[PATCH] powerpc: Avoid potential FP corruption with preempt and UP

[linux-2.6-omap-h63xx.git] / arch / powerpc / kernel / signal_32.c

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index d3f0b6d452fb71d906a56fd87980f65c229c5bda..177bba78fb0b6974a7f733769ab1d489a7ecfcb1 100644 (file)
--- 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;
 }