- 08 10月, 2016 3 次提交
-
-
由 Tetsuo Handa 提交于
Patch series "fortify oom killer even more", v2. This patch (of 9): __oom_reap_task() can be simplified a bit if it receives a valid mm from oom_reap_task() which also uses that mm when __oom_reap_task() failed. We can drop one find_lock_task_mm() call and also make the __oom_reap_task() code flow easier to follow. Moreover, this will make later patch in the series easier to review. Pinning mm's mm_count for longer time is not really harmful because this will not pin much memory. This patch doesn't introduce any functional change. Link: http://lkml.kernel.org/r/1472119394-11342-2-git-send-email-mhocko@kernel.orgSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Vladimir Davydov <vdavydov@parallels.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
Attempt to demystify the task_will_free_mem() loop. Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Vladimir Davydov 提交于
When selecting an oom victim, we use the same heuristic for both memory cgroup and global oom. The only difference is the scope of tasks to select the victim from. So we could just export an iterator over all memcg tasks and keep all oom related logic in oom_kill.c, but instead we duplicate pieces of it in memcontrol.c reusing some initially private functions of oom_kill.c in order to not duplicate all of it. That looks ugly and error prone, because any modification of select_bad_process should also be propagated to mem_cgroup_out_of_memory. Let's rework this as follows: keep all oom heuristic related code private to oom_kill.c and make oom_kill.c use exported memcg functions when it's really necessary (like in case of iterating over memcg tasks). Link: http://lkml.kernel.org/r/1470056933-7505-1-git-send-email-vdavydov@virtuozzo.comSigned-off-by: NVladimir Davydov <vdavydov@virtuozzo.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 12 8月, 2016 1 次提交
-
-
由 Geert Uytterhoeven 提交于
mm/oom_kill.c: In function `task_will_free_mem': mm/oom_kill.c:767: warning: `ret' may be used uninitialized in this function If __task_will_free_mem() is never called inside the for_each_process() loop, ret will not be initialized. Fixes: 1af8bb43 ("mm, oom: fortify task_will_free_mem()") Link: http://lkml.kernel.org/r/1470255599-24841-1-git-send-email-geert@linux-m68k.orgSigned-off-by: NGeert Uytterhoeven <geert@linux-m68k.org> Acked-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 29 7月, 2016 8 次提交
-
-
由 Michal Hocko 提交于
"mm, oom: fortify task_will_free_mem" has dropped task_lock around task_will_free_mem in oom_kill_process bacause it assumed that a potential race when the selected task exits will not be a problem as the oom_reaper will call exit_oom_victim. Tetsuo was objecting that nommu doesn't have oom_reaper so the race would be still possible. The code would be racy and lockup prone theoretically in other aspects without the oom reaper anyway so I didn't considered this a big deal. But it seems that further changes I am planning in this area will benefit from stable task->mm in this path as well. So let's drop find_lock_task_mm from task_will_free_mem and call it from under task_lock as we did previously. Just pull the task->mm != NULL check inside the function. Link: http://lkml.kernel.org/r/1467201562-6709-1-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
The only case where the oom_reaper is not triggered for the oom victim is when it shares the memory with a kernel thread (aka use_mm) or with the global init. After "mm, oom: skip vforked tasks from being selected" the victim cannot be a vforked task of the global init so we are left with clone(CLONE_VM) (without CLONE_SIGHAND). use_mm() users are quite rare as well. In order to help forward progress for the OOM killer, make sure that this really rare case will not get in the way - we do this by hiding the mm from the oom killer by setting MMF_OOM_REAPED flag for it. oom_scan_process_thread will ignore any TIF_MEMDIE task if it has MMF_OOM_REAPED flag set to catch these oom victims. After this patch we should guarantee forward progress for the OOM killer even when the selected victim is sharing memory with a kernel thread or global init as long as the victims mm is still alive. Link: http://lkml.kernel.org/r/1466426628-15074-11-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
oom_reaper relies on the mmap_sem for read to do its job. Many places which might block readers have been converted to use down_write_killable and that has reduced chances of the contention a lot. Some paths where the mmap_sem is held for write can take other locks and they might either be not prepared to fail due to fatal signal pending or too impractical to be changed. This patch introduces MMF_OOM_NOT_REAPABLE flag which gets set after the first attempt to reap a task's mm fails. If the flag is present after the failure then we set MMF_OOM_REAPED to hide this mm from the oom killer completely so it can go and chose another victim. As a result a risk of OOM deadlock when the oom victim would be blocked indefinetly and so the oom killer cannot make any progress should be mitigated considerably while we still try really hard to perform all reclaim attempts and stay predictable in the behavior. Link: http://lkml.kernel.org/r/1466426628-15074-10-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
