From dc9f14036f2db72633dcf8e6602c6ba6a30e7cd9 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Wed, 5 Oct 2011 11:42:49 +1100 Subject: [PATCH] oom: remove oom_disable_count 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 Cc: Ying Han Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton --- fs/exec.c | 4 ---- fs/proc/base.c | 13 ------------- include/linux/mm_types.h | 3 --- kernel/exit.c | 2 -- kernel/fork.c | 10 +--------- mm/oom_kill.c | 23 +++++------------------ 6 files changed, 6 insertions(+), 49 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 8433e5de1c70..8002e7d1ae91 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -841,10 +841,6 @@ static int exec_mmap(struct mm_struct *mm) tsk->mm = mm; tsk->active_mm = mm; activate_mm(active_mm, mm); - if (old_mm && tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) { - atomic_dec(&old_mm->oom_disable_count); - atomic_inc(&tsk->mm->oom_disable_count); - } task_unlock(tsk); arch_pick_mmap_layout(mm); if (old_mm) { diff --git a/fs/proc/base.c b/fs/proc/base.c index 5eb02069e1b8..8f0087e20e16 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1107,13 +1107,6 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf, goto err_sighand; } - if (oom_adjust != task->signal->oom_adj) { - if (oom_adjust == OOM_DISABLE) - atomic_inc(&task->mm->oom_disable_count); - if (task->signal->oom_adj == OOM_DISABLE) - atomic_dec(&task->mm->oom_disable_count); - } - /* * Warn that /proc/pid/oom_adj is deprecated, see * Documentation/feature-removal-schedule.txt. @@ -1215,12 +1208,6 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, goto err_sighand; } - if (oom_score_adj != task->signal->oom_score_adj) { - if (oom_score_adj == OOM_SCORE_ADJ_MIN) - atomic_inc(&task->mm->oom_disable_count); - if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) - atomic_dec(&task->mm->oom_disable_count); - } task->signal->oom_score_adj = oom_score_adj; if (has_capability_noaudit(current, CAP_SYS_RESOURCE)) task->signal->oom_score_adj_min = oom_score_adj; diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 7870e473033c..707c2b1999e2 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -325,9 +325,6 @@ struct mm_struct { unsigned int token_priority; unsigned int last_interval; - /* How many tasks sharing this mm are OOM_DISABLE */ - atomic_t oom_disable_count; - unsigned long flags; /* Must use atomic bitops to access the bits */ struct core_state *core_state; /* coredumping support */ diff --git a/kernel/exit.c b/kernel/exit.c index af36b06305b2..7c8624c06efc 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -682,8 +682,6 @@ static void exit_mm(struct task_struct * tsk) enter_lazy_tlb(mm, current); /* We don't want this task to be frozen prematurely */ clear_freeze_flag(tsk); - if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) - atomic_dec(&mm->oom_disable_count); task_unlock(tsk); mm_update_next_owner(mm); mmput(mm); diff --git a/kernel/fork.c b/kernel/fork.c index bb970564119d..89236dd93f5f 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -502,7 +502,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) mm->cached_hole_size = ~0UL; mm_init_aio(mm); mm_init_owner(mm, p); - atomic_set(&mm->oom_disable_count, 0); if (likely(!mm_alloc_pgd(mm))) { mm->def_flags = 0; @@ -845,8 +844,6 @@ good_mm: /* Initializing for Swap token stuff */ mm->token_priority = 0; mm->last_interval = 0; - if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) - atomic_inc(&mm->oom_disable_count); tsk->mm = mm; tsk->active_mm = mm; @@ -1422,13 +1419,8 @@ bad_fork_cleanup_io: bad_fork_cleanup_namespaces: exit_task_namespaces(p); bad_fork_cleanup_mm: - if (p->mm) { - task_lock(p); - if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) - atomic_dec(&p->mm->oom_disable_count); - task_unlock(p); + if (p->mm) mmput(p->mm); - } bad_fork_cleanup_signal: if (!(clone_flags & CLONE_THREAD)) free_signal_struct(p->signal); diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 64bccffb848e..d25a3da9a8a7 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -53,13 +53,7 @@ int test_set_oom_score_adj(int new_val) spin_lock_irq(&sighand->siglock); old_val = current->signal->oom_score_adj; - if (new_val != old_val) { - if (new_val == OOM_SCORE_ADJ_MIN) - atomic_inc(¤t->mm->oom_disable_count); - else if (old_val == OOM_SCORE_ADJ_MIN) - atomic_dec(¤t->mm->oom_disable_count); - current->signal->oom_score_adj = new_val; - } + current->signal->oom_score_adj = new_val; spin_unlock_irq(&sighand->siglock); return old_val; @@ -171,16 +165,6 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, if (!p) return 0; - /* - * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN - * so the entire heuristic doesn't need to be executed for something - * that cannot be killed. - */ - if (atomic_read(&p->mm->oom_disable_count)) { - task_unlock(p); - return 0; - } - /* * The memory controller may have a limit of 0 bytes, so avoid a divide * by zero, if necessary. @@ -447,6 +431,9 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem) for_each_process(q) if (q->mm == mm && !same_thread_group(q, p) && !(q->flags & PF_KTHREAD)) { + if (q->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) + continue; + task_lock(q); /* Protect ->comm from prctl() */ pr_err("Kill process %d (%s) sharing same memory\n", task_pid_nr(q), q->comm); @@ -723,7 +710,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, read_lock(&tasklist_lock); if (sysctl_oom_kill_allocating_task && !oom_unkillable_task(current, NULL, nodemask) && - current->mm && !atomic_read(¤t->mm->oom_disable_count)) { + current->mm) { /* * oom_kill_process() needs tasklist_lock held. If it returns * non-zero, current could not be killed so we must fallback to -- 2.39.5