+ mm-kmemleak-rely-on-rcu-for-task-stack-scanning.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/kmemleak: rely on rcu for task stack scanning
has been added to the -mm tree.  Its filename is
     mm-kmemleak-rely-on-rcu-for-task-stack-scanning.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-kmemleak-rely-on-rcu-for-task-stack-scanning.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-kmemleak-rely-on-rcu-for-task-stack-scanning.patch

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------------------------------------------------------
From: Davidlohr Bueso <dave@stgolabs.net>
Subject: mm/kmemleak: rely on rcu for task stack scanning

kmemleak_scan() currently relies on the big tasklist_lock hammer to
stabilize iterating through the tasklist.  Instead, this patch proposes
simply using rcu along with the rcu-safe for_each_process_thread flavor
(without changing scan semantics), which doesn't make use of
next_thread/p->thread_group and thus cannot race with exit.  Furthermore,
any races with fork() and not seeing the new child should be benign as
it's not running yet and can also be detected by the next scan.

Link: https://lkml.kernel.org/r/20200820203902.11308-1-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kmemleak.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/kmemleak.c~mm-kmemleak-rely-on-rcu-for-task-stack-scanning
+++ a/mm/kmemleak.c
@@ -1471,15 +1471,15 @@ static void kmemleak_scan(void)
 	if (kmemleak_stack_scan) {
 		struct task_struct *p, *g;
 
-		read_lock(&tasklist_lock);
-		do_each_thread(g, p) {
+		rcu_read_lock();
+		for_each_process_thread(g, p) {
 			void *stack = try_get_task_stack(p);
 			if (stack) {
 				scan_block(stack, stack + THREAD_SIZE, NULL);
 				put_task_stack(p);
 			}
-		} while_each_thread(g, p);
-		read_unlock(&tasklist_lock);
+		}
+		rcu_read_unlock();
 	}
 
 	/*
_

Patches currently in -mm which might be from dave@stgolabs.net are

mm-kmemleak-rely-on-rcu-for-task-stack-scanning.patch