From d75da004c708c9fca7b53f7da293a295522414d9 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 3 May 2017 14:54:57 -0700 Subject: [PATCH] oom: improve oom disable handling 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@kernel.org Signed-off-by: Michal Hocko Reported-by: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/tty/sysrq.c | 2 +- mm/oom_kill.c | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 677f0ddc986c..3ffc1ce29023 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -372,7 +372,7 @@ static void moom_callback(struct work_struct *ignored) 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); } diff --git a/mm/oom_kill.c b/mm/oom_kill.c index d083714a2bb9..04c9143a8625 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -685,6 +685,7 @@ void exit_oom_victim(void) void oom_killer_enable(void) { oom_killer_disabled = false; + pr_info("OOM killer enabled.\n"); } /** @@ -721,6 +722,7 @@ bool oom_killer_disable(signed long timeout) oom_killer_enable(); return false; } + pr_info("OOM killer disabled.\n"); return true; }