4 files changed, 31 insertions, 24 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 105d5609ff57..913f90692a36 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -201,13 +201,13 @@ int dump_spe(struct pt_regs *regs, elf_vrregset_t *evrregs)
 }
 #endif /* CONFIG_SPE */
 
+#ifndef CONFIG_SMP
 /*
  * If we are doing lazy switching of CPU state (FP, altivec or SPE),
  * and the current task has some state, discard it.
  */
-static inline void discard_lazy_cpu_state(void)
+void discard_lazy_cpu_state(void)
 {
-#ifndef CONFIG_SMP
         preempt_disable();
         if (last_task_used_math == current)
                 last_task_used_math = NULL;
@@ -220,8 +220,8 @@ static inline void discard_lazy_cpu_state(void)
                 last_task_used_spe = NULL;
 #endif
         preempt_enable();
-#endif /* CONFIG_SMP */
 }
+#endif /* CONFIG_SMP */
 
 int set_dabr(unsigned long dabr)
 {
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index d3f0b6d452fb..177bba78fb0b 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -497,6 +497,15 @@ static long restore_user_regs(struct pt_regs *regs,
         if (err)
                 return 1;
 
+        /*
+         * Do this before updating the thread state in
+         * current->thread.fpr/vr/evr.  That way, if we get preempted
+         * and another task grabs the FPU/Altivec/SPE, it won't be
+         * tempted to save the current CPU state into the thread_struct
+         * and corrupt what we are writing there.
+         */
+        discard_lazy_cpu_state();
+
         /* force the process to reload the FP registers from
            current->thread when it next does FP instructions */
         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1);
@@ -538,18 +547,6 @@ static long restore_user_regs(struct pt_regs *regs,
                 return 1;
 #endif /* CONFIG_SPE */
 
-#ifndef CONFIG_SMP
-        preempt_disable();
-        if (last_task_used_math == current)
-                last_task_used_math = NULL;
-        if (last_task_used_altivec == current)
-                last_task_used_altivec = NULL;
-#ifdef CONFIG_SPE
-        if (last_task_used_spe == current)
-                last_task_used_spe = NULL;
-#endif
-        preempt_enable();
-#endif
         return 0;
 }
 
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 5462bef898f6..7b9d999e2115 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -207,10 +207,20 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 
         if (!sig)
                 regs->gpr[13] = save_r13;
-        err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
         if (set != NULL)
                 err |=  __get_user(set->sig[0], &sc->oldmask);
 
+        /*
+         * Do this before updating the thread state in
+         * current->thread.fpr/vr.  That way, if we get preempted
+         * and another task grabs the FPU/Altivec, it won't be
+         * tempted to save the current CPU state into the thread_struct
+         * and corrupt what we are writing there.
+         */
+        discard_lazy_cpu_state();
+
+        err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
+
 #ifdef CONFIG_ALTIVEC
         err |= __get_user(v_regs, &sc->v_regs);
         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
@@ -229,14 +239,6 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
                 current->thread.vrsave = 0;
 #endif /* CONFIG_ALTIVEC */
 
-#ifndef CONFIG_SMP
-        preempt_disable();
-        if (last_task_used_math == current)
-                last_task_used_math = NULL;
-        if (last_task_used_altivec == current)
-                last_task_used_altivec = NULL;
-        preempt_enable();
-#endif
         /* Force reload of FP/VEC */
         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
 
diff --git a/include/asm-powerpc/system.h b/include/asm-powerpc/system.h
index 0c58e32a9570..4c888303e85b 100644
--- a/include/asm-powerpc/system.h
+++ b/include/asm-powerpc/system.h
@@ -133,6 +133,14 @@ extern int fix_alignment(struct pt_regs *);
 extern void cvt_fd(float *from, double *to, struct thread_struct *thread);
 extern void cvt_df(double *from, float *to, struct thread_struct *thread);
 
+#ifndef CONFIG_SMP
+extern void discard_lazy_cpu_state(void);
+#else
+static inline void discard_lazy_cpu_state(void)
+{
+}
+#endif
+
 #ifdef CONFIG_ALTIVEC
 extern void flush_altivec_to_thread(struct task_struct *);
 #else