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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#include <linux/oom.h>#include <linux/mm.h>#include <linux/err.h>#include <linux/gfp.h>#include <linux/sched.h>#include <linux/sched/mm.h>#include <linux/sched/task.h>#include <linux/sched/debug.h>#include <linux/swap.h>#include <linux/syscalls.h>#include <linux/timex.h>#include <linux/jiffies.h>#include <linux/cpuset.h>#include <linux/export.h>#include <linux/notifier.h>#include <linux/memcontrol.h>#include <linux/mempolicy.h>#include <linux/security.h>#include <linux/ptrace.h>#include <linux/freezer.h>#include <linux/ftrace.h>#include <linux/ratelimit.h>#include <linux/kthread.h>#include <linux/init.h>#include <linux/mmu_notifier.h>#include <linux/cred.h>#include <linux/nmi.h>
#include <asm/tlb.h>#include "internal.h"#include "slab.h"
#define CREATE_TRACE_POINTS#include <trace/events/oom.h>
static int sysctl_panic_on_oom;static int sysctl_oom_kill_allocating_task;static int sysctl_oom_dump_tasks = 1;
/* * Serializes oom killer invocations (out_of_memory()) from all contexts to * prevent from over eager oom killing (e.g. when the oom killer is invoked * from different domains). * * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled * and mark_oom_victim */DEFINE_MUTEX(oom_lock);/* Serializes oom_score_adj and oom_score_adj_min updates */DEFINE_MUTEX(oom_adj_mutex);
static inline bool is_memcg_oom(struct oom_control *oc){ return oc->memcg != NULL;}
#ifdef CONFIG_NUMA/** * oom_cpuset_eligible() - check task eligibility for kill * @start: task struct of which task to consider * @oc: pointer to struct oom_control * * Task eligibility is determined by whether or not a candidate task, @tsk, * shares the same mempolicy nodes as current if it is bound by such a policy * and whether or not it has the same set of allowed cpuset nodes. * * This function is assuming oom-killer context and 'current' has triggered * the oom-killer. */static bool oom_cpuset_eligible(struct task_struct *start, struct oom_control *oc){ struct task_struct *tsk; bool ret = false; const nodemask_t *mask = oc->nodemask;
rcu_read_lock(); for_each_thread(start, tsk) { if (mask) { /* * If this is a mempolicy constrained oom, tsk's * cpuset is irrelevant. Only return true if its * mempolicy intersects current, otherwise it may be * needlessly killed. */ ret = mempolicy_in_oom_domain(tsk, mask); } else { /* * This is not a mempolicy constrained oom, so only * check the mems of tsk's cpuset. */ ret = cpuset_mems_allowed_intersects(current, tsk); } if (ret) break; } rcu_read_unlock();
return ret;}#elsestatic bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc){ return true;}#endif /* CONFIG_NUMA */
/* * The process p may have detached its own ->mm while exiting or through * kthread_use_mm(), but one or more of its subthreads may still have a valid * pointer. Return p, or any of its subthreads with a valid ->mm, with * task_lock() held. */struct task_struct *find_lock_task_mm(struct task_struct *p){ struct task_struct *t;
guard(rcu)();
for_each_thread(p, t) { task_lock(t); if (likely(t->mm)) return t; task_unlock(t); }
return NULL;}
/* * order == -1 means the oom kill is required by sysrq, otherwise only * for display purposes. */static inline bool is_sysrq_oom(struct oom_control *oc){ return oc->order == -1;}
/* return true if the task is not adequate as candidate victim task. */static bool oom_unkillable_task(struct task_struct *p){ if (is_global_init(p)) return true; if (p->flags & PF_KTHREAD) return true; return false;}
/* * Check whether unreclaimable slab amount is greater than * all user memory(LRU pages). * dump_unreclaimable_slab() could help in the case that * oom due to too much unreclaimable slab used by kernel.*/static bool should_dump_unreclaim_slab(void){ unsigned long nr_lru;
