2012-06-22 21:44:38

by David Rientjes

Subject: [patch 3.5-rc3] mm, oom: fix potential killing of thread that is disabled from oom killing

/proc/sys/vm/oom_kill_allocating_task will immediately kill current when
the oom killer is called to avoid a potentially expensive tasklist scan
for large systems.

Currently, however, it is not checking current's oom_score_adj value
which may be OOM_SCORE_ADJ_MIN, meaning that it has been disabled from
oom killing.

This patch avoids killing current in such a condition and simply falls
back to the tasklist scan since memory still needs to be freed.

Signed-off-by: David Rientjes <[email protected]>
---
mm/oom_kill.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -720,9 +720,9 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);

read_lock(&tasklist_lock);
- if (sysctl_oom_kill_allocating_task &&
+ if (sysctl_oom_kill_allocating_task && current->mm &&
!oom_unkillable_task(current, NULL, nodemask) &&
- current->mm) {
+ current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
nodemask,
"Out of memory (oom_kill_allocating_task)");

2012-06-22 23:03:17

by KOSAKI Motohiro

Subject: Re: [patch 3.5-rc3] mm, oom: fix potential killing of thread that is disabled from oom killing

On Fri, Jun 22, 2012 at 5:44 PM, David Rientjes <[email protected]> wrote:
> /proc/sys/vm/oom_kill_allocating_task will immediately kill current when
> the oom killer is called to avoid a potentially expensive tasklist scan
> for large systems.
>
> Currently, however, it is not checking current's oom_score_adj value
> which may be OOM_SCORE_ADJ_MIN, meaning that it has been disabled from
> oom killing.
>
> This patch avoids killing current in such a condition and simply falls
> back to the tasklist scan since memory still needs to be freed.
>
> Signed-off-by: David Rientjes <[email protected]>
> ---
> ?mm/oom_kill.c | ? ?4 ++--
> ?1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -720,9 +720,9 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
> ? ? ? ?check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
>
> ? ? ? ?read_lock(&tasklist_lock);
> - ? ? ? if (sysctl_oom_kill_allocating_task &&
> + ? ? ? if (sysctl_oom_kill_allocating_task && current->mm &&
> ? ? ? ? ? ?!oom_unkillable_task(current, NULL, nodemask) &&
> - ? ? ? ? ? current->mm) {
> + ? ? ? ? ? current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
> ? ? ? ? ? ? ? ?oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? nodemask,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "Out of memory (oom_kill_allocating_task)");

Seems straight forward and reasonable.

Acked-by: KOSAKI Motohiro <[email protected]>