MIPS: Loongson-3: Fix a cpu-hotplug issue in loongson3_ipi_interrupt()

setup_per_cpu_areas() only setup __per_cpu_offset[] for each possible
cpu, but loongson_sysconf.nr_cpus can be greater than possible cpus
(due to reserved_cpus_mask). So in loongson3_ipi_interrupt(), percpu
access will touch the original varible in .data..percpu section which
has been freed. Without this patch, cpu-hotplug will cause memery
corruption.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/10524/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/loongson/loongson-3/smp.c b/arch/mips/loongson/loongson-3/smp.c
index e3c68b5..509877c 100644 (file)
--- a/arch/mips/loongson/loongson-3/smp.c
+++ b/arch/mips/loongson/loongson-3/smp.c
@@ -272,7 +272,7 @@ void loongson3_ipi_interrupt(struct pt_regs *regs)
        if (action & SMP_ASK_C0COUNT) {
                BUG_ON(cpu != 0);
                c0count = read_c0_count();
-               for (i = 1; i < loongson_sysconf.nr_cpus; i++)
+               for (i = 1; i < num_possible_cpus(); i++)
                        per_cpu(core0_c0count, i) = c0count;
        }
 }