nr_lru = global_node_page_state(NR_ACTIVE_ANON) + global_node_page_state(NR_INACTIVE_ANON) + global_node_page_state(NR_ACTIVE_FILE) + global_node_page_state(NR_INACTIVE_FILE) + global_node_page_state(NR_ISOLATED_ANON) + global_node_page_state(NR_ISOLATED_FILE) + global_node_page_state(NR_UNEVICTABLE);
return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);}
/** * oom_badness - heuristic function to determine which candidate task to kill * @p: task struct of which task we should calculate * @totalpages: total present RAM allowed for page allocation * * The heuristic for determining which task to kill is made to be as simple and * predictable as possible. The goal is to return the highest value for the * task consuming the most memory to avoid subsequent oom failures. */long oom_badness(struct task_struct *p, unsigned long totalpages){ long points; long adj;
if (oom_unkillable_task(p)) return LONG_MIN;
p = find_lock_task_mm(p); if (!p) return LONG_MIN;
/* * Do not even consider tasks which are explicitly marked oom * unkillable or have been already oom reaped or the are in * the middle of vfork */ adj = (long)p->signal->oom_score_adj; if (adj == OOM_SCORE_ADJ_MIN || mm_flags_test(MMF_OOM_SKIP, p->mm) || in_vfork(p)) { task_unlock(p); return LONG_MIN; }
/* * The baseline for the badness score is the proportion of RAM that each * task's rss, pagetable and swap space use. */ points = get_mm_rss_sum(p->mm) + get_mm_counter_sum(p->mm, MM_SWAPENTS) + mm_pgtables_bytes(p->mm) / PAGE_SIZE; task_unlock(p);
/* Normalize to oom_score_adj units */ adj *= totalpages / 1000; points += adj;
return points;}
static const char * const oom_constraint_text[] = { [CONSTRAINT_NONE] = "CONSTRAINT_NONE", [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET", [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY", [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",};
/* * Determine the type of allocation constraint. */static enum oom_constraint constrained_alloc(struct oom_control *oc){ struct zone *zone; struct zoneref *z; enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask); bool cpuset_limited = false; int nid;
if (is_memcg_oom(oc)) { oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1; return CONSTRAINT_MEMCG; }
/* Default to all available memory */ oc->totalpages = totalram_pages() + total_swap_pages;
if (!IS_ENABLED(CONFIG_NUMA)) return CONSTRAINT_NONE;
if (!oc->zonelist) return CONSTRAINT_NONE; /* * Reach here only when __GFP_NOFAIL is used. So, we should avoid * to kill current.We have to random task kill in this case. * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. */ if (oc->gfp_mask & __GFP_THISNODE) return CONSTRAINT_NONE;
/* * This is not a __GFP_THISNODE allocation, so a truncated nodemask in * the page allocator means a mempolicy is in effect. Cpuset policy * is enforced in get_page_from_freelist(). */ if (oc->nodemask && !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) { oc->totalpages = total_swap_pages; for_each_node_mask(nid, *oc->nodemask) oc->totalpages += node_present_pages(nid); return CONSTRAINT_MEMORY_POLICY; }
/* Check this allocation failure is caused by cpuset's wall function */ for_each_zone_zonelist_nodemask(zone, z, oc->zonelist, highest_zoneidx, oc->nodemask) if (!cpuset_zone_allowed(zone, oc->gfp_mask)) cpuset_limited = true;
if (cpuset_limited) { oc->totalpages = total_swap_pages; for_each_node_mask(nid, cpuset_current_mems_allowed) oc->totalpages += node_present_pages(nid); return CONSTRAINT_CPUSET; } return CONSTRAINT_NONE;}
static int oom_evaluate_task(struct task_struct *task, void *arg){ struct oom_control *oc = arg; long points;
if (oom_unkillable_task(task)) goto next;
/* p may not have freeable memory in nodemask */ if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc)) goto next;
/* * This task already has access to memory reserves and is being killed. * Don't allow any other task to have access to the reserves unless * the task has MMF_OOM_SKIP because chances that it would release * any memory is quite low. */ if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) { if (mm_flags_test(MMF_OOM_SKIP, task->signal->oom_mm)) goto next; goto abort; }
