linux-kernel - [PATCH 2/2] arm64: Mark the recheduling IPI as naked interrupt

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Date:   Sun,  1 Nov 2020 13:14:30 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     LAK <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <Valentin.Schneider@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: [PATCH 2/2] arm64: Mark the recheduling IPI as naked interrupt

Flag the rescheduling IPI as 'naked', making sure such interrupt
doesn't trigger a rescheduling event by itself.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kernel/smp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 82e75fc2c903..6c11be3e74d3 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -993,6 +993,10 @@ void __init set_smp_ipi_range(int ipi_base, int n)
 
 		ipi_desc[i] = irq_to_desc(ipi_base + i);
 		irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
+
+		/* The recheduling IPI is special... */
+		if (i == IPI_RESCHEDULE)
+			irq_set_status_flags(ipi_base + i, IRQ_NAKED);
 	}
 
 	ipi_irq_base = ipi_base;
-- 
2.28.0