sh: Fix occasional FPU register corruption under preempt.

Presently with preempt enabled there's the possibility to be preempted
after the TIF_USEDFPU test and the register save, leading to bogus
state post-__switch_to(). Use an explicit preempt_disable()/enable()
pair around unlazy_fpu()/clear_fpu() to avoid this. Follows the x86
change.

Reported-by: Takuo Koguchi <takuo.koguchi.sw@hitachi.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 18 insertions, 14 deletions

diff --git a/include/asm-sh/fpu.h b/include/asm-sh/fpu.h
index f8429880a270..f89abf5920d8 100644
--- a/include/asm-sh/fpu.h
+++ b/include/asm-sh/fpu.h
@@ -1,9 +1,8 @@
 #ifndef __ASM_SH_FPU_H
 #define __ASM_SH_FPU_H
 
-#define SR_FD    0x00008000
-
 #ifndef __ASSEMBLY__
+#include <linux/preempt.h>
 #include <asm/ptrace.h>
 
 #ifdef CONFIG_SH_FPU
@@ -28,18 +27,23 @@ extern void save_fpu(struct task_struct *__tsk, struct pt_regs *regs);
 
 extern int do_fpu_inst(unsigned short, struct pt_regs *);
 
-#define unlazy_fpu(tsk, regs) do {                      \
-        if (test_tsk_thread_flag(tsk, TIF_USEDFPU)) {   \
-                save_fpu(tsk, regs);                    \
-        }                                               \
-} while (0)
-
-#define clear_fpu(tsk, regs) do {                               \
-        if (test_tsk_thread_flag(tsk, TIF_USEDFPU)) {           \
-                clear_tsk_thread_flag(tsk, TIF_USEDFPU);        \
-                release_fpu(regs);                              \
-        }                                                       \
-} while (0)
+static inline void unlazy_fpu(struct task_struct *tsk, struct pt_regs *regs)
+{
+        preempt_disable();
+        if (test_tsk_thread_flag(tsk, TIF_USEDFPU))
+                save_fpu(tsk, regs);
+        preempt_enable();
+}
+
+static inline void clear_fpu(struct task_struct *tsk, struct pt_regs *regs)
+{
+        preempt_disable();
+        if (test_tsk_thread_flag(tsk, TIF_USEDFPU)) {
+                clear_tsk_thread_flag(tsk, TIF_USEDFPU);
+                release_fpu(regs);
+        }
+        preempt_enable();
+}
 
 #endif /* __ASSEMBLY__ */