/* * If task is allocating a lot of memory and has been marked to be * killed first if it triggers an oom, then select it. */ if (oom_task_origin(task)) { points = LONG_MAX; goto select; }
points = oom_badness(task, oc->totalpages); if (points == LONG_MIN || points < oc->chosen_points) goto next;
select: if (oc->chosen) put_task_struct(oc->chosen); get_task_struct(task); oc->chosen = task; oc->chosen_points = points;next: return 0;abort: if (oc->chosen) put_task_struct(oc->chosen); oc->chosen = (void *)-1UL; return 1;}
/* * Simple selection loop. We choose the process with the highest number of * 'points'. In case scan was aborted, oc->chosen is set to -1. */static void select_bad_process(struct oom_control *oc){ oc->chosen_points = LONG_MIN;
if (is_memcg_oom(oc)) mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc); else { struct task_struct *p;
rcu_read_lock(); for_each_process(p) if (oom_evaluate_task(p, oc)) break; rcu_read_unlock(); }}
static int dump_task(struct task_struct *p, void *arg){ struct oom_control *oc = arg; struct task_struct *task;
if (oom_unkillable_task(p)) return 0;
/* p may not have freeable memory in nodemask */ if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc)) return 0;
task = find_lock_task_mm(p); if (!task) { /* * All of p's threads have already detached their mm's. There's * no need to report them; they can't be oom killed anyway. */ return 0; }
pr_info("[%7d] %5d %5d %8lu %8lu %8lu %8lu %9lu %8ld %8lu %5hd %s\n", task->pid, from_kuid(&init_user_ns, task_uid(task)), task->tgid, task->mm->total_vm, get_mm_rss_sum(task->mm), get_mm_counter_sum(task->mm, MM_ANONPAGES), get_mm_counter_sum(task->mm, MM_FILEPAGES), get_mm_counter_sum(task->mm, MM_SHMEMPAGES), mm_pgtables_bytes(task->mm), get_mm_counter_sum(task->mm, MM_SWAPENTS), task->signal->oom_score_adj, task->comm); task_unlock(task);
return 0;}
/** * dump_tasks - dump current memory state of all system tasks * @oc: pointer to struct oom_control * * Dumps the current memory state of all eligible tasks. Tasks not in the same * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes * are not shown. * State information includes task's pid, uid, tgid, vm size, rss, * pgtables_bytes, swapents, oom_score_adj value, and name. */static void dump_tasks(struct oom_control *oc){ pr_info("Tasks state (memory values in pages):\n"); pr_info("[ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name\n");
if (is_memcg_oom(oc)) mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); else { struct task_struct *p; int i = 0;
rcu_read_lock(); for_each_process(p) { /* Avoid potential softlockup warning */ if ((++i & 1023) == 0) touch_softlockup_watchdog(); dump_task(p, oc); } rcu_read_unlock(); }}
static void dump_oom_victim(struct oom_control *oc, struct task_struct *victim){ /* one line summary of the oom killer context. */ pr_info("oom-kill:constraint=%s,nodemask=%*pbl", oom_constraint_text[oc->constraint], nodemask_pr_args(oc->nodemask)); cpuset_print_current_mems_allowed(); mem_cgroup_print_oom_context(oc->memcg, victim); pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid, from_kuid(&init_user_ns, task_uid(victim)));}
static void dump_header(struct oom_control *oc){ pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%d\n", current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order, current->signal->oom_score_adj); if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order) pr_warn("COMPACTION is disabled!!!\n");
dump_stack(); if (is_memcg_oom(oc)) mem_cgroup_print_oom_meminfo(oc->memcg); else { __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask)); if (should_dump_unreclaim_slab()) dump_unreclaimable_slab(); } mem_cgroup_show_protected_memory(oc->memcg); if (sysctl_oom_dump_tasks) dump_tasks(oc);}