The 0-day robot has encountered the following: Out of memory: Kill process 3914 (trinity-c0) score 167 or sacrifice child Killed process 3914 (trinity-c0) total-vm:55864kB, anon-rss:1512kB, file-rss:1088kB, shmem-rss:25616kB oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26488kB oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26900kB oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26900kB oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:27296kB oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:28148kB oom_reaper is trying to reap the same task again and again. This is possible only when the oom killer is bypassed because of task_will_free_mem because we skip over tasks with MMF_OOM_REAPED already set during select_bad_process. Teach task_will_free_mem to skip over MMF_OOM_REAPED tasks as well because they will be unlikely to free anything more. Analyzed by Tetsuo Handa. Link: http://lkml.kernel.org/r/1466426628-15074-9-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
task_will_free_mem is rather weak. It doesn't really tell whether the task has chance to drop its mm. 98748bd7 ("oom: consider multi-threaded tasks in task_will_free_mem") made a first step into making it more robust for multi-threaded applications so now we know that the whole process is going down and probably drop the mm. This patch builds on top for more complex scenarios where mm is shared between different processes - CLONE_VM without CLONE_SIGHAND, or in kernel use_mm(). Make sure that all processes sharing the mm are killed or exiting. This will allow us to replace try_oom_reaper by wake_oom_reaper because task_will_free_mem implies the task is reapable now. Therefore all paths which bypass the oom killer are now reapable and so they shouldn't lock up the oom killer. Link: http://lkml.kernel.org/r/1466426628-15074-8-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
Currently oom_kill_process skips both the oom reaper and SIG_KILL if a process sharing the same mm is unkillable via OOM_ADJUST_MIN. After "mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj" all such processes are sharing the same value so we shouldn't see such a task at all (oom_badness would rule them out). We can still encounter oom disabled vforked task which has to be killed as well if we want to have other tasks sharing the mm reapable because it can access the memory before doing exec. Killing such a task should be acceptable because it is highly unlikely it has done anything useful because it cannot modify any memory before it calls exec. An alternative would be to keep the task alive and skip the oom reaper and risk all the weird corner cases where the OOM killer cannot make forward progress because the oom victim hung somewhere on the way to exit. [rientjes@google.com - drop printk when OOM_SCORE_ADJ_MIN killed task the setting is inherently racy and we cannot do much about it without introducing locks in hot paths] Link: http://lkml.kernel.org/r/1466426628-15074-7-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
vforked tasks are not really sitting on any memory. They are sharing the mm with parent until they exec into a new code. Until then it is just pinning the address space. OOM killer will kill the vforked task along with its parent but we still can end up selecting vforked task when the parent wouldn't be selected. E.g. init doing vfork to launch a task or vforked being a child of oom unkillable task with an updated oom_score_adj to be killable. Add a new helper to check whether a task is in the vfork sharing memory with its parent and use it in oom_badness to skip over these tasks. Link: http://lkml.kernel.org/r/1466426628-15074-6-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
oom_score_adj is shared for the thread groups (via struct signal) but this is not sufficient to cover processes sharing mm (CLONE_VM without CLONE_SIGHAND) and so we can easily end up in a situation when some processes update their oom_score_adj and confuse the oom killer. In the worst case some of those processes might hide from the oom killer altogether via OOM_SCORE_ADJ_MIN while others are eligible. OOM killer would then pick up those eligible but won't be allowed to kill others sharing the same mm so the mm wouldn't release the mm and so the memory. It would be ideal to have the oom_score_adj per mm_struct because that is the natural entity OOM killer considers. But this will not work because some programs are doing vfork() set_oom_adj() exec() We can achieve the same though. oom_score_adj write handler can set the oom_score_adj for all processes sharing the same mm if the task is not in the middle of vfork. As a result all the processes will share the same oom_score_adj. The current implementation is rather pessimistic and checks all the existing processes by default if there is more than 1 holder of the mm but we do not have any reliable way to check for external users yet. Link: http://lkml.kernel.org/r/1466426628-15074-5-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NOleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 27 7月, 2016 4 次提交
