The current implementation of ipi_cpu_stop() is just a tight infinite loop
around cpu_relax().  This infinite loop implementation is OK if the machine
will soon do a poweroff, but it doesn't have any mechanism to allow a CPU
to be brought back on-line, nor is it compatible with kexec re-boot.

Add a check for a valid cpu_die method of the appropriate cpu_ops structure,
and if a valid method is found, transfer control to that method.  It is
expected that the cpu_die method puts the CPU into a state such that they can
be brought back on-line or progress through a kexec re-boot.

Signed-off-by: Geoff Levand <[email protected]>
---
 arch/arm64/kernel/smp.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 4743397..002aa8a 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -555,6 +555,15 @@ static void ipi_cpu_stop(unsigned int cpu)
 
        local_irq_disable();
 
+       /* If we have the cpu ops use them. */
+
+       if (cpu_ops[cpu]->cpu_disable &&
+           cpu_ops[cpu]->cpu_die &&
+           !cpu_ops[cpu]->cpu_disable(cpu))
+               cpu_ops[cpu]->cpu_die(cpu);
+
+       /* Otherwise spin here. */
+
        while (1)
                cpu_relax();
 }
-- 
1.9.1



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