/* * Number of OOM victims in flight */static atomic_t oom_victims = ATOMIC_INIT(0);static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
static bool oom_killer_disabled __read_mostly;
/* * task->mm can be NULL if the task is the exited group leader. So to * determine whether the task is using a particular mm, we examine all the * task's threads: if one of those is using this mm then this task was also * using it. */bool process_shares_mm(const struct task_struct *p, const struct mm_struct *mm){ const struct task_struct *t;
for_each_thread(p, t) { const struct mm_struct *t_mm = READ_ONCE(t->mm); if (t_mm) return t_mm == mm; } return false;}
#ifdef CONFIG_MMU/* * OOM Reaper kernel thread which tries to reap the memory used by the OOM * victim (if that is possible) to help the OOM killer to move on. */static struct task_struct *oom_reaper_th;static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);static struct task_struct *oom_reaper_list;static DEFINE_SPINLOCK(oom_reaper_lock);
static bool __oom_reap_task_mm(struct mm_struct *mm){ struct vm_area_struct *vma; bool ret = true; MA_STATE(mas, &mm->mm_mt, ULONG_MAX, ULONG_MAX);
/* * Tell all users of get_user/copy_from_user etc... that the content * is no longer stable. No barriers really needed because unmapping * should imply barriers already and the reader would hit a page fault * if it stumbled over a reaped memory. */ mm_flags_set(MMF_UNSTABLE, mm);
/* * It might start racing with the dying task and compete for shared * resources - e.g. page table lock contention has been observed. * Reduce those races by reaping the oom victim from the other end * of the address space. */ mas_for_each_rev(&mas, vma, 0) { if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP)) continue;
/* * Only anonymous pages have a good chance to be dropped * without additional steps which we cannot afford as we * are OOM already. * * We do not even care about fs backed pages because all * which are reclaimable have already been reclaimed and * we do not want to block exit_mmap by keeping mm ref * count elevated without a good reason. */ if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) { if (zap_vma_for_reaping(vma)) ret = false; } }
return ret;}
/* * Reaps the address space of the given task. * * Returns true on success and false if none or part of the address space * has been reclaimed and the caller should retry later. */static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm){ bool ret = true;
if (!mmap_read_trylock(mm)) { trace_skip_task_reaping(tsk->pid); return false; }
/* * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't * work on the mm anymore. The check for MMF_OOM_SKIP must run * under mmap_lock for reading because it serializes against the * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap(). */ if (mm_flags_test(MMF_OOM_SKIP, mm)) { trace_skip_task_reaping(tsk->pid); goto out_unlock; }
trace_start_task_reaping(tsk->pid);
/* failed to reap part of the address space. Try again later */ ret = __oom_reap_task_mm(mm); if (!ret) goto out_finish;
pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", task_pid_nr(tsk), tsk->comm, K(get_mm_counter_sum(mm, MM_ANONPAGES)), K(get_mm_counter_sum(mm, MM_FILEPAGES)), K(get_mm_counter_sum(mm, MM_SHMEMPAGES)));out_finish: trace_finish_task_reaping(tsk->pid);out_unlock: mmap_read_unlock(mm);
return ret;}
#define MAX_OOM_REAP_RETRIES 10static void oom_reap_task(struct task_struct *tsk){ int attempts = 0; struct mm_struct *mm = tsk->signal->oom_mm;
/* Retry the mmap_read_trylock(mm) a few times */ while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm)) schedule_timeout_idle(HZ/10);
if (attempts <= MAX_OOM_REAP_RETRIES || mm_flags_test(MMF_OOM_SKIP, mm)) goto done;
pr_info("oom_reaper: unable to reap pid:%d (%s)\n", task_pid_nr(tsk), tsk->comm); sched_show_task(tsk); debug_show_all_locks();
done: tsk->oom_reaper_list = NULL;
/* * Hide this mm from OOM killer because it has been either reaped or * somebody can't call mmap_write_unlock(mm). */ mm_flags_set(MMF_OOM_SKIP, mm);