-
-
由 Michal Hocko 提交于
Tetsuo is worried that mmput_async might still lead to a premature new oom victim selection due to the following race: __oom_reap_task exit_mm find_lock_task_mm atomic_inc(mm->mm_users) # = 2 task_unlock task_lock task->mm = NULL up_read(&mm->mmap_sem) < somebody write locks mmap_sem > task_unlock mmput atomic_dec_and_test # = 1 exit_oom_victim down_read_trylock # failed - no reclaim mmput_async # Takes unpredictable amount of time < new OOM situation > the final __mmput will be executed in the delayed context which might happen far in the future. Such a race is highly unlikely because the write holder of mmap_sem would have to be an external task (all direct holders are already killed or exiting) and it usually have to pin mm_users in order to do anything reasonable. We can, however, make sure that the mmput_async is only called when we do not back off and reap some memory. That would reduce the impact of the delayed __mmput because the real content would be already freed. Pin mm_count to keep it alive after we drop task_lock and before we try to get mmap_sem. If the mmap_sem succeeds we can try to grab mm_users reference and then go on with unmapping the address space. It is not clear whether this race is possible at all but it is better to be more robust and do not pin mm_users unless we are sure we are actually doing some real work during __oom_reap_task. Link: http://lkml.kernel.org/r/1465306987-30297-1-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Tetsuo Handa 提交于
oom_scan_process_thread() does not use totalpages argument. oom_badness() uses it. Link: http://lkml.kernel.org/r/1463796041-7889-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jpSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: NMichal Hocko <mhocko@suse.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Vladimir Davydov 提交于
It's a part of oom context just like allocation order and nodemask, so let's move it to oom_control instead of passing it in the argument list. Link: http://lkml.kernel.org/r/40e03fd7aaf1f55c75d787128d6d17c5a71226c2.1464358556.git.vdavydov@virtuozzo.comSigned-off-by: NVladimir Davydov <vdavydov@virtuozzo.com> Acked-by: NMichal Hocko <mhocko@suse.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Vladimir Davydov 提交于
Not used since oom_lock was instroduced. Link: http://lkml.kernel.org/r/1464358093-22663-1-git-send-email-vdavydov@virtuozzo.comSigned-off-by: NVladimir Davydov <vdavydov@virtuozzo.com> Acked-by: NMichal Hocko <mhocko@suse.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 25 6月, 2016 2 次提交
-
-
由 Tetsuo Handa 提交于
Since commit 36324a99 ("oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space") changed to use find_lock_task_mm() for finding a mm_struct to reap, it is guaranteed that mm->mm_users > 0 because find_lock_task_mm() returns a task_struct with ->mm != NULL. Therefore, we can safely use atomic_inc(). Link: http://lkml.kernel.org/r/1465024759-8074-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jpSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Tetsuo Handa 提交于
Commit e2fe1456 ("oom_reaper: close race with exiting task") reduced frequency of needlessly selecting next OOM victim, but was calling mmput_async() when atomic_inc_not_zero() failed. Link: http://lkml.kernel.org/r/1464423365-5555-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jpSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 04 6月, 2016 1 次提交
-
-
由 Michal Hocko 提交于
Oleg has noted that siglock usage in try_oom_reaper is both pointless and dangerous. signal_group_exit can be checked lockless. The problem is that sighand becomes NULL in __exit_signal so we can crash. Fixes: 3ef22dff ("oom, oom_reaper: try to reap tasks which skip regular OOM killer path") Link: http://lkml.kernel.org/r/1464679423-30218-1-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Suggested-by: NOleg Nesterov <oleg@redhat.com> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 28 5月, 2016 2 次提交
-
-
由 Michal Hocko 提交于
Tetsuo has reported: Out of memory: Kill process 443 (oleg's-test) score 855 or sacrifice child Killed process 443 (oleg's-test) total-vm:493248kB, anon-rss:423880kB, file-rss:4kB, shmem-rss:0kB sh invoked oom-killer: gfp_mask=0x24201ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD), order=0, oom_score_adj=0 sh cpuset=/ mems_allowed=0 CPU: 2 PID: 1 Comm: sh Not tainted 4.6.0-rc7+ #51 Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013 Call Trace: dump_stack+0x85/0xc8 dump_header+0x5b/0x394 oom_reaper: reaped process 443 (oleg's-test), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB In other words: __oom_reap_task exit_mm atomic_inc_not_zero tsk->mm = NULL mmput atomic_dec_and_test # > 0 exit_oom_victim # New victim will be # selected <OOM killer invoked> # no TIF_MEMDIE task so we can select a new one unmap_page_range # to release the memory The race exists even without the oom_reaper because anybody who pins the address space and gets preempted might race with exit_mm but oom_reaper made this race more probable. We can address the oom_reaper part by using