MIPS: Loongson: Fix COP2 usage for preemptible kernel

In preemptible kernel, only TIF_USEDFPU flag is reliable to distinguish
whether _init_fpu()/_restore_fp() is needed. Because the value of the
CP0_Status.CU1 isn't changed during preemption.

V2: Fix coding style.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/7515/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/loongson/loongson-3/cop2-ex.c b/arch/mips/loongson/loongson-3/cop2-ex.c
index 9182e8d..b03e37d 100644 (file)
--- a/arch/mips/loongson/loongson-3/cop2-ex.c
+++ b/arch/mips/loongson/loongson-3/cop2-ex.c
@@ -22,13 +22,13 @@
 static int loongson_cu2_call(struct notifier_block *nfb, unsigned long action,
        void *data)
 {
-       int fpu_enabled;
+       int fpu_owned;
        int fr = !test_thread_flag(TIF_32BIT_FPREGS);
 
        switch (action) {
        case CU2_EXCEPTION:
                preempt_disable();
-               fpu_enabled = read_c0_status() & ST0_CU1;
+               fpu_owned = __is_fpu_owner();
                if (!fr)
                        set_c0_status(ST0_CU1 | ST0_CU2);
                else
@@ -39,8 +39,8 @@ static int loongson_cu2_call(struct notifier_block *nfb, unsigned long action,
                        KSTK_STATUS(current) |= ST0_FR;
                else
                        KSTK_STATUS(current) &= ~ST0_FR;
-               /* If FPU is enabled, we needn't init or restore fp */
-               if(!fpu_enabled) {
+               /* If FPU is owned, we needn't init or restore fp */
+               if (!fpu_owned) {
                        set_thread_flag(TIF_USEDFPU);
                        if (!used_math()) {
                                _init_fpu();