/* Drop a reference taken by queue_oom_reaper */ put_task_struct(tsk);}
static int oom_reaper(void *unused){ set_freezable();
while (true) { struct task_struct *tsk = NULL;
wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL); spin_lock_irq(&oom_reaper_lock); if (oom_reaper_list != NULL) { tsk = oom_reaper_list; oom_reaper_list = tsk->oom_reaper_list; } spin_unlock_irq(&oom_reaper_lock);
if (tsk) oom_reap_task(tsk); }
return 0;}
static void wake_oom_reaper(struct timer_list *timer){ struct task_struct *tsk = container_of(timer, struct task_struct, oom_reaper_timer); struct mm_struct *mm = tsk->signal->oom_mm; unsigned long flags;
/* The victim managed to terminate on its own - see exit_mmap */ if (mm_flags_test(MMF_OOM_SKIP, mm)) { put_task_struct(tsk); return; }
spin_lock_irqsave(&oom_reaper_lock, flags); tsk->oom_reaper_list = oom_reaper_list; oom_reaper_list = tsk; spin_unlock_irqrestore(&oom_reaper_lock, flags); trace_wake_reaper(tsk->pid); wake_up(&oom_reaper_wait);}
/* * Give the OOM victim time to exit naturally before invoking the oom_reaping. * The timers timeout is arbitrary... the longer it is, the longer the worst * case scenario for the OOM can take. If it is too small, the oom_reaper can * get in the way and release resources needed by the process exit path. * e.g. The futex robust list can sit in Anon|Private memory that gets reaped * before the exit path is able to wake the futex waiters. */#define OOM_REAPER_DELAY (2*HZ)static void queue_oom_reaper(struct task_struct *tsk){ /* mm is already queued? */ if (mm_flags_test_and_set(MMF_OOM_REAP_QUEUED, tsk->signal->oom_mm)) return;
get_task_struct(tsk); timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0); tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY; add_timer(&tsk->oom_reaper_timer);}
#ifdef CONFIG_SYSCTLstatic const struct ctl_table vm_oom_kill_table[] = { { .procname = "panic_on_oom", .data = &sysctl_panic_on_oom, .maxlen = sizeof(sysctl_panic_on_oom), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_TWO, }, { .procname = "oom_kill_allocating_task", .data = &sysctl_oom_kill_allocating_task, .maxlen = sizeof(sysctl_oom_kill_allocating_task), .mode = 0644, .proc_handler = proc_dointvec, }, { .procname = "oom_dump_tasks", .data = &sysctl_oom_dump_tasks, .maxlen = sizeof(sysctl_oom_dump_tasks), .mode = 0644, .proc_handler = proc_dointvec, },};#endif
static int __init oom_init(void){ oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");#ifdef CONFIG_SYSCTL register_sysctl_init("vm", vm_oom_kill_table);#endif return 0;}subsys_initcall(oom_init)#elsestatic inline void queue_oom_reaper(struct task_struct *tsk){}#endif /* CONFIG_MMU */
/** * mark_oom_victim - mark the given task as OOM victim * @tsk: task to mark * * Has to be called with oom_lock held and never after * oom has been disabled already. * * tsk->mm has to be non NULL and caller has to guarantee it is stable (either * under task_lock or operate on the current). */static void mark_oom_victim(struct task_struct *tsk){ const struct cred *cred; struct mm_struct *mm = tsk->mm;
WARN_ON(oom_killer_disabled); /* OOM killer might race with memcg OOM */ if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) return;
/* oom_mm is bound to the signal struct life time. */ if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) mmgrab(tsk->signal->oom_mm);
/* * Make sure that the process is woken up from uninterruptible sleep * if it is frozen because OOM killer wouldn't be able to free any * memory and livelock. The freezer will thaw the tasks that are OOM * victims regardless of the PM freezing and cgroup freezing states. */ thaw_process(tsk); atomic_inc(&oom_victims); cred = get_task_cred(tsk); trace_mark_victim(tsk, cred->uid.val); put_cred(cred);}
/** * exit_oom_victim - note the exit of an OOM victim */void exit_oom_victim(void){ clear_thread_flag(TIF_MEMDIE);