oom_lock for __oom_reap_task because this would guarantee that a new oom victim will not be selected if the oom reaper might race with the exit path. This doesn't solve the original issue, though, because somebody else still might be pinning mm_users and so __mmput won't be called to release the memory but that is not really realiably solvable because the task will get away from the oom sight as soon as it is unhashed from the task_list and so we cannot guarantee a new victim won't be selected. [akpm@linux-foundation.org: fix use of unused `mm', Per Stephen] [akpm@linux-foundation.org: coding-style fixes] Fixes: aac45363 ("mm, oom: introduce oom reaper") Link: http://lkml.kernel.org/r/1464271493-20008-1-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com> Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Vladimir Davydov 提交于
If the current process is exiting, we don't invoke oom killer, instead we give it access to memory reserves and try to reap its mm in case nobody is going to use it. There's a mistake in the code performing this check - we just ignore any process of the same thread group no matter if it is exiting or not - see try_oom_reaper. Fix it. Link: http://lkml.kernel.org/r/1464087628-7318-1-git-send-email-vdavydov@virtuozzo.com Fixes: 3ef22dff ("oom, oom_reaper: try to reap tasks which skip regular OOM killer path")Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 21 5月, 2016 3 次提交
-
-
由 Tetsuo Handa 提交于
Since commit 3a5dda7a ("oom: prevent unnecessary oom kills or kernel panics"), select_bad_process() is using for_each_process_thread(). Since oom_unkillable_task() scans all threads in the caller's thread group and oom_task_origin() scans signal_struct of the caller's thread group, we don't need to call oom_unkillable_task() and oom_task_origin() on each thread. Also, since !mm test will be done later at oom_badness(), we don't need to do !mm test on each thread. Therefore, we only need to do TIF_MEMDIE test on each thread. Although the original code was correct it was quite inefficient because each thread group was scanned num_threads times which can be a lot especially with processes with many threads. Even though the OOM is extremely cold path it is always good to be as effective as possible when we are inside rcu_read_lock() - aka unpreemptible context. If we track number of TIF_MEMDIE threads inside signal_struct, we don't need to do TIF_MEMDIE test on each thread. This will allow select_bad_process() to use for_each_process(). This patch adds a counter to signal_struct for tracking how many TIF_MEMDIE threads are in a given thread group, and check it at oom_scan_process_thread() so that select_bad_process() can use for_each_process() rather than for_each_process_thread(). [mhocko@suse.com: do not blow the signal_struct size] Link: http://lkml.kernel.org/r/20160520075035.GF19172@dhcp22.suse.cz Link: http://lkml.kernel.org/r/201605182230.IDC73435.MVSOHLFOQFOJtF@I-love.SAKURA.ne.jpSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
Tetsuo has properly noted that mmput slow path might get blocked waiting for another party (e.g. exit_aio waits for an IO). If that happens the oom_reaper would be put out of the way and will not be able to process next oom victim. We should strive for making this context as reliable and independent on other subsystems as much as possible. Introduce mmput_async which will perform the slow path from an async (WQ) context. This will delay the operation but that shouldn't be a problem because the oom_reaper has reclaimed the victim's address space for most cases as much as possible and the remaining context shouldn't bind too much memory anymore. The only exception is when mmap_sem trylock has failed which shouldn't happen too often. The issue is only theoretical but not impossible. Signed-off-by: NMichal Hocko <mhocko@suse.com> Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
Commit 36324a99 ("oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space") not only clears TIF_MEMDIE for oom reaped task but also set OOM_SCORE_ADJ_MIN for the target task to hide it from the oom killer. This works in simple cases but it is not sufficient for (unlikely) cases where the mm is shared between independent processes (as they do not share signal struct). If the mm had only small amount of memory which could be reaped then another task sharing the mm could be selected and that wouldn't help to move out from the oom situation. Introduce MMF_OOM_REAPED mm flag which is checked in oom_badness (same as OOM_SCORE_ADJ_MIN) and task is skipped if the flag is set. Set the flag after __oom_reap_task is done with a task. This will force the select_bad_process() to ignore all already oom reaped tasks as well as no such task is sacrificed for its parent. Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 20 5月, 2016 3 次提交
-
-
由 Michal Hocko 提交于
