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>

4 files changed, 20 insertions, 15 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__ */
 
diff --git a/include/asm-sh/processor.h b/include/asm-sh/processor.h
index 19fe47c1ca17..ec707b98e5b9 100644
--- a/include/asm-sh/processor.h
+++ b/include/asm-sh/processor.h
@@ -2,7 +2,6 @@
 #define __ASM_SH_PROCESSOR_H
 
 #include <asm/cpu-features.h>
-#include <asm/fpu.h>
 
 #ifndef __ASSEMBLY__
 /*
diff --git a/include/asm-sh/processor_32.h b/include/asm-sh/processor_32.h
index df2d5b039ef4..c09305d6a9d9 100644
--- a/include/asm-sh/processor_32.h
+++ b/include/asm-sh/processor_32.h
@@ -70,6 +70,7 @@ extern struct sh_cpuinfo cpu_data[];
  */
 #define SR_DSP          0x00001000
 #define SR_IMASK        0x000000f0
+#define SR_FD           0x00008000
 
 /*
  * FPU structure and data
diff --git a/include/asm-sh/processor_64.h b/include/asm-sh/processor_64.h
index eda4bef448e9..88a2edf8fa5d 100644
--- a/include/asm-sh/processor_64.h
+++ b/include/asm-sh/processor_64.h
@@ -112,6 +112,7 @@ extern struct sh_cpuinfo cpu_data[];
 #endif
 
 #define SR_IMASK 0x000000f0
+#define SR_FD    0x00008000
 #define SR_SSTEP 0x08000000
 
 #ifndef __ASSEMBLY__