[Crash-utility] Problem with "timer" command on RHEL7.6

[Kazuhito Hagio]

Hi Dave,

I noticed that the "timer" command prints somewhat wrongly for RHEL7.6 or
later kernels (not including RHEL8 / upstream) and found that it is because
struct tvec and tvec_root have an array of list_head, instead of hlist_head
in upstream kernels.

So the following patch looks good only for RHEL7, but I don't know how we
should determine the list type in order to switch the size, etc in this case.
What do you think?

Thanks,
Kazu

---
diff --git a/kernel.c b/kernel.c
index a79e5a3010ea..419cca3ac7ae 100644
--- a/kernel.c
+++ b/kernel.c
@@ -8376,7 +8376,7 @@ dump_timer_data_tvec_bases_v3(const ulong *cpus)
 	char buf4[BUFSIZE];
 
 	vec_root_size = vec_size = 0;
-	head_size = SIZE(hlist_head);
+	head_size = SIZE(list_head);
 
 	if ((i = get_array_length("tvec_root.vec", NULL, head_size)))
 		vec_root_size = i;
@@ -8804,19 +8804,19 @@ do_timer_list_v3(ulong vec_kvaddr,
 			tdx++;
 	}
 
-	readmem(vec_kvaddr, KVADDR, vec, SIZE(hlist_head) * size, 
+	readmem(vec_kvaddr, KVADDR, vec, SIZE(list_head) * size,
 		"timer_list vec array", FAULT_ON_ERROR);
 
 	ld = &list_data;
 	timer_list_buf = GETBUF(SIZE(timer_list));
 
-	for (i = count = 0; i < size; i++, vec_kvaddr += SIZE(hlist_head)) {
+	for (i = count = 0; i < size; i++, vec_kvaddr += SIZE(list_head)) {
 
-		if (vec[i] == 0)
+		if (vec[i*2] == vec_kvaddr)
 			continue;
 
 		BZERO(ld, sizeof(struct list_data));
-		ld->start = vec[i];
+		ld->start = vec[i*2];
 		ld->list_head_offset = OFFSET(timer_list_entry);
 		ld->end = vec_kvaddr;
 		ld->flags = RETURN_ON_LIST_ERROR;