Right now the oom reaper will clear TIF_MEMDIE only for tasks which were successfully reaped. This is the safest option because we know that such an oom victim would only block forward progress of the oom killer without a good reason because it is highly unlikely it would release much more memory. Basically most of its memory has been already torn down. We can relax this assumption to catch more corner cases though. The first obvious one is when the oom victim clears its mm and gets stuck later on. oom_reaper would back of on find_lock_task_mm returning NULL. We can safely try to clear TIF_MEMDIE in this case because such a task would be ignored by the oom killer anyway. The flag would be cleared by that time already most of the time anyway. The less obvious one is when the oom reaper fails due to mmap_sem contention. Even if we clear TIF_MEMDIE for this task then it is not very likely that we would select another task too easily because we haven't reaped the last victim and so it would be still the #1 candidate. There is a rare race condition possible when the current victim terminates before the next select_bad_process but considering that oom_reap_task had retried several times before giving up then this sounds like a borderline thing. After this patch we should have a guarantee that the OOM killer will not be block for unbounded amount of time for most cases. Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Raushaniya Maksudova <rmaksudova@parallels.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
If either the current task is already killed or PF_EXITING or a selected task is PF_EXITING then the oom killer is suppressed and so is the oom reaper. This patch adds try_oom_reaper which checks the given task and queues it for the oom reaper if that is safe to be done meaning that the task doesn't share the mm with an alive process. This might help to release the memory pressure while the task tries to exit. [akpm@linux-foundation.org: fix nommu build] Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Raushaniya Maksudova <rmaksudova@parallels.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
__alloc_pages_may_oom is the central place to decide when the out_of_memory should be invoked. This is a good approach for most checks there because they are page allocator specific and the allocation fails right after for all of them. The notable exception is GFP_NOFS context which is faking did_some_progress and keep the page allocator looping even though there couldn't have been any progress from the OOM killer. This patch doesn't change this behavior because we are not ready to allow those allocation requests to fail yet (and maybe we will face the reality that we will never manage to safely fail these request). Instead __GFP_FS check is moved down to out_of_memory and prevent from OOM victim selection there. There are two reasons for that - OOM notifiers might release some memory even from this context as none of the registered notifier seems to be FS related - this might help a dying thread to get an access to memory reserves and move on which will make the behavior more consistent with the case when the task gets killed from a different context. Keep a comment in __alloc_pages_may_oom to make sure we do not forget how GFP_NOFS is special and that we really want to do something about it. Note to the current oom_notifier users: The observable difference for you is that oom notifiers cannot depend on any fs locks because we could deadlock. Not that this would be allowed today because that would just lockup machine in most of the cases and ruling out the OOM killer along the way. Another difference is that callbacks might be invoked sooner now because GFP_NOFS is a weaker reclaim context and so there could be reclaimable memory which is just not reachable now. That would require GFP_NOFS only loads which are really rare and more importantly the observable result would be dropping of reconstructible object and potential performance drop which is not such a big deal when we are struggling to fulfill other important allocation requests. Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Raushaniya Maksudova <rmaksudova@parallels.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 02 4月, 2016 1 次提交
-
-
由 Michal Hocko 提交于
Commit bb29902a ("oom, oom_reaper: protect oom_reaper_list using simpler way") has simplified the check for tasks already enqueued for the oom reaper by checking tsk->oom_reaper_list != NULL. This check is not sufficient because the tsk might be the head of the queue without any other tasks queued and then we would simply lockup looping on the same task. Fix the condition by checking for the head as well. Fixes: bb29902a ("oom, oom_reaper: protect oom_reaper_list using simpler way") Signed-off-by: NMichal Hocko <mhocko@suse.com> Acked-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 26 3月, 2016 8 次提交
-
-
由 Tetsuo Handa 提交于
"oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task" tried to protect oom_reaper_list using MMF_OOM_KILLED flag. But we can do it by simply checking tsk->oom_reaper_list != NULL. Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NMichal Hocko <mhocko@suse.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
