kmemleak: Do not trigger a scan when reading the debug/kmemleak file
Since there is a kernel thread for automatically scanning the memory, it
makes sense for the debug/kmemleak file to only show its findings. This
patch also adds support for "echo scan > debug/kmemleak" to trigger an
intermediate memory scan and eliminates the kmemleak_mutex (scan_mutex
covers all the cases now).
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 4130a48..e96e0ec 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -48,10 +48,10 @@
* scanned. This list is only modified during a scanning episode when the
* scan_mutex is held. At the end of a scan, the gray_list is always empty.
* Note that the kmemleak_object.use_count is incremented when an object is
- * added to the gray_list and therefore cannot be freed
- * - kmemleak_mutex (mutex): prevents multiple users of the "kmemleak" debugfs
- * file together with modifications to the memory scanning parameters
- * including the scan_thread pointer
+ * added to the gray_list and therefore cannot be freed. This mutex also
+ * prevents multiple users of the "kmemleak" debugfs file together with
+ * modifications to the memory scanning parameters including the scan_thread
+ * pointer
*
* The kmemleak_object structures have a use_count incremented or decremented
* using the get_object()/put_object() functions. When the use_count becomes
@@ -195,10 +195,8 @@
static signed long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
static int kmemleak_stack_scan = 1;
-/* mutex protecting the memory scanning */
+/* protects the memory scanning, parameters and debug/kmemleak file access */
static DEFINE_MUTEX(scan_mutex);
-/* mutex protecting the access to the /sys/kernel/debug/kmemleak file */
-static DEFINE_MUTEX(kmemleak_mutex);
/* number of leaks reported (for limitation purposes) */
static int reported_leaks;
@@ -927,6 +925,7 @@
struct kmemleak_object *object, *tmp;
struct task_struct *task;
int i;
+ int new_leaks = 0;
/* prepare the kmemleak_object's */
rcu_read_lock();
@@ -1024,6 +1023,26 @@
object = tmp;
}
WARN_ON(!list_empty(&gray_list));
+
+ /*
+ * Scanning result reporting.
+ */
+ rcu_read_lock();
+ list_for_each_entry_rcu(object, &object_list, object_list) {
+ spin_lock_irqsave(&object->lock, flags);
+ if (unreferenced_object(object) &&
+ !(object->flags & OBJECT_REPORTED)) {
+ object->flags |= OBJECT_REPORTED;
+ new_leaks++;
+ }
+ spin_unlock_irqrestore(&object->lock, flags);
+ }
+ rcu_read_unlock();
+
+ if (new_leaks)
+ pr_info("%d new suspected memory leaks (see "
+ "/sys/kernel/debug/kmemleak)\n", new_leaks);
+
}
/*
@@ -1045,33 +1064,12 @@
}
while (!kthread_should_stop()) {
- struct kmemleak_object *object;
signed long timeout = jiffies_scan_wait;
- int new_leaks = 0;
mutex_lock(&scan_mutex);
-
kmemleak_scan();
-
- rcu_read_lock();
- list_for_each_entry_rcu(object, &object_list, object_list) {
- unsigned long flags;
-
- spin_lock_irqsave(&object->lock, flags);
- if (unreferenced_object(object) &&
- !(object->flags & OBJECT_REPORTED)) {
- object->flags |= OBJECT_REPORTED;
- new_leaks++;
- }
- spin_unlock_irqrestore(&object->lock, flags);
- }
- rcu_read_unlock();
-
- if (new_leaks)
- pr_info("%d new suspected memory leaks (see "
- "/sys/kernel/debug/kmemleak)\n", new_leaks);
-
mutex_unlock(&scan_mutex);
+
/* wait before the next scan */
while (timeout && !kthread_should_stop())
timeout = schedule_timeout_interruptible(timeout);
@@ -1084,7 +1082,7 @@
/*
* Start the automatic memory scanning thread. This function must be called
- * with the kmemleak_mutex held.
+ * with the scan_mutex held.
*/
void start_scan_thread(void)
{
@@ -1099,7 +1097,7 @@
/*
* Stop the automatic memory scanning thread. This function must be called
- * with the kmemleak_mutex held.
+ * with the scan_mutex held.
*/
void stop_scan_thread(void)
{
@@ -1119,10 +1117,8 @@
struct kmemleak_object *object;
loff_t n = *pos;
- if (!n) {
- kmemleak_scan();
+ if (!n)
reported_leaks = 0;
- }
if (reported_leaks >= REPORTS_NR)
return NULL;
@@ -1206,13 +1202,10 @@
if (!atomic_read(&kmemleak_enabled))
return -EBUSY;
- ret = mutex_lock_interruptible(&kmemleak_mutex);
+ ret = mutex_lock_interruptible(&scan_mutex);
if (ret < 0)
goto out;
if (file->f_mode & FMODE_READ) {
- ret = mutex_lock_interruptible(&scan_mutex);
- if (ret < 0)
- goto kmemleak_unlock;
ret = seq_open(file, &kmemleak_seq_ops);
if (ret < 0)
goto scan_unlock;
@@ -1221,8 +1214,6 @@
scan_unlock:
mutex_unlock(&scan_mutex);
-kmemleak_unlock:
- mutex_unlock(&kmemleak_mutex);
out:
return ret;
}
@@ -1231,11 +1222,9 @@
{
int ret = 0;
- if (file->f_mode & FMODE_READ) {
+ if (file->f_mode & FMODE_READ)
seq_release(inode, file);
- mutex_unlock(&scan_mutex);
- }
- mutex_unlock(&kmemleak_mutex);
+ mutex_unlock(&scan_mutex);
return ret;
}
@@ -1250,6 +1239,7 @@
* scan=off - stop the automatic memory scanning thread
* scan=... - set the automatic memory scanning period in seconds (0 to
* disable it)
+ * scan - trigger a memory scan
*/
static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
size_t size, loff_t *ppos)
@@ -1287,7 +1277,9 @@
jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
start_scan_thread();
}
- } else
+ } else if (strncmp(buf, "scan", 4) == 0)
+ kmemleak_scan();
+ else
return -EINVAL;
/* ignore the rest of the buffer, only one command at a time */
@@ -1312,11 +1304,9 @@
{
struct kmemleak_object *object;
- mutex_lock(&kmemleak_mutex);
- stop_scan_thread();
- mutex_unlock(&kmemleak_mutex);
-
mutex_lock(&scan_mutex);
+ stop_scan_thread();
+
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list)
delete_object(object->pointer);
@@ -1458,9 +1448,9 @@
&kmemleak_fops);
if (!dentry)
pr_warning("Failed to create the debugfs kmemleak file\n");
- mutex_lock(&kmemleak_mutex);
+ mutex_lock(&scan_mutex);
start_scan_thread();
- mutex_unlock(&kmemleak_mutex);
+ mutex_unlock(&scan_mutex);
pr_info("Kernel memory leak detector initialized\n");