linux/mm/oom_kill.c, branch v3.2.38

oom: fix integer overflow of points in oom_badness

2011-12-20T18:25:04Z

An integer overflow will happen on 64bit archs if task's sum of rss, swapents and nr_ptes exceeds (2^31)/1000 value. This was introduced by commit f755a04 oom: use pte pages in OOM score where the oom score computation was divided into several steps and it's no longer computed as one expression in unsigned long(rss, swapents, nr_pte are unsigned long), where the result value assigned to points(int) is in range(1..1000). So there could be an int overflow while computing 176 points *= 1000; and points may have negative value. Meaning the oom score for a mem hog task will be one. 196 if (points <= 0) 197 return 1; For example: [ 3366] 0 3366 35390480 24303939 5 0 0 oom01 Out of memory: Kill process 3366 (oom01) score 1 or sacrifice child Here the oom1 process consumes more than 24303939(rss)*4096~=92GB physical memory, but it's oom score is one. In this situation the mem hog task is skipped and oom killer kills another and most probably innocent task with oom score greater than one. The points variable should be of type long instead of int to prevent the int overflow. Signed-off-by: Frantisek Hrbata Acked-by: KOSAKI Motohiro Acked-by: Oleg Nesterov Acked-by: David Rientjes Cc: [2.6.36+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: do not kill tasks with oom_score_adj OOM_SCORE_ADJ_MIN

2011-11-16T00:41:51Z

Commit c9f01245 ("oom: remove oom_disable_count") has removed the oom_disable_count counter which has been used for early break out from oom_badness so we could never select a task with oom_score_adj set to OOM_SCORE_ADJ_MIN (oom disabled). Now that the counter is gone we are always going through heuristics calculation and we always return a non zero positive value. This means that we can end up killing a task with OOM disabled because it is indistinguishable from regular tasks with 1% resp. CAP_SYS_ADMIN tasks with 3% usage of memory or tasks with oom_score_adj set but OOM enabled. Let's break out early if the task should have OOM disabled. Signed-off-by: Michal Hocko Acked-by: David Rientjes Acked-by: KOSAKI Motohiro Cc: Oleg Nesterov Cc: Ying Han Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux

2011-11-07T03:44:47Z

* 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits) Revert "tracing: Include module.h in define_trace.h" irq: don't put module.h into irq.h for tracking irqgen modules. bluetooth: macroize two small inlines to avoid module.h ip_vs.h: fix implicit use of module_get/module_put from module.h nf_conntrack.h: fix up fallout from implicit moduleparam.h presence include: replace linux/module.h with "struct module" wherever possible include: convert various register fcns to macros to avoid include chaining crypto.h: remove unused crypto_tfm_alg_modname() inline uwb.h: fix implicit use of asm/page.h for PAGE_SIZE pm_runtime.h: explicitly requires notifier.h linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h miscdevice.h: fix up implicit use of lists and types stop_machine.h: fix implicit use of smp.h for smp_processor_id of: fix implicit use of errno.h in include/linux/of.h of_platform.h: delete needless include acpi: remove module.h include from platform/aclinux.h miscdevice.h: delete unnecessary inclusion of module.h device_cgroup.h: delete needless include net: sch_generic remove redundant use of net: inet_timewait_sock doesnt need ... Fix up trivial conflicts (other header files, and removal of the ab3550 mfd driver) in - drivers/media/dvb/frontends/dibx000_common.c - drivers/media/video/{mt9m111.c,ov6650.c} - drivers/mfd/ab3550-core.c - include/linux/dmaengine.h