After "oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space" oom_reaper will call exit_oom_victim on the target task after it is done. This might however race with the PM freezer: CPU0 CPU1 CPU2 freeze_processes try_to_freeze_tasks # Allocation request out_of_memory oom_killer_disable wake_oom_reaper(P1) __oom_reap_task exit_oom_victim(P1) wait_event(oom_victims==0) [...] do_exit(P1) perform IO/interfere with the freezer which breaks the oom_killer_disable semantic. We no longer have a guarantee that the oom victim won't interfere with the freezer because it might be anywhere on the way to do_exit while the freezer thinks the task has already terminated. It might trigger IO or touch devices which are frozen already. In order to close this race, make the oom_reaper thread freezable. This will work because a) already running oom_reaper will block freezer to enter the quiescent state b) wake_oom_reaper will not wake up the reaper after it has been frozen c) the only way to call exit_oom_victim after try_to_freeze_tasks is from the oom victim's context when we know the further interference shouldn't be possible Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Vladimir Davydov 提交于
Entries are only added/removed from oom_reaper_list at head so we can use a single linked list and hence save a word in task_struct. Signed-off-by: NVladimir Davydov <vdavydov@virtuozzo.com> Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
Tetsuo has reported that oom_kill_allocating_task=1 will cause oom_reaper_list corruption because oom_kill_process doesn't follow standard OOM exclusion (aka ignores TIF_MEMDIE) and allows to enqueue the same task multiple times - e.g. by sacrificing the same child multiple times. This patch fixes the issue by introducing a new MMF_OOM_KILLED mm flag which is set in oom_kill_process atomically and oom reaper is disabled if the flag was already set. Signed-off-by: NMichal Hocko <mhocko@suse.com> Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
wake_oom_reaper has allowed only 1 oom victim to be queued. The main reason for that was the simplicity as other solutions would require some way of queuing. The current approach is racy and that was deemed sufficient as the oom_reaper is considered a best effort approach to help with oom handling when the OOM victim cannot terminate in a reasonable time. The race could lead to missing an oom victim which can get stuck out_of_memory wake_oom_reaper cmpxchg // OK oom_reaper oom_reap_task __oom_reap_task oom_victim terminates atomic_inc_not_zero // fail out_of_memory wake_oom_reaper cmpxchg // fails task_to_reap = NULL This race requires 2 OOM invocations in a short time period which is not very likely but certainly not impossible. E.g. the original victim might have not released a lot of memory for some reason. The situation would improve considerably if wake_oom_reaper used a more robust queuing. This is what this patch implements. This means adding oom_reaper_list list_head into task_struct (eat a hole before embeded thread_struct for that purpose) and a oom_reaper_lock spinlock for queuing synchronization. wake_oom_reaper will then add the task on the queue and oom_reaper will dequeue it. Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Andrea Argangeli <andrea@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
Inform about the successful/failed oom_reaper attempts and dump all the held locks to tell us more who is blocking the progress. [akpm@linux-foundation.org: fix CONFIG_MMU=n build] Signed-off-by: NMichal Hocko <mhocko@suse.com> Cc: Andrea Argangeli <andrea@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
When oom_reaper manages to unmap all the eligible vmas there shouldn't be much of the freable memory held by the oom victim left anymore so it makes sense to clear the TIF_MEMDIE flag for the victim and allow the OOM killer to select another task. The lack of TIF_MEMDIE also means that the victim cannot access memory reserves anymore but that shouldn't be a problem because it would get the access again if it needs to allocate and hits the OOM killer again due to the fatal_signal_pending resp. PF_EXITING check. We can safely hide the task from the OOM killer because it is clearly not a good candidate anymore as everyhing reclaimable has been torn down already. This patch will allow to cap the time an OOM victim can keep TIF_MEMDIE and thus hold off further global OOM killer actions granted the oom reaper is able to take mmap_sem for the associated mm struct. This is not guaranteed now but further steps should make sure that mmap_sem for write should be blocked killable which will help to reduce such a lock contention. This is not done by this patch. Note that exit_oom_victim might be called on a remote task from __oom_reap_task now so we have to check and clear the flag atomically otherwise we might race and underflow oom_victims or wake up waiters too early. Signed-off-by: NMichal Hocko <mhocko@suse.com> Suggested-by: NJohannes Weiner <hannes@cmpxchg.org> Suggested-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Andrea Argangeli <andrea@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Michal Hocko 提交于
