linux-kernel - [v1][PATCH 1/1] ppc64: max next_tb to prevent from replaying timer interrupt

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Date:	Wed, 16 Jan 2013 11:01:19 +0800
From:	Tiejun Chen <tiejun.chen@...driver.com>
To:	<benh@...nel.crashing.org>, <galak@...nel.crashing.org>
CC:	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>
Subject: [v1][PATCH 1/1] ppc64: max next_tb to prevent from replaying timer interrupt

With lazy interrupt, we always call __check_irq_replaysome with
decrementers_next_tb to check if we need to replay timer interrupt.
So in hotplug case we also need to set decrementers_next_tb as MAX
to make sure __check_irq_replay don't replay timer interrupt
when return as we expect, otherwise we'll trap here infinitely.

Signed-off-by: Tiejun Chen <tiejun.chen@...driver.com>
---
v1:

* In hotplug case we max decrementers_next_tb to prevent from
replaying timer interrupt for any offline CPU.

 arch/powerpc/kernel/time.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 6f6b1cc..127361e 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -494,10 +494,15 @@ void timer_interrupt(struct pt_regs * regs)
 	set_dec(DECREMENTER_MAX);
 
 	/* Some implementations of hotplug will get timer interrupts while
-	 * offline, just ignore these
+	 * offline, just ignore these and we also need to set
+	 * decrementers_next_tb as MAX to make sure __check_irq_replay
+	 * don't replay timer interrupt when return, otherwise we'll trap
+	 * here infinitely :(
 	 */
-	if (!cpu_online(smp_processor_id()))
+	if (!cpu_online(smp_processor_id())) {
+		*next_tb = ~(u64)0;
 		return;
+	}
 
 	/* Conditionally hard-enable interrupts now that the DEC has been
 	 * bumped to its maximum value
-- 
1.7.9.5

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