Patch "oom: improve oom disable handling" has been added to the 4.9-stable tree

PATCH [email protected] 2 participants 3 messages Mar 22, 2018

Subsystems (4)

Stable branch Memory management TTY layer and serial drivers Memory management - OOM killer

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2018-03-22 13:51 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

oom: improve oom disable handling

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
oom-improve-oom-disable-handling.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Thu Mar 22 14:40:24 CET 2018

From: Michal Hocko <[email protected]>
Date: Wed, 3 May 2017 14:54:57 -0700
Subject: oom: improve oom disable handling

From: Michal Hocko <[email protected]>

[ 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/[email protected] open here

Signed-off-by Michal Hocko <[email protected]>

Reported-by Tetsuo Handa <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 drivers/tty/sysrq.c |    2 +-
 mm/oom_kill.c       |    2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

drivers/tty/sysrq.c +1 -1

@@ -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);
 }

mm/oom_kill.c +2 -0

@@ -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 [email protected] 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

2018-03-22 14:16 UTC #1 lore raw

Greg, this doesn't really look like a fix that should go to the stable tree. It doesn't really fix any serious bug.

Quoted 85 lines · Greg KH

Quoted 1 line
From foo@baz Thu Mar 22 14:40:24 CET 2018
From: Michal Hocko <[email protected]>
Date: Wed, 3 May 2017 14:54:57 -0700
Subject: oom: improve oom disable handling
From: Michal Hocko <[email protected]>
[ 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/[email protected] open here
Signed-off-by Michal Hocko <[email protected]>
Reported-by Tetsuo Handa <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/tty/sysrq.c |    2 +-
 mm/oom_kill.c       |    2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)
drivers/tty/sysrq.c +1 -1
@@ -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);
 }
 
mm/oom_kill.c +2 -0
@@ -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 [email protected] 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

Signature · 2 lines

Michal Hocko
SUSE Labs

Greg KH

author maintainer

2018-03-22 14:48 UTC #2 lore raw

Quoted 2 lines · Michal Hocko

Greg, this doesn't really look like a fix that should go to the stable tree. It doesn't really fix any serious bug.

Thanks for letting me know, now dropped.

greg k-h