path: root/mm/oom_kill.c
diff options
authorDavid Rientjes <rientjes@google.com>2012-12-11 16:02:56 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-11 17:22:27 -0800
commite1e12d2f3104be886073ac6c5c4678f30b1b9e51 (patch)
treeb08cba1dba28e18cf7c2ffd8d076ce744e368b5f /mm/oom_kill.c
parenta9c58b907dbc6821533dfc295b63caf111ff1f16 (diff)
mm, oom: fix race when specifying a thread as the oom origin
test_set_oom_score_adj() and compare_swap_oom_score_adj() are used to specify that current should be killed first if an oom condition occurs in between the two calls. The usage is short oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX); ... compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj); to store the thread's oom_score_adj, temporarily change it to the maximum score possible, and then restore the old value if it is still the same. This happens to still be racy, however, if the user writes OOM_SCORE_ADJ_MAX to /proc/pid/oom_score_adj in between the two calls. The compare_swap_oom_score_adj() will then incorrectly reset the old value prior to the write of OOM_SCORE_ADJ_MAX. To fix this, introduce a new oom_flags_t member in struct signal_struct that will be used for per-thread oom killer flags. KSM and swapoff can now use a bit in this member to specify that threads should be killed first in oom conditions without playing around with oom_score_adj. This also allows the correct oom_score_adj to always be shown when reading /proc/pid/oom_score. Signed-off-by: David Rientjes <rientjes@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/oom_kill.c')
1 files changed, 7 insertions, 42 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 37ab4c5ab6e..18f1ae2b45d 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -44,48 +44,6 @@ int sysctl_oom_kill_allocating_task;
int sysctl_oom_dump_tasks = 1;
static DEFINE_SPINLOCK(zone_scan_lock);
- * compare_swap_oom_score_adj() - compare and swap current's oom_score_adj
- * @old_val: old oom_score_adj for compare
- * @new_val: new oom_score_adj for swap
- *
- * Sets the oom_score_adj value for current to @new_val iff its present value is
- * @old_val. Usually used to reinstate a previous value to prevent racing with
- * userspacing tuning the value in the interim.
- */
-void compare_swap_oom_score_adj(short old_val, short new_val)
- struct sighand_struct *sighand = current->sighand;
- spin_lock_irq(&sighand->siglock);
- if (current->signal->oom_score_adj == old_val)
- current->signal->oom_score_adj = new_val;
- trace_oom_score_adj_update(current);
- spin_unlock_irq(&sighand->siglock);
- * test_set_oom_score_adj() - set current's oom_score_adj and return old value
- * @new_val: new oom_score_adj value
- *
- * Sets the oom_score_adj value for current to @new_val with proper
- * synchronization and returns the old value. Usually used to temporarily
- * set a value, save the old value in the caller, and then reinstate it later.
- */
-short test_set_oom_score_adj(short new_val)
- struct sighand_struct *sighand = current->sighand;
- int old_val;
- spin_lock_irq(&sighand->siglock);
- old_val = current->signal->oom_score_adj;
- current->signal->oom_score_adj = new_val;
- trace_oom_score_adj_update(current);
- spin_unlock_irq(&sighand->siglock);
- return old_val;
* has_intersects_mems_allowed() - check task eligiblity for kill
@@ -310,6 +268,13 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
if (!task->mm)
+ /*
+ * If task is allocating a lot of memory and has been marked to be
+ * killed first if it triggers an oom, then select it.
+ */
+ if (oom_task_origin(task))
if (task->flags & PF_EXITING && !force_kill) {
* If this task is not being ptraced on exit, then wait for it