ipmi: hold ATTN until upper layer ready

Hold handling of ATTN until the upper layer has reported that it is
ready.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: Patrick Schoeller <Patrick.Schoeller@hp.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/ipmi/ipmi_si_intf.c

@@ -723,8 +723,11 @@ static enum si_sm_result smi_event_handler(struct smi_info *smi_info,
 		si_sm_result = smi_info->handlers->event(smi_info->si_sm, 0);
 	}
 
-	/* We prefer handling attn over new messages. */
-	if (si_sm_result == SI_SM_ATTN)
+	/*
+	 * We prefer handling attn over new messages.  But don't do
+	 * this if there is not yet an upper layer to handle anything.
+	 */
+	if (likely(smi_info->intf) && si_sm_result == SI_SM_ATTN)
 	{
 		unsigned char msg[2];