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Commit bf4125bb authored by Jim Blackler's avatar Jim Blackler
Browse files

ANDROID: Fixes to locking around handle_lmk_event 



get_task_struct used to reserve 'selected' outside rcu_read_lock block.
Remove the need for get_task_mm, removing the possibility of lock issues there.

Bug: 133479338
Signed-off-by: default avatarJim Blackler <jimblackler@google.com>
Change-Id: I1399e2f669242c04e0e397bc09c987358aa97a0a
parent 1524ee00

drivers/staging/android/lowmemorykiller.c

+8 −12
Original line number Diff line number Diff line
@@ -96,21 +96,15 @@ struct lmk_event { 
	struct list_head list;

};



void handle_lmk_event(struct task_struct *selected, short min_score_adj)

void handle_lmk_event(struct task_struct *selected, int selected_tasksize,

		      short min_score_adj)

{

	int head;

	int tail;

	struct lmk_event *events;

	struct lmk_event *event;

	int res;

	long rss_in_pages = -1;

	char taskname[MAX_TASKNAME];

	struct mm_struct *mm = get_task_mm(selected);



	if (mm) {

		rss_in_pages = get_mm_rss(mm);

		mmput(mm);

	}



	res = get_cmdline(selected, taskname, MAX_TASKNAME - 1);
@@ -149,7 +143,7 @@ void handle_lmk_event(struct task_struct *selected, short min_score_adj) 
	event->maj_flt = selected->maj_flt;

	event->oom_score_adj = selected->signal->oom_score_adj;

	event->start_time = nsec_to_clock_t(selected->real_start_time);

	event->rss_in_pages = rss_in_pages;

	event->rss_in_pages = selected_tasksize;

	event->min_score_adj = min_score_adj;



	event_buffer.head = (head + 1) & (MAX_BUFFERED_EVENTS - 1);
@@ -343,15 +337,17 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc) 
			     free);

		lowmem_deathpending_timeout = jiffies + HZ;

		rem += selected_tasksize;

		get_task_struct(selected);

	}



	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",

		     sc->nr_to_scan, sc->gfp_mask, rem);

	rcu_read_unlock();



	if (selected)

		handle_lmk_event(selected, min_score_adj);



	if (selected) {

		handle_lmk_event(selected, selected_tasksize, min_score_adj);

		put_task_struct(selected);

	}

	return rem;

}