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[PATCH] oom-kill: mm locking fix

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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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andrew Morton 2006-04-18 22:20:38 -07:00 committed by Linus Torvalds
parent 75129e297e
commit 97c2c9b84d
1 changed files with 18 additions and 8 deletions
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26
mm/oom_kill.c
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@ -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);
}
/*