percpu: make allocation failures more verbose

Warn and dump stack when percpu allocation fails. percpu allocator is still young and unchecked NULL percpu pointer usage can result in random memory corruption when combined with the pointer shifting in access macros. Allocation failures should be rare and the warning message will be disabled after certain times. Signed-off-by: Tejun Heo <tj@kernel.org>

percpu: make allocation failures more verbose
Warn and dump stack when percpu allocation fails. percpu allocator is still young and unchecked NULL percpu pointer usage can result in random memory corruption when combined with the pointer shifting in access macros. Allocation failures should be rare and the warning message will be disabled after certain times. Signed-off-by: Tejun Heo <tj@kernel.org>
Tejun Heo
1 parent 635b75fc18
Showing 1 changed file with 18 additions and 2 deletions Side-by-side Diff
mm/percpu.c
@@ -1043,7 +1043,9 @@
  */
 static void *pcpu_alloc(size_t size, size_t align, bool reserved)
 {
+	static int warn_limit = 10;
 	struct pcpu_chunk *chunk;
+	const char *err;
 	int slot, off;
  
 	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {
  
  
@@ -1059,11 +1061,14 @@
 	if (reserved && pcpu_reserved_chunk) {
 		chunk = pcpu_reserved_chunk;
 		if (size > chunk->contig_hint ||
-		    pcpu_extend_area_map(chunk) < 0)
+		    pcpu_extend_area_map(chunk) < 0) {
+			err = "failed to extend area map of reserved chunk";
 			goto fail_unlock;
+		}
 		off = pcpu_alloc_area(chunk, size, align);
 		if (off >= 0)
 			goto area_found;
+		err = "alloc from reserved chunk failed";
 		goto fail_unlock;
 	}
  
@@ -1080,6 +1085,7 @@
 			case 1:
 				goto restart;	/* pcpu_lock dropped, restart */
 			default:
+				err = "failed to extend area map";
 				goto fail_unlock;
 			}
  
  
@@ -1093,8 +1099,10 @@
 	spin_unlock_irq(&pcpu_lock);
  
 	chunk = alloc_pcpu_chunk();
-	if (!chunk)
+	if (!chunk) {
+		err = "failed to allocate new chunk";
 		goto fail_unlock_mutex;
+	}
  
 	spin_lock_irq(&pcpu_lock);
 	pcpu_chunk_relocate(chunk, -1);
@@ -1107,6 +1115,7 @@
 	if (pcpu_populate_chunk(chunk, off, size)) {
 		spin_lock_irq(&pcpu_lock);
 		pcpu_free_area(chunk, off);
+		err = "failed to populate";
 		goto fail_unlock;
 	}
  
@@ -1119,6 +1128,13 @@
 	spin_unlock_irq(&pcpu_lock);
 fail_unlock_mutex:
 	mutex_unlock(&pcpu_alloc_mutex);
+	if (warn_limit) {
+		pr_warning("PERCPU: allocation failed, size=%zu align=%zu, "
+			   "%s\n", size, align, err);
+		dump_stack();
+		if (!--warn_limit)
+			pr_info("PERCPU: limit reached, disable warning\n");
+	}
 	return NULL;
 }
...	...	@@ -1043,7 +1043,9 @@
1043	1043	*/
1044	1044	static void *pcpu_alloc(size_t size, size_t align, bool reserved)
1045	1045	{
	1046	+ static int warn_limit = 10;
1046	1047	struct pcpu_chunk *chunk;
	1048	+ const char *err;
1047	1049	int slot, off;
1048	1050
1049	1051	if (unlikely(!size \|\| size > PCPU_MIN_UNIT_SIZE \|\| align > PAGE_SIZE)) {
1050	1052
1051	1053
...	...	@@ -1059,11 +1061,14 @@
1059	1061	if (reserved && pcpu_reserved_chunk) {
1060	1062	chunk = pcpu_reserved_chunk;
1061	1063	if (size > chunk->contig_hint \|\|
1062		- pcpu_extend_area_map(chunk) < 0)
	1064	+ pcpu_extend_area_map(chunk) < 0) {
	1065	+ err = "failed to extend area map of reserved chunk";
1063	1066	goto fail_unlock;
	1067	+ }
1064	1068	off = pcpu_alloc_area(chunk, size, align);
1065	1069	if (off >= 0)
1066	1070	goto area_found;
	1071	+ err = "alloc from reserved chunk failed";
1067	1072	goto fail_unlock;
1068	1073	}
1069	1074
...	...	@@ -1080,6 +1085,7 @@
1080	1085	case 1:
1081	1086	goto restart; /* pcpu_lock dropped, restart */
1082	1087	default:
	1088	+ err = "failed to extend area map";
1083	1089	goto fail_unlock;
1084	1090	}
1085	1091
1086	1092
...	...	@@ -1093,8 +1099,10 @@
1093	1099	spin_unlock_irq(&pcpu_lock);
1094	1100
1095	1101	chunk = alloc_pcpu_chunk();
1096		- if (!chunk)
	1102	+ if (!chunk) {
	1103	+ err = "failed to allocate new chunk";
1097	1104	goto fail_unlock_mutex;
	1105	+ }
1098	1106
1099	1107	spin_lock_irq(&pcpu_lock);
1100	1108	pcpu_chunk_relocate(chunk, -1);
...	...	@@ -1107,6 +1115,7 @@
1107	1115	if (pcpu_populate_chunk(chunk, off, size)) {
1108	1116	spin_lock_irq(&pcpu_lock);
1109	1117	pcpu_free_area(chunk, off);
	1118	+ err = "failed to populate";
1110	1119	goto fail_unlock;
1111	1120	}
1112	1121
...	...	@@ -1119,6 +1128,13 @@
1119	1128	spin_unlock_irq(&pcpu_lock);
1120	1129	fail_unlock_mutex:
1121	1130	mutex_unlock(&pcpu_alloc_mutex);
	1131	+ if (warn_limit) {
	1132	+ pr_warning("PERCPU: allocation failed, size=%zu align=%zu, "
	1133	+ "%s\n", size, align, err);
	1134	+ dump_stack();
	1135	+ if (!--warn_limit)
	1136	+ pr_info("PERCPU: limit reached, disable warning\n");
	1137	+ }
1122	1138	return NULL;
1123	1139	}
1124	1140