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Commit 97c2c9b8 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
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[PATCH] oom-kill: mm locking fix 



Dave Peterson <dsp@llnl.gov> points out that badness() is playing with
mm_structs without taking a reference on them.

mmput() can sleep, so taking a reference here (inside tasklist_lock) is
hard.  Fix it up via task_lock() instead.

Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 75129e29

mm/oom_kill.c

+18 −8
Original line number Diff line number Diff line
@@ -46,15 +46,25 @@ 
unsigned long badness(struct task_struct *p, unsigned long uptime)

{

	unsigned long points, cpu_time, run_time, s;

	struct list_head *tsk;

	struct mm_struct *mm;

	struct task_struct *child;



	if (!p->mm)

	task_lock(p);

	mm = p->mm;

	if (!mm) {

		task_unlock(p);

		return 0;

	}



	/*

	 * The memory size of the process is the basis for the badness.

	 */

	points = p->mm->total_vm;

	points = mm->total_vm;



	/*

	 * After this unlock we can no longer dereference local variable `mm'

	 */

	task_unlock(p);



	/*

	 * Processes which fork a lot of child processes are likely
@@ -64,11 +74,11 @@ unsigned long badness(struct task_struct *p, unsigned long uptime) 
	 * child is eating the vast majority of memory, adding only half

	 * to the parents will make the child our kill candidate of choice.

	 */

	list_for_each(tsk, &p->children) {

		struct task_struct *chld;

		chld = list_entry(tsk, struct task_struct, sibling);

		if (chld->mm != p->mm && chld->mm)

			points += chld->mm->total_vm/2 + 1;

	list_for_each_entry(child, &p->children, sibling) {

		task_lock(child);

		if (child->mm != mm && child->mm)

			points += child->mm->total_vm/2 + 1;

		task_unlock(child);

	}



	/*