if (!atomic_dec_return(&oom_victims)) wake_up_all(&oom_victims_wait);}
/** * oom_killer_enable - enable OOM killer */void oom_killer_enable(void){ oom_killer_disabled = false; pr_info("OOM killer enabled.\n");}
/** * oom_killer_disable - disable OOM killer * @timeout: maximum timeout to wait for oom victims in jiffies * * Forces all page allocations to fail rather than trigger OOM killer. * Will block and wait until all OOM victims are killed or the given * timeout expires. * * The function cannot be called when there are runnable user tasks because * the userspace would see unexpected allocation failures as a result. Any * new usage of this function should be consulted with MM people. * * Returns true if successful and false if the OOM killer cannot be * disabled. */bool oom_killer_disable(signed long timeout){ signed long ret;
/* * Make sure to not race with an ongoing OOM killer. Check that the * current is not killed (possibly due to sharing the victim's memory). */ if (mutex_lock_killable(&oom_lock)) return false; oom_killer_disabled = true; mutex_unlock(&oom_lock);
ret = wait_event_interruptible_timeout(oom_victims_wait, !atomic_read(&oom_victims), timeout); if (ret <= 0) { oom_killer_enable(); return false; } pr_info("OOM killer disabled.\n");
return true;}
static inline bool __task_will_free_mem(struct task_struct *task){ struct signal_struct *sig = task->signal;
/* * A coredumping process may sleep for an extended period in * coredump_task_exit(), so the oom killer cannot assume that * the process will promptly exit and release memory. */ if (sig->core_state) return false;
if (sig->flags & SIGNAL_GROUP_EXIT) return true;
if (thread_group_empty(task) && (task->flags & PF_EXITING)) return true;
return false;}
/* * Checks whether the given task is dying or exiting and likely to * release its address space. This means that all threads and processes * sharing the same mm have to be killed or exiting. * Caller has to make sure that task->mm is stable (hold task_lock or * it operates on the current). */static bool task_will_free_mem(struct task_struct *task){ struct mm_struct *mm = task->mm; struct task_struct *p; bool ret = true;
/* * Skip tasks without mm because it might have passed its exit_mm and * exit_oom_victim. oom_reaper could have rescued that but do not rely * on that for now. We can consider find_lock_task_mm in future. */ if (!mm) return false;
if (!__task_will_free_mem(task)) return false;
/* * This task has already been drained by the oom reaper so there are * only small chances it will free some more */ if (mm_flags_test(MMF_OOM_SKIP, mm)) return false;
if (atomic_read(&mm->mm_users) <= 1) return true;
/* * Make sure that all tasks which share the mm with the given tasks * are dying as well to make sure that a) nobody pins its mm and * b) the task is also reapable by the oom reaper. */ rcu_read_lock(); for_each_process(p) { if (!process_shares_mm(p, mm)) continue; if (same_thread_group(task, p)) continue; ret = __task_will_free_mem(p); if (!ret) break; } rcu_read_unlock();
return ret;}
static void __oom_kill_process(struct task_struct *victim, const char *message){ struct task_struct *p; struct mm_struct *mm; bool can_oom_reap = true;
p = find_lock_task_mm(victim); if (!p) { pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n", message, task_pid_nr(victim), victim->comm); put_task_struct(victim); return; } else if (victim != p) { get_task_struct(p); put_task_struct(victim); victim = p; }
/* Get a reference to safely compare mm after task_unlock(victim) */ mm = victim->mm; mmgrab(mm);
/* Raise event before sending signal: task reaper must see this */ count_vm_event(OOM_KILL); memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
