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Date: Thu, 13 Mar 2014 14:47:46 +0800
From: Li Zefan <lizefan@...wei.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Catalin Marinas <catalin.marinas@....com>,
LKML <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: [PATCH 1/3] kmemleak: allow freeing internal objects after disabling
kmemleak
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@...wei.com>
---
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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