking() && read_sysreg(daif)) + return; + /* * Preempting a task from an IRQ means we leave copies of PSTATE * on the stack. cpufeature's enable calls may modify PSTATE, but
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 -alternative_if ARM64_HAS_IRQ_PRIO_MASKING - /* - * DA were cleared at start of handling, and IF are cleared by - * the GIC irqchip driver using gic_arch_enable_irqs() for - * normal IRQs. If anything is set, it means we come back from - * an NMI instead of a normal IRQ, so skip preemption - */ - mrs x0, daif - orr x24, x24, x0 -alternative_else_nop_endif - cbnz x24, 1f // preempt count != 0 || NMI return path bl arm64_preempt_schedule_irq // irq en/disable is done inside -1: #endif mov x0, sp
--
2.11.0
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