Greg, this doesn't really look like a fix that should go to the stable
tree. It doesn't really fix any serious bug.
On Thu 22-03-18 14:49:48, Greg KH wrote:
> >From foo@baz Thu Mar 22 14:40:24 CET 2018
> From: Michal Hocko <mhocko@xxxxxxxx>
> Date: Wed, 3 May 2017 14:54:57 -0700
> Subject: oom: improve oom disable handling
>
> From: Michal Hocko <mhocko@xxxxxxxx>
>
>
> [ Upstream commit d75da004c708c9fca7b53f7da293a295522414d9 ]
>
> Tetsuo has reported that sysrq triggered OOM killer will print a
> misleading information when no tasks are selected:
>
> sysrq: SysRq : Manual OOM execution
> Out of memory: Kill process 4468 ((agetty)) score 0 or sacrifice child
> Killed process 4468 ((agetty)) total-vm:43704kB, anon-rss:1760kB, file-rss:0kB, shmem-rss:0kB
> sysrq: SysRq : Manual OOM execution
> Out of memory: Kill process 4469 (systemd-cgroups) score 0 or sacrifice child
> Killed process 4469 (systemd-cgroups) total-vm:10704kB, anon-rss:120kB, file-rss:0kB, shmem-rss:0kB
> sysrq: SysRq : Manual OOM execution
> sysrq: OOM request ignored because killer is disabled
> sysrq: SysRq : Manual OOM execution
> sysrq: OOM request ignored because killer is disabled
> sysrq: SysRq : Manual OOM execution
> sysrq: OOM request ignored because killer is disabled
>
> The real reason is that there are no eligible tasks for the OOM killer
> to select but since commit 7c5f64f84483 ("mm: oom: deduplicate victim
> selection code for memcg and global oom") the semantic of out_of_memory
> has changed without updating moom_callback.
>
> This patch updates moom_callback to tell that no task was eligible which
> is the case for both oom killer disabled and no eligible tasks. In
> order to help distinguish first case from the second add printk to both
> oom_killer_{enable,disable}. This information is useful on its own
> because it might help debugging potential memory allocation failures.
>
> Fixes: 7c5f64f84483 ("mm: oom: deduplicate victim selection code for memcg and global oom")
> Link: http://lkml.kernel.org/r/20170404134705.6361-1-mhocko@xxxxxxxxxx
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/tty/sysrq.c | 2 +-
> mm/oom_kill.c | 2 ++
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -375,7 +375,7 @@ static void moom_callback(struct work_st
>
> mutex_lock(&oom_lock);
> if (!out_of_memory(&oc))
> - pr_info("OOM request ignored because killer is disabled\n");
> + pr_info("OOM request ignored. No task eligible\n");
> mutex_unlock(&oom_lock);
> }
>
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -706,6 +706,7 @@ void exit_oom_victim(void)
> void oom_killer_enable(void)
> {
> oom_killer_disabled = false;
> + pr_info("OOM killer enabled.\n");
> }
>
> /**
> @@ -742,6 +743,7 @@ bool oom_killer_disable(signed long time
> oom_killer_enable();
> return false;
> }
> + pr_info("OOM killer disabled.\n");
>
> return true;
> }
>
>
> Patches currently in stable-queue which might be from mhocko@xxxxxxxx are
>
> queue-4.9/mm-fix-check-for-reclaimable-pages-in-pf_memalloc-reclaim-throttling.patch
> queue-4.9/oom-improve-oom-disable-handling.patch
--
Michal Hocko
SUSE Labs