oom: fix race while temporarily setting current's oom_score_adj

2011-11-01T00:30:45Z

test_set_oom_score_adj() was introduced in 72788c385604 ("oom: replace PF_OOM_ORIGIN with toggling oom_score_adj") to temporarily elevate current's oom_score_adj for ksm and swapoff without requiring an additional per-process flag. Using that function to both set oom_score_adj to OOM_SCORE_ADJ_MAX and then reinstate the previous value is racy since it's possible that userspace can set the value to something else itself before the old value is reinstated. That results in userspace setting current's oom_score_adj to a different value and then the kernel immediately setting it back to its previous value without notification. To fix this, a new compare_swap_oom_score_adj() function is introduced with the same semantics as the compare and swap CAS instruction, or CMPXCHG on x86. It is used to reinstate the previous value of oom_score_adj if and only if the present value is the same as the old value. Signed-off-by: David Rientjes Cc: Oleg Nesterov Cc: Ying Han Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: remove oom_disable_count

2011-11-01T00:30:45Z

This removes mm->oom_disable_count entirely since it's unnecessary and currently buggy. The counter was intended to be per-process but it's currently decremented in the exit path for each thread that exits, causing it to underflow. The count was originally intended to prevent oom killing threads that share memory with threads that cannot be killed since it doesn't lead to future memory freeing. The counter could be fixed to represent all threads sharing the same mm, but it's better to remove the count since: - it is possible that the OOM_DISABLE thread sharing memory with the victim is waiting on that thread to exit and will actually cause future memory freeing, and - there is no guarantee that a thread is disabled from oom killing just because another thread sharing its mm is oom disabled. Signed-off-by: David Rientjes Reported-by: Oleg Nesterov Reviewed-by: Oleg Nesterov Cc: Ying Han Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: avoid killing kthreads if they assume the oom killed thread's mm

2011-11-01T00:30:45Z

After selecting a task to kill, the oom killer iterates all processes and kills all other threads that share the same mm_struct in different thread groups. It would not otherwise be helpful to kill a thread if its memory would not be subsequently freed. A kernel thread, however, may assume a user thread's mm by using use_mm(). This is only temporary and should not result in sending a SIGKILL to that kthread. This patch ensures that only user threads and not kthreads are sent a SIGKILL if they share the same mm_struct as the oom killed task. Signed-off-by: David Rientjes Reviewed-by: Michal Hocko Reviewed-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

oom: thaw threads if oom killed thread is frozen before deferring

2011-11-01T00:30:45Z

If a thread has been oom killed and is frozen, thaw it before returning to the page allocator. Otherwise, it can stay frozen indefinitely and no memory will be freed. Signed-off-by: David Rientjes Reported-by: Konstantin Khlebnikov Cc: Oleg Nesterov Cc: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki Cc: "Rafael J. Wysocki" Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: Map most files to use export.h instead of module.h

2011-10-31T13:20:12Z

The files changed within are only using the EXPORT_SYMBOL macro variants. They are not using core modular infrastructure and hence don't need module.h but only the export.h header. Signed-off-by: Paul Gortmaker

oom: task->mm == NULL doesn't mean the memory was freed

2011-08-02T01:24:12Z

exit_mm() sets ->mm == NULL then it does mmput()->exit_mmap() which frees the memory. However select_bad_process() checks ->mm != NULL before TIF_MEMDIE, so it continues to kill other tasks even if we have the oom-killed task freeing its memory. Change select_bad_process() to check ->mm after TIF_MEMDIE, but skip the tasks which have already passed exit_notify() to ensure a zombie with TIF_MEMDIE set can't block oom-killer. Alternatively we could probably clear TIF_MEMDIE after exit_mmap(). Signed-off-by: Oleg Nesterov Reviewed-by: KOSAKI Motohiro Signed-off-by: Linus Torvalds

oom: remove references to old badness() function

2011-07-26T03:57:09Z

The badness() function in the oom killer was renamed to oom_badness() in a63d83f427fb ("oom: badness heuristic rewrite") since it is a globally exported function for clarity. The prototype for the old function still existed in linux/oom.h, so remove it. There are no existing users. Also fixes documentation and comment references to badness() and adjusts them accordingly. Signed-off-by: David Rientjes Reviewed-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds