The build breaks when STACKTRACE=n, eg. skiroot_defconfig:
  arch/powerpc/kernel/eeh_event.c:124:23: error: implicit declaration of function 'stack_trace_save'
Fix it with some ifdefs for now.
Fixes: 25baf3d81614 ("powerpc/eeh: Defer printing stack trace")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
        struct list_head child;         /* Memb. child_list/eeh_phb_pe  */
        struct list_head edevs;         /* List of eeh_dev in this PE   */
 
+#ifdef CONFIG_STACKTRACE
        /*
         * Saved stack trace. When we find a PE freeze in eeh_dev_check_failure
         * the stack trace is saved here so we can print it in the recovery
         */
        unsigned long stack_trace[64];
        int trace_entries;
+#endif /* CONFIG_STACKTRACE */
 };
 
 #define eeh_pe_for_each_dev(pe, edev, tmp) \
 
                       eeh_pe_loc_get(pe), eeh_pe_loc_get(phb_pe));
        }
 
+#ifdef CONFIG_STACKTRACE
        /*
         * Print the saved stack trace now that we've verified there's
         * something to recover.
 
                pe->trace_entries = 0;
        }
-
+#endif /* CONFIG_STACKTRACE */
 
        eeh_pe_update_time_stamp(pe);
        pe->freeze_count++;
 
         * while the PE is sitting in the event queue.
         */
        if (pe) {
+#ifdef CONFIG_STACKTRACE
                /*
                 * Save the current stack trace so we can dump it from the
                 * event handler thread.
                 */
                pe->trace_entries = stack_trace_save(pe->stack_trace,
                                         ARRAY_SIZE(pe->stack_trace), 0);
+#endif /* CONFIG_STACKTRACE */
 
                eeh_pe_state_mark(pe, EEH_PE_RECOVERING);
        }