linux-kernel - [PATCH] MIPS: sync-r4k: do slave counter synchronization with disabled HW interrupts

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Message-Id: <20200122123909.8188-1-s.korolev@ndmsystems.com>
Date:   Wed, 22 Jan 2020 15:39:08 +0300
From:   Sergey Korolev <s.korolev@...systems.com>
To:     linux-mips@...r.kernel.org
Cc:     s.korolev@...systems.com, Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        James Hogan <jhogan@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] MIPS: sync-r4k: do slave counter synchronization with disabled HW interrupts

synchronise_count_slave() called with an enabled in mips_clockevent_init()
timer interrupt which may decrease synchronization precision.

Signed-off-by: Sergey Korolev <s.korolev@...systems.com>
---
 arch/mips/kernel/sync-r4k.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/mips/kernel/sync-r4k.c b/arch/mips/kernel/sync-r4k.c
index f2973ce87f53..abdd7aaa3311 100644
--- a/arch/mips/kernel/sync-r4k.c
+++ b/arch/mips/kernel/sync-r4k.c
@@ -90,6 +90,9 @@ void synchronise_count_master(int cpu)
 void synchronise_count_slave(int cpu)
 {
 	int i;
+	unsigned long flags;
+
+	local_irq_save(flags);
 
 	/*
 	 * Not every cpu is online at the time this gets called,
@@ -113,5 +116,7 @@ void synchronise_count_slave(int cpu)
 	}
 	/* Arrange for an interrupt in a short while */
 	write_c0_compare(read_c0_count() + COUNTON);
+
+	local_irq_restore(flags);
 }
 #undef NR_LOOPS
-- 
2.20.1