[RFC PATCH] kmemleak: Scan all thread stacks

Catalin Marinas
2009-07-17T09:38:16Z

This patch changes the for_each_process() loop with the
do_each_thread()/while_each_thread() pair. It also replaces the
read_lock(&tasklist_lock) with rcu_read_lock() and task_lock(p).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

My questions:

1. Is it correct that for_each_process() used currently by kmemleak may
not loop through all the possible kernel thread stacks?

2. Is it safe to use rcu_read_lock() and task_lock() when scanning the
corresponding kernel stack (thread_info structure)? The loop doesn't
do any modification to the task list. The reason for this is to
allow kernel preemption when scanning the stacks.

Alternatively, I can hook kmemleak callbacks into the
alloc_thread_info/free_thread_info structures but many of these are
architecture-specific.

Thanks,

Catalin

mm/kmemleak.c | 17 ++++++++++-------
1 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 983f3f6..a933128 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1064,7 +1064,6 @@ static void kmemleak_scan(void)
{
unsigned long flags;
struct kmemleak_object *object, *tmp;
- struct task_struct *task;
int i;
int new_leaks = 0;
int gray_list_pass = 0;
@@ -1135,12 +1134,16 @@ static void kmemleak_scan(void)
* not enabled by default.
*/
if (kmemleak_stack_scan) {
- read_lock(&tasklist_lock);
- for_each_process(task)
- scan_block(task_stack_page(task),
- task_stack_page(task) + THREAD_SIZE,
- NULL, 0);
- read_unlock(&tasklist_lock);
+ struct task_struct *p, *g;
+
+ rcu_read_lock();
+ do_each_thread(g, p) {
+ task_lock(p);
+ scan_block(task_stack_page(p), task_stack_page(p) +
+ THREAD_SIZE, NULL, 0);
+ task_unlock(p);
+ } while_each_thread(g, p);
+ rcu_read_unlock();
}

/*