Currently if you disable kmemleak without stopping kmemleak scan
thread, the kmemleak objects can never be freed. It's about 370MB
on my system.
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
1200264 1197433 99% 0.30K 46164 26 369312K kmemleak_object
With this patch, it's allowed to free those objects by extending the
"clear" command.
# echo off > kmemleak
# echo clear > kmemleak
Also inform users if kmemleak is disabled but internal objects are
not freed.
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
---
Documentation/kmemleak.txt | 20 +++++++++++++++++++-
mm/kmemleak.c | 44 +++++++++++++++++++++++++++++++-------------
2 files changed, 50 insertions(+), 14 deletions(-)
diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt
index 6dc8013..f2b21bb 100644
--- a/Documentation/kmemleak.txt
+++ b/Documentation/kmemleak.txt
@@ -51,7 +51,8 @@ Memory scanning parameters can be modified at run-time by writing to the
(default 600, 0 to stop the automatic scanning)
scan - trigger a memory scan
clear - clear list of current memory leak suspects, done by
- marking all current reported unreferenced objects grey
+ marking all current reported unreferenced objects grey.
+ Or free all kmemleak objects if kmemleak has been disabled.
dump=<addr> - dump information about the object found at <addr>
Kmemleak can also be disabled at boot-time by passing "kmemleak=off" on
@@ -118,6 +119,23 @@ Then as usual to get your report with:
# cat /sys/kernel/debug/kmemleak
+Freeing kmemleak internal objects
+---------------------------------
+
+To allow access to previosuly found memory leaks even when an error fatal
+to kmemleak happens, internal kmemleak objects won't be freed when kmemleak
+is disabled, and those objects may occupy a large part of physical
+memory.
+
+If you want to make sure they're freed before disabling kmemleak:
+
+ # echo scan=off > /sys/kernel/debug/kmemleak
+ # echo off > /sys/kernel/debug/kmemleak
+
+If kmemleak has been disabled, you can reclaim memory with:
+
+ # echo clear > /sys/kernel/debug/kmemleak
+
Kmemleak API
------------
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 31f01c5..c7d4b94 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1594,6 +1594,8 @@ static void kmemleak_clear(void)
rcu_read_unlock();
}
+static void __kmemleak_do_cleanup(void);
+
/*
* File write operation to configure kmemleak at run-time. The following
* commands can be written to the /sys/kernel/debug/kmemleak file:
@@ -1606,7 +1608,8 @@ static void kmemleak_clear(void)
* disable it)
* scan - trigger a memory scan
* clear - mark all current reported unreferenced kmemleak objects as
- * grey to ignore printing them
+ * grey to ignore printing them, or free all kmemleak objects
+ * if kmemleak has been disabled.
* dump=... - dump information about the object found at the given address
*/
static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
@@ -1616,9 +1619,6 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
int buf_size;
int ret;
- if (!atomic_read(&kmemleak_enabled))
- return -EBUSY;
-
buf_size = min(size, (sizeof(buf) - 1));
if (strncpy_from_user(buf, user_buf, buf_size) < 0)
return -EFAULT;
@@ -1628,6 +1628,19 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
if (ret < 0)
return ret;
+ if (strncmp(buf, "clear", 5) == 0) {
+ if (atomic_read(&kmemleak_enabled))
+ kmemleak_clear();
+ else
+ __kmemleak_do_cleanup();
+ goto out;
+ }
+
+ if (!atomic_read(&kmemleak_enabled)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
if (strncmp(buf, "off", 3) == 0)
kmemleak_disable();
else if (strncmp(buf, "stack=on", 8) == 0)
@@ -1651,8 +1664,6 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
}
} else if (strncmp(buf, "scan", 4) == 0)
kmemleak_scan();
- else if (strncmp(buf, "clear", 5) == 0)
- kmemleak_clear();
else if (strncmp(buf, "dump=", 5) == 0)
ret = dump_str_object_info(buf + 5);
else
@@ -1677,6 +1688,16 @@ static const struct file_operations kmemleak_fops = {
.release = kmemleak_release,
};
+static void __kmemleak_do_cleanup(void)
+{
+ struct kmemleak_object *object;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(object, &object_list, object_list)
+ delete_object_full(object->pointer);
+ rcu_read_unlock();
+}
+
/*
* Stop the memory scanning thread and free the kmemleak internal objects if
* no previous scan thread (otherwise, kmemleak may still have some useful
@@ -1684,18 +1705,15 @@ static const struct file_operations kmemleak_fops = {
*/
static void kmemleak_do_cleanup(struct work_struct *work)
{
- struct kmemleak_object *object;
bool cleanup = scan_thread == NULL;
mutex_lock(&scan_mutex);
stop_scan_thread();
- if (cleanup) {
- rcu_read_lock();
- list_for_each_entry_rcu(object, &object_list, object_list)
- delete_object_full(object->pointer);
- rcu_read_unlock();
- }
+ if (cleanup)
+ __kmemleak_do_cleanup();
+ else
+ pr_info("You may free internal objects by \"echo clear > kmemleak\"\n");
mutex_unlock(&scan_mutex);
}
--
1.8.0.2
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