Merge git://git.linux-nfs.org/pub/linux/nfs-2.6

[pandora-kernel.git] / mm / oom_kill.c

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 8123fad..042e643 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -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);
        }
 
        /*
@@ -244,17 +254,24 @@ static void __oom_kill_task(task_t *p, const char *message)
        force_sig(SIGKILL, p);
 }
 
-static struct mm_struct *oom_kill_task(task_t *p, const char *message)
+static int oom_kill_task(task_t *p, const char *message)
 {
-       struct mm_struct *mm = get_task_mm(p);
+       struct mm_struct *mm;
        task_t * g, * q;
 
-       if (!mm)
-               return NULL;
-       if (mm == &init_mm) {
-               mmput(mm);
-               return NULL;
-       }
+       mm = p->mm;
+
+       /* WARNING: mm may not be dereferenced since we did not obtain its
+        * value from get_task_mm(p).  This is OK since all we need to do is
+        * compare mm to q->mm below.
+        *
+        * Furthermore, even if mm contains a non-NULL value, p->mm may
+        * change to NULL at any time since we do not hold task_lock(p).
+        * However, this is of no concern to us.
+        */
+
+       if (mm == NULL || mm == &init_mm)
+               return 1;
 
        __oom_kill_task(p, message);
        /*
@@ -266,13 +283,12 @@ static struct mm_struct *oom_kill_task(task_t *p, const char *message)
                        __oom_kill_task(q, message);
        while_each_thread(g, q);
 
-       return mm;
+       return 0;
 }
 
-static struct mm_struct *oom_kill_process(struct task_struct *p,
-                               unsigned long points, const char *message)
+static int oom_kill_process(struct task_struct *p, unsigned long points,
+               const char *message)
 {
-       struct mm_struct *mm;
        struct task_struct *c;
        struct list_head *tsk;
 
@@ -283,9 +299,8 @@ static struct mm_struct *oom_kill_process(struct task_struct *p,
                c = list_entry(tsk, struct task_struct, sibling);
                if (c->mm == p->mm)
                        continue;
-               mm = oom_kill_task(c, message);
-               if (mm)
-                       return mm;
+               if (!oom_kill_task(c, message))
+                       return 0;
        }
        return oom_kill_task(p, message);
 }
@@ -300,9 +315,8 @@ static struct mm_struct *oom_kill_process(struct task_struct *p,
  */
 void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
 {
-       struct mm_struct *mm = NULL;
        task_t *p;
-       unsigned long points;
+       unsigned long points = 0;
 
        if (printk_ratelimit()) {
                printk("oom-killer: gfp_mask=0x%x, order=%d\n",
@@ -320,12 +334,12 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
         */
        switch (constrained_alloc(zonelist, gfp_mask)) {
        case CONSTRAINT_MEMORY_POLICY:
-               mm = oom_kill_process(current, points,
+               oom_kill_process(current, points,
                                "No available memory (MPOL_BIND)");
                break;
 
        case CONSTRAINT_CPUSET:
-               mm = oom_kill_process(current, points,
+               oom_kill_process(current, points,
                                "No available memory in cpuset");
                break;
 
@@ -347,22 +361,20 @@ retry:
                        panic("Out of memory and no killable processes...\n");
                }
 
-               mm = oom_kill_process(p, points, "Out of memory");
-               if (!mm)
+               if (oom_kill_process(p, points, "Out of memory"))
                        goto retry;
 
                break;
        }
 
 out:
+       read_unlock(&tasklist_lock);
        cpuset_unlock();
-       if (mm)
-               mmput(mm);
 
        /*
         * Give "p" a good chance of killing itself before we
         * retry to allocate memory unless "p" is current
         */
        if (!test_thread_flag(TIF_MEMDIE))
-               schedule_timeout_interruptible(1);
+               schedule_timeout_uninterruptible(1);
 }