sparc64: Make prom entry spinlock NMI safe.

[ Upstream commit 8a4fd1e4 ]

If we do something like try to print to the OF console from an NMI
while we're already in OpenFirmware, we'll deadlock on the spinlock.

Use a raw spinlock and disable NMIs when we take it.
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/sparc/prom/p1275.c

@@ -32,8 +32,7 @@ extern void prom_cif_interface(void);
 extern void prom_cif_callback(void);
 
 /*
- * This provides SMP safety on the p1275buf. prom_callback() drops this lock
- * to allow recursuve acquisition.
+ * This provides SMP safety on the p1275buf.
  */
 DEFINE_SPINLOCK(prom_entry_lock);
 
@@ -47,7 +46,9 @@ long p1275_cmd(const char *service, long fmt, ...)
 	
 	p = p1275buf.prom_buffer;
 
-	spin_lock_irqsave(&prom_entry_lock, flags);
+	raw_local_save_flags(flags);
+	raw_local_irq_restore(PIL_NMI);
+	spin_lock(&prom_entry_lock);
 
 	p1275buf.prom_args[0] = (unsigned long)p;		/* service */
 	strcpy (p, service);
@@ -139,7 +140,8 @@ long p1275_cmd(const char *service, long fmt, ...)
 	va_end(list);
 	x = p1275buf.prom_args [nargs + 3];
 
-	spin_unlock_irqrestore(&prom_entry_lock, flags);
+	spin_unlock(&prom_entry_lock);
+	raw_local_irq_restore(flags);
 
 	return x;
 }