Subject: [PATCH] Don't panic when EEH_MAX_FAILS is exceeded

From: Mike Mason <[email-masked]>
Date: Sun, 20 Jul 2008 11:28:36 -0700

This patch changes the EEH_MAX_FAILS action from panic to printing an error message.  Panicking under under this condition is too harsh.  Although performance will be affected and the device may not recover, the system is still running, which at the very least, should allow for a more graceful shutdown.  The panic() is now wrapped in a DEBUG statement for development purposes.  The patch also removes the msleep() within a spinlock, which is not allowed.

Signed-off-by: Mike Mason <[email-masked]> 

--- powerpc.git/arch/powerpc/platforms/pseries/eeh.c	2008-07-18 08:51:42.000000000 -0700
+++ powerpc.git-new/arch/powerpc/platforms/pseries/eeh.c	2008-07-18 13:26:37.000000000 -0700
@@ -75,9 +75,9 @@
  */
 
 /* If a device driver keeps reading an MMIO register in an interrupt
- * handler after a slot isolation event has occurred, we assume it
- * is broken and panic.  This sets the threshold for how many read
- * attempts we allow before panicking.
+ * handler after a slot isolation event, it might be broken.
+ * This sets the threshold for how many read attempts we allow
+ * before printing an error message.
  */
 #define EEH_MAX_FAILS	2100000
 
@@ -470,6 +470,7 @@
 	unsigned long flags;
 	struct pci_dn *pdn;
 	int rc = 0;
+	const char *location;
 
 	total_mmio_ffs++;
 
@@ -509,18 +510,24 @@
 	rc = 1;
 	if (pdn->eeh_mode & EEH_MODE_ISOLATED) {
 		pdn->eeh_check_count ++;
-		if (pdn->eeh_check_count >= EEH_MAX_FAILS) {
-			printk (KERN_ERR "EEH: Device driver ignored %d bad reads, panicing\n",
-			        pdn->eeh_check_count);
+		if (pdn->eeh_check_count % EEH_MAX_FAILS == 0) {
+			location = (char *) of_get_property(dn, "ibm,loc-code", NULL);
+			printk (KERN_ERR "EEH: %d reads ignored for recovering device at "
+				"location=%s driver=%s pci addr=%s\n",
+				pdn->eeh_check_count, location,
+				dev->driver->name, pci_name(dev));
+			printk (KERN_ERR "EEH: Might be infinite loop in %s driver\n",
+				dev->driver->name);
+#ifdef DEBUG
 			dump_stack();
-			msleep(5000);
-			
+
 			/* re-read the slot reset state */
 			if (read_slot_reset_state(pdn, rets) != 0)
 				rets[0] = -1;	/* reset state unknown */
 
 			/* If we are here, then we hit an infinite loop. Stop. */
 			panic("EEH: MMIO halt (%d) on device:%s\n", rets[0], pci_name(dev));
+#endif
 		}
 		goto dn_unlock;
 	}