[Crash-utility] [PATCH 1/1] CFS runqueue loop detection

[David Mair]

Here is a patch against crash v6.0.2 that adds duplicate node detection
per-CPU for the CFS runqueue display in dump_CFS_runqueues() for the
runq command.

This resolves the failure to bail-out of the unending looping display I
get with the crash dump I have that has a corrupted CFS runqueue
containing a loop.

Signed-off-by: David Mair <dmair at suse.com>
---

 task.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/task.c b/task.c
index 433a043..0333fe8 100755
--- a/task.c
+++ b/task.c
@@ -7050,7 +7050,12 @@ dump_tasks_in_cfs_rq(ulong cfs_rq, ulong skip)
 				     OFFSET(sched_entity_run_node));
 		if (!tc)
 			continue;
-		dump_task_runq_entry(tc);
+		if (hq_enter((ulong)tc)) {
+			dump_task_runq_entry(tc);
+		} else {
+			error(WARNING, "Duplicate CFS runqueue node, task %lx, probable
loop\n", tc->task);
+			return total;
+		}
 		total++;
 	}

@@ -7217,10 +7222,12 @@ dump_CFS_runqueues(void)
 		fprintf(fp, "  CFS RB_ROOT: %lx\n", (ulong)root);

 		tot = 0;
+		hq_open();
 		if (curr_cfs_rq)
 			tot += dump_tasks_in_cfs_rq(curr_cfs_rq, 0);
 		if (cfs_rq != curr_cfs_rq)
 			tot += dump_tasks_in_cfs_rq(cfs_rq, curr_cfs_rq);
+		hq_close();
 		if (!tot) {
 			INDENT(5);
 			fprintf(fp, "[no tasks queued]\n");