/* * We should send SIGKILL before granting access to memory reserves * in order to prevent the OOM victim from depleting the memory * reserves from the user space under its control. */ do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID); mark_oom_victim(victim); pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%d\n", message, task_pid_nr(victim), victim->comm, K(mm->total_vm), K(get_mm_counter_sum(mm, MM_ANONPAGES)), K(get_mm_counter_sum(mm, MM_FILEPAGES)), K(get_mm_counter_sum(mm, MM_SHMEMPAGES)), from_kuid(&init_user_ns, task_uid(victim)), mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj); task_unlock(victim);
/* * Kill all user processes sharing victim->mm in other thread groups, if * any. They don't get access to memory reserves, though, to avoid * depletion of all memory. This prevents mm->mmap_lock livelock when an * oom killed thread cannot exit because it requires the semaphore and * its contended by another thread trying to allocate memory itself. * That thread will now get access to memory reserves since it has a * pending fatal signal. */ rcu_read_lock(); for_each_process(p) { if (!process_shares_mm(p, mm)) continue; if (same_thread_group(p, victim)) continue; if (is_global_init(p)) { can_oom_reap = false; mm_flags_set(MMF_OOM_SKIP, mm); pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n", task_pid_nr(victim), victim->comm, task_pid_nr(p), p->comm); continue; } /* * No kthread_use_mm() user needs to read from the userspace so * we are ok to reap it. */ if (unlikely(p->flags & PF_KTHREAD)) continue; do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID); } rcu_read_unlock();
if (can_oom_reap) queue_oom_reaper(victim);
mmdrop(mm); put_task_struct(victim);}
/* * Kill provided task unless it's secured by setting * oom_score_adj to OOM_SCORE_ADJ_MIN. */static int oom_kill_memcg_member(struct task_struct *task, void *message){ if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN && !is_global_init(task)) { get_task_struct(task); __oom_kill_process(task, message); } return 0;}
static void oom_kill_process(struct oom_control *oc, const char *message){ struct task_struct *victim = oc->chosen; struct mem_cgroup *oom_group; static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
/* * If the task is already exiting, don't alarm the sysadmin or kill * its children or threads, just give it access to memory reserves * so it can die quickly */ task_lock(victim); if (task_will_free_mem(victim)) { mark_oom_victim(victim); queue_oom_reaper(victim); task_unlock(victim); put_task_struct(victim); return; } task_unlock(victim);
if (__ratelimit(&oom_rs)) { dump_header(oc); dump_oom_victim(oc, victim); }
/* * Do we need to kill the entire memory cgroup? * Or even one of the ancestor memory cgroups? * Check this out before killing the victim task. */ oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
__oom_kill_process(victim, message);
/* * If necessary, kill all tasks in the selected memory cgroup. */ if (oom_group) { memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL); mem_cgroup_print_oom_group(oom_group); mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member, (void *)message); mem_cgroup_put(oom_group); }}
/* * Determines whether the kernel must panic because of the panic_on_oom sysctl. */static void check_panic_on_oom(struct oom_control *oc){ if (likely(!sysctl_panic_on_oom)) return; if (sysctl_panic_on_oom != 2) { /* * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel * does not panic for cpuset, mempolicy, or memcg allocation * failures. */ if (oc->constraint != CONSTRAINT_NONE) return; } /* Do not panic for oom kills triggered by sysrq */ if (is_sysrq_oom(oc)) return; dump_header(oc); panic("Out of memory: %s panic_on_oom is enabled\n", sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");}
static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
int register_oom_notifier(struct notifier_block *nb){ return blocking_notifier_chain_register(&oom_notify_list, nb);}EXPORT_SYMBOL_GPL(register_oom_notifier);
int unregister_oom_notifier(struct notifier_block *nb){ return blocking_notifier_chain_unregister(&oom_notify_list, nb);}EXPORT_SYMBOL_GPL(unregister_oom_notifier);
