ARM: imx: fix sync issue between imx_cpu_die and imx_cpu_kill

There is a sync issue with hotplug operation.  It's possible that when
imx_cpu_kill gets running on primary core, the imx_cpu_die execution
on the core which is to be killed hasn't been finished yet.  The problem
will very likely be hit when running suspend without no_console_suspend
setting on kernel cmdline.

It uses cpu jumping argument register to sync imx_cpu_die and
imx_cpu_kill.  The register will be set in imx_cpu_die and imx_cpu_kill
will wait for the register being cleared to actually kill the cpu.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: <stable@vger.kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/arm/mach-imx/hotplug.c b/arch/arm/mach-imx/hotplug.c
index 7bc5fe15dda..361a253e2b6 100644
--- a/arch/arm/mach-imx/hotplug.c
+++ b/arch/arm/mach-imx/hotplug.c
@@ -46,11 +46,23 @@ static inline void cpu_enter_lowpower(void)
 void imx_cpu_die(unsigned int cpu)
 {
 	cpu_enter_lowpower();
+	/*
+	 * We use the cpu jumping argument register to sync with
+	 * imx_cpu_kill() which is running on cpu0 and waiting for
+	 * the register being cleared to kill the cpu.
+	 */
+	imx_set_cpu_arg(cpu, ~0);
 	cpu_do_idle();
 }
 
 int imx_cpu_kill(unsigned int cpu)
 {
+	unsigned long timeout = jiffies + msecs_to_jiffies(50);
+
+	while (imx_get_cpu_arg(cpu) == 0)
+		if (time_after(jiffies, timeout))
+			return 0;
 	imx_enable_cpu(cpu, false);
+	imx_set_cpu_arg(cpu, 0);
 	return 1;
 }