Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 83dbbdbb authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

android, lowmemorykiller: remove task handoff notifier 



The task handoff notifier leaks task_struct since it never gets freed
after the callback returns NOTIFY_OK, which means it is responsible for
doing so.

It turns out the lowmemorykiller actually doesn't need this notifier at
all.  It's used to prevent unnecessary killing by waiting for a thread
to exit as a result of lowmem_shrink(), however, it's possible to do
this in the same way the kernel oom killer works by setting TIF_MEMDIE
and avoid killing if we're still waiting for it to exit.

The kernel oom killer will already automatically set TIF_MEMDIE for
threads that are attempting to allocate memory that have a fatal signal.
The thread selected by lowmem_shrink() will have such a signal after the
lowmemorykiller sends it a SIGKILL, so this won't result in an
unnecessary use of memory reserves for the thread to exit.

This has the added benefit that we don't have to rely on
CONFIG_PROFILING to prevent needlessly killing tasks.

Reported-by: default avatarWerner Landgraf <w.landgraf@ru.ru>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Acked-by: default avatarColin Cross <ccross@android.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 00341028

drivers/staging/android/lowmemorykiller.c

+7 −41
Original line number Original line Diff line number Diff line
@@ -55,7 +55,6 @@ static int lowmem_minfree[6] = { 
};

};

static int lowmem_minfree_size = 4;

static int lowmem_minfree_size = 4;





static struct task_struct *lowmem_deathpending;

static unsigned long lowmem_deathpending_timeout;

static unsigned long lowmem_deathpending_timeout;





#define lowmem_print(level, x...)			\

#define lowmem_print(level, x...)			\
@@ -64,24 +63,6 @@ static unsigned long lowmem_deathpending_timeout; 
			printk(x);			\

			printk(x);			\

	} while (0)

	} while (0)





static int

task_notify_func(struct notifier_block *self, unsigned long val, void *data);



static struct notifier_block task_nb = {

	.notifier_call	= task_notify_func,

};



static int

task_notify_func(struct notifier_block *self, unsigned long val, void *data)

{

	struct task_struct *task = data;



	if (task == lowmem_deathpending)

		lowmem_deathpending = NULL;



	return NOTIFY_OK;

}



static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)

static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)

{

{

	struct task_struct *tsk;

	struct task_struct *tsk;
@@ -97,19 +78,6 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) 
	int other_file = global_page_state(NR_FILE_PAGES) -

	int other_file = global_page_state(NR_FILE_PAGES) -

						global_page_state(NR_SHMEM);

						global_page_state(NR_SHMEM);





	/*

	 * If we already have a death outstanding, then

	 * bail out right away; indicating to vmscan

	 * that we have nothing further to offer on

	 * this pass.

	 *

	 * Note: Currently you need CONFIG_PROFILING

	 * for this to work correctly.

	 */

	if (lowmem_deathpending &&

	    time_before_eq(jiffies, lowmem_deathpending_timeout))

		return 0;



	if (lowmem_adj_size < array_size)

	if (lowmem_adj_size < array_size)

		array_size = lowmem_adj_size;

		array_size = lowmem_adj_size;

	if (lowmem_minfree_size < array_size)

	if (lowmem_minfree_size < array_size)
@@ -148,6 +116,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) 
		if (!p)

		if (!p)

			continue;

			continue;





		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&

		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {

			task_unlock(p);

			rcu_read_unlock();

			return 0;

		}

		oom_score_adj = p->signal->oom_score_adj;

		oom_score_adj = p->signal->oom_score_adj;

		if (oom_score_adj < min_score_adj) {

		if (oom_score_adj < min_score_adj) {

			task_unlock(p);

			task_unlock(p);
@@ -174,15 +148,9 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) 
		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",

		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",

			     selected->pid, selected->comm,

			     selected->pid, selected->comm,

			     selected_oom_score_adj, selected_tasksize);

			     selected_oom_score_adj, selected_tasksize);

		/*

		 * If CONFIG_PROFILING is off, then we don't want to stall

		 * the killer by setting lowmem_deathpending.

		 */

#ifdef CONFIG_PROFILING

		lowmem_deathpending = selected;

		lowmem_deathpending_timeout = jiffies + HZ;

		lowmem_deathpending_timeout = jiffies + HZ;

#endif

		send_sig(SIGKILL, selected, 0);

		send_sig(SIGKILL, selected, 0);

		set_tsk_thread_flag(selected, TIF_MEMDIE);

		rem -= selected_tasksize;

		rem -= selected_tasksize;

	}

	}

	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",

	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
@@ -198,7 +166,6 @@ static struct shrinker lowmem_shrinker = { 




static int __init lowmem_init(void)

static int __init lowmem_init(void)

{

{

	task_handoff_register(&task_nb);

	register_shrinker(&lowmem_shrinker);

	register_shrinker(&lowmem_shrinker);

	return 0;

	return 0;

}

}
@@ -206,7 +173,6 @@ static int __init lowmem_init(void) 
static void __exit lowmem_exit(void)

static void __exit lowmem_exit(void)

{

{

	unregister_shrinker(&lowmem_shrinker);

	unregister_shrinker(&lowmem_shrinker);

	task_handoff_unregister(&task_nb);

}

}





module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);

module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);