This patch (of 5): This is based on the idea from Mel Gorman discussed during LSFMM 2015 and independently brought up by Oleg Nesterov. The OOM killer currently allows to kill only a single task in a good hope that the task will terminate in a reasonable time and frees up its memory. Such a task (oom victim) will get an access to memory reserves via mark_oom_victim to allow a forward progress should there be a need for additional memory during exit path. It has been shown (e.g. by Tetsuo Handa) that it is not that hard to construct workloads which break the core assumption mentioned above and the OOM victim might take unbounded amount of time to exit because it might be blocked in the uninterruptible state waiting for an event (e.g. lock) which is blocked by another task looping in the page allocator. This patch reduces the probability of such a lockup by introducing a specialized kernel thread (oom_reaper) which tries to reclaim additional memory by preemptively reaping the anonymous or swapped out memory owned by the oom victim under an assumption that such a memory won't be needed when its owner is killed and kicked from the userspace anyway. There is one notable exception to this, though, if the OOM victim was in the process of coredumping the result would be incomplete. This is considered a reasonable constrain because the overall system health is more important than debugability of a particular application. A kernel thread has been chosen because we need a reliable way of invocation so workqueue context is not appropriate because all the workers might be busy (e.g. allocating memory). Kswapd which sounds like another good fit is not appropriate as well because it might get blocked on locks during reclaim as well. oom_reaper has to take mmap_sem on the target task for reading so the solution is not 100% because the semaphore might be held or blocked for write but the probability is reduced considerably wrt. basically any lock blocking forward progress as described above. In order to prevent from blocking on the lock without any forward progress we are using only a trylock and retry 10 times with a short sleep in between. Users of mmap_sem which need it for write should be carefully reviewed to use _killable waiting as much as possible and reduce allocations requests done with the lock held to absolute minimum to reduce the risk even further. The API between oom killer and oom reaper is quite trivial. wake_oom_reaper updates mm_to_reap with cmpxchg to guarantee only NULL->mm transition and oom_reaper clear this atomically once it is done with the work. This means that only a single mm_struct can be reaped at the time. As the operation is potentially disruptive we are trying to limit it to the ncessary minimum and the reaper blocks any updates while it operates on an mm. mm_struct is pinned by mm_count to allow parallel exit_mmap and a race is detected by atomic_inc_not_zero(mm_users). Signed-off-by: NMichal Hocko <mhocko@suse.com> Suggested-by: NOleg Nesterov <oleg@redhat.com> Suggested-by: NMel Gorman <mgorman@suse.de> Acked-by: NMel Gorman <mgorman@suse.de> Acked-by: NDavid Rientjes <rientjes@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Andrea Argangeli <andrea@kernel.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 18 3月, 2016 3 次提交
-
-
由 Tetsuo Handa 提交于
While oom_killer_disable() is called by freeze_processes() after all user threads except the current thread are frozen, it is possible that kernel threads invoke the OOM killer and sends SIGKILL to the current thread due to sharing the thawed victim's memory. Therefore, checking for SIGKILL is preferable than TIF_MEMDIE. Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: David Rientjes <rientjes@google.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Joe Perches 提交于
Kernel style prefers a single string over split strings when the string is 'user-visible'. Miscellanea: - Add a missing newline - Realign arguments Signed-off-by: NJoe Perches <joe@perches.com> Acked-by: Tejun Heo <tj@kernel.org> [percpu] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
由 Johannes Weiner 提交于
When the OOM killer scans tasks and encounters a PF_EXITING one, it force-selects that task regardless of the score. The problem is that if that task got stuck waiting for some state the allocation site is holding, the OOM reaper can not move on to the next best victim. Frankly, I don't even know why we check for exiting tasks in the OOM killer. We've tried direct reclaim at least 15 times by the time we decide the system is OOM, there was plenty of time to exit and free memory; and a task might exit voluntarily right after we issue a kill. This is testing pure noise. Remove it. Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Andrea Argangeli <andrea@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-
- 16 3月, 2016 1 次提交
-
-
由 Vlastimil Babka 提交于
It would be useful to translate gfp_flags into string representation when printing in case of an OOM, especially as the flags have been undergoing some changes recently and the script ./scripts/gfp-translate needs a matching source version to be accurate. Example output: a.out invoked oom-killer: gfp_mask=0x24280ca(GFP_HIGHUSER_MOVABLE|GFP_ZERO), order=0, om_score_adj=0 Signed-off-by: NVlastimil Babka <vbabka@suse.cz> Acked-by: NMichal Hocko <mhocko@suse.com> Acked-by: NDavid Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
-