linux-kernel - [PATCH 5.9 481/757] powerpc/64: fix irq replay missing preempt

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Message-Id: <20201027135513.042401296@linuxfoundation.org>
Date:   Tue, 27 Oct 2020 14:52:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 481/757] powerpc/64: fix irq replay missing preempt

From: Nicholas Piggin <npiggin@...il.com>

[ Upstream commit 903fd31d3212ab72d564c68f6cfb5d04db68773e ]

Prior to commit 3282a3da25bd ("powerpc/64: Implement soft interrupt
replay in C"), replayed interrupts returned by the regular interrupt
exit code, which performs preemption in case an interrupt had set
need_resched.

This logic was missed by the conversion. Adding preempt_disable/enable
around the interrupt replay and final irq enable will reschedule if
needed.

Fixes: 3282a3da25bd ("powerpc/64: Implement soft interrupt replay in C")
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20200915114650.3980244-1-npiggin@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kernel/irq.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index bf21ebd361900..77019699606a5 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -368,6 +368,12 @@ notrace void arch_local_irq_restore(unsigned long mask)
 		}
 	}
 
+	/*
+	 * Disable preempt here, so that the below preempt_enable will
+	 * perform resched if required (a replayed interrupt may set
+	 * need_resched).
+	 */
+	preempt_disable();
 	irq_soft_mask_set(IRQS_ALL_DISABLED);
 	trace_hardirqs_off();
 
@@ -377,6 +383,7 @@ notrace void arch_local_irq_restore(unsigned long mask)
 	trace_hardirqs_on();
 	irq_soft_mask_set(IRQS_ENABLED);
 	__hard_irq_enable();
+	preempt_enable();
 }
 EXPORT_SYMBOL(arch_local_irq_restore);
 
-- 
2.25.1