/** * out_of_memory - kill the "best" process when we run out of memory * @oc: pointer to struct oom_control * * If we run out of memory, we have the choice between either * killing a random task (bad), letting the system crash (worse) * OR try to be smart about which process to kill. Note that we * don't have to be perfect here, we just have to be good. */bool out_of_memory(struct oom_control *oc){ unsigned long freed = 0;
if (oom_killer_disabled) return false;
if (!is_memcg_oom(oc)) { blocking_notifier_call_chain(&oom_notify_list, 0, &freed); if (freed > 0 && !is_sysrq_oom(oc)) /* Got some memory back in the last second. */ return true; }
/* * If current has a pending SIGKILL or is exiting, then automatically * select it. The goal is to allow it to allocate so that it may * quickly exit and free its memory. */ if (task_will_free_mem(current)) { mark_oom_victim(current); queue_oom_reaper(current); return true; }
/* * The OOM killer does not compensate for IO-less reclaim. * But mem_cgroup_oom() has to invoke the OOM killer even * if it is a GFP_NOFS allocation. */ if (!(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc)) return true;
/* * Check if there were limitations on the allocation (only relevant for * NUMA and memcg) that may require different handling. */ oc->constraint = constrained_alloc(oc); if (oc->constraint != CONSTRAINT_MEMORY_POLICY) oc->nodemask = NULL; check_panic_on_oom(oc);
if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task && current->mm && !oom_unkillable_task(current) && oom_cpuset_eligible(current, oc) && current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { get_task_struct(current); oc->chosen = current; oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)"); return true; }
select_bad_process(oc); /* Found nothing?!?! */ if (!oc->chosen) { dump_header(oc); pr_warn("Out of memory and no killable processes...\n"); /* * If we got here due to an actual allocation at the * system level, we cannot survive this and will enter * an endless loop in the allocator. Bail out now. */ if (!is_sysrq_oom(oc) && !is_memcg_oom(oc)) panic("System is deadlocked on memory\n"); } if (oc->chosen && oc->chosen != (void *)-1UL) oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" : "Memory cgroup out of memory"); return !!oc->chosen;}
/* * The pagefault handler calls here because some allocation has failed. We have * to take care of the memcg OOM here because this is the only safe context without * any locks held but let the oom killer triggered from the allocation context care * about the global OOM. */void pagefault_out_of_memory(void){ static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
if (mem_cgroup_oom_synchronize(true)) return;
if (fatal_signal_pending(current)) return;
if (__ratelimit(&pfoom_rs)) pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");}
SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags){#ifdef CONFIG_MMU struct mm_struct *mm = NULL; struct task_struct *task; struct task_struct *p; unsigned int f_flags; bool reap = false; long ret = 0;
if (flags) return -EINVAL;
task = pidfd_get_task(pidfd, &f_flags); if (IS_ERR(task)) return PTR_ERR(task);
/* * Make sure to choose a thread which still has a reference to mm * during the group exit */ p = find_lock_task_mm(task); if (!p) { ret = -ESRCH; goto put_task; }
mm = p->mm; mmgrab(mm);
if (task_will_free_mem(p)) reap = true; else { /* Error only if the work has not been done already */ if (!mm_flags_test(MMF_OOM_SKIP, mm)) ret = -EINVAL; } task_unlock(p);
if (!reap) goto drop_mm;
if (mmap_read_lock_killable(mm)) { ret = -EINTR; goto drop_mm; } /* * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure * possible change in exit_mmap is seen */ if (!mm_flags_test(MMF_OOM_SKIP, mm) && !__oom_reap_task_mm(mm)) ret = -EAGAIN; mmap_read_unlock(mm);
drop_mm: mmdrop(mm);put_task: put_task_struct(task); return ret;#else return -ENOSYS;#endif /* CONFIG_MMU */}