[T106][ZXW-22]7520V3SCV2.01.01.02P42U09_VEC_V0.8_AP_VEC origin source commit
Change-Id: Ic6e05d89ecd62fc34f82b23dcf306c93764aec4b
diff --git a/ap/os/linux/linux-3.4.x/mm/oom_kill.c b/ap/os/linux/linux-3.4.x/mm/oom_kill.c
new file mode 100644
index 0000000..b72c880
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/mm/oom_kill.c
@@ -0,0 +1,801 @@
+/*
+ * linux/mm/oom_kill.c
+ *
+ * Copyright (C) 1998,2000 Rik van Riel
+ * Thanks go out to Claus Fischer for some serious inspiration and
+ * for goading me into coding this file...
+ * Copyright (C) 2010 Google, Inc.
+ * Rewritten by David Rientjes
+ *
+ * The routines in this file are used to kill a process when
+ * we're seriously out of memory. This gets called from __alloc_pages()
+ * in mm/page_alloc.c when we really run out of memory.
+ *
+ * Since we won't call these routines often (on a well-configured
+ * machine) this file will double as a 'coding guide' and a signpost
+ * for newbie kernel hackers. It features several pointers to major
+ * kernel subsystems and hints as to where to find out what things do.
+ */
+
+#include <linux/oom.h>
+#include <linux/mm.h>
+#include <linux/err.h>
+#include <linux/gfp.h>
+#include <linux/sched.h>
+#include <linux/swap.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>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/oom.h>
+
+int sysctl_panic_on_oom;
+int sysctl_oom_kill_allocating_task;
+int sysctl_oom_dump_tasks = 1;
+static DEFINE_SPINLOCK(zone_scan_lock);
+
+/*
+ * compare_swap_oom_score_adj() - compare and swap current's oom_score_adj
+ * @old_val: old oom_score_adj for compare
+ * @new_val: new oom_score_adj for swap
+ *
+ * Sets the oom_score_adj value for current to @new_val iff its present value is
+ * @old_val. Usually used to reinstate a previous value to prevent racing with
+ * userspacing tuning the value in the interim.
+ */
+void compare_swap_oom_score_adj(int old_val, int new_val)
+{
+ struct sighand_struct *sighand = current->sighand;
+
+ spin_lock_irq(&sighand->siglock);
+ if (current->signal->oom_score_adj == old_val)
+ current->signal->oom_score_adj = new_val;
+ trace_oom_score_adj_update(current);
+ spin_unlock_irq(&sighand->siglock);
+}
+
+/**
+ * test_set_oom_score_adj() - set current's oom_score_adj and return old value
+ * @new_val: new oom_score_adj value
+ *
+ * Sets the oom_score_adj value for current to @new_val with proper
+ * synchronization and returns the old value. Usually used to temporarily
+ * set a value, save the old value in the caller, and then reinstate it later.
+ */
+int test_set_oom_score_adj(int new_val)
+{
+ struct sighand_struct *sighand = current->sighand;
+ int old_val;
+
+ spin_lock_irq(&sighand->siglock);
+ old_val = current->signal->oom_score_adj;
+ current->signal->oom_score_adj = new_val;
+ trace_oom_score_adj_update(current);
+ spin_unlock_irq(&sighand->siglock);
+
+ return old_val;
+}
+
+#ifdef CONFIG_NUMA
+/**
+ * has_intersects_mems_allowed() - check task eligiblity for kill
+ * @tsk: task struct of which task to consider
+ * @mask: nodemask passed to page allocator for mempolicy ooms
+ *
+ * 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.
+ */
+static bool has_intersects_mems_allowed(struct task_struct *tsk,
+ const nodemask_t *mask)
+{
+ struct task_struct *start = tsk;
+
+ do {
+ 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.
+ */
+ if (mempolicy_nodemask_intersects(tsk, mask))
+ return true;
+ } else {
+ /*
+ * This is not a mempolicy constrained oom, so only
+ * check the mems of tsk's cpuset.
+ */
+ if (cpuset_mems_allowed_intersects(current, tsk))
+ return true;
+ }
+ } while_each_thread(start, tsk);
+
+ return false;
+}
+#else
+static bool has_intersects_mems_allowed(struct task_struct *tsk,
+ const nodemask_t *mask)
+{
+ return true;
+}
+#endif /* CONFIG_NUMA */
+
+/*
+ * The process p may have detached its own ->mm while exiting or through
+ * 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 = p;
+
+ do {
+ task_lock(t);
+ if (likely(t->mm))
+ return t;
+ task_unlock(t);
+ } while_each_thread(p, t);
+
+ return NULL;
+}
+
+/* return true if the task is not adequate as candidate victim task. */
+static bool oom_unkillable_task(struct task_struct *p,
+ const struct mem_cgroup *memcg, const nodemask_t *nodemask)
+{
+ if (is_global_init(p))
+ return true;
+ if (p->flags & PF_KTHREAD)
+ return true;
+
+ /* When mem_cgroup_out_of_memory() and p is not member of the group */
+ if (memcg && !task_in_mem_cgroup(p, memcg))
+ return true;
+
+ /* p may not have freeable memory in nodemask */
+ if (!has_intersects_mems_allowed(p, nodemask))
+ return true;
+
+ return false;
+}
+
+/**
+ * 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.
+ */
+unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
+ const nodemask_t *nodemask, unsigned long totalpages)
+{
+ long points;
+
+ if (oom_unkillable_task(p, memcg, nodemask))
+ return 0;
+
+ p = find_lock_task_mm(p);
+ if (!p)
+ return 0;
+
+ if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
+ task_unlock(p);
+ return 0;
+ }
+
+ /*
+ * The memory controller may have a limit of 0 bytes, so avoid a divide
+ * by zero, if necessary.
+ */
+ if (!totalpages)
+ totalpages = 1;
+
+ /*
+ * 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(p->mm) + p->mm->nr_ptes;
+ points += get_mm_counter(p->mm, MM_SWAPENTS);
+
+ points *= 1000;
+ points /= totalpages;
+ task_unlock(p);
+
+ /*
+ * Root processes get 3% bonus, just like the __vm_enough_memory()
+ * implementation used by LSMs.
+ */
+ if (has_capability_noaudit(p, CAP_SYS_ADMIN))
+ points -= 30;
+
+ /*
+ * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
+ * either completely disable oom killing or always prefer a certain
+ * task.
+ */
+ points += p->signal->oom_score_adj;
+
+ /*
+ * Never return 0 for an eligible task that may be killed since it's
+ * possible that no single user task uses more than 0.1% of memory and
+ * no single admin tasks uses more than 3.0%.
+ */
+ if (points <= 0)
+ return 1;
+ return (points < 1000) ? points : 1000;
+}
+
+/*
+ * Determine the type of allocation constraint.
+ */
+#ifdef CONFIG_NUMA
+static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
+ gfp_t gfp_mask, nodemask_t *nodemask,
+ unsigned long *totalpages)
+{
+ struct zone *zone;
+ struct zoneref *z;
+ enum zone_type high_zoneidx = gfp_zone(gfp_mask);
+ bool cpuset_limited = false;
+ int nid;
+
+ /* Default to all available memory */
+ *totalpages = totalram_pages + total_swap_pages;
+
+ if (!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 (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 (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
+ *totalpages = total_swap_pages;
+ for_each_node_mask(nid, *nodemask)
+ *totalpages += node_spanned_pages(nid);
+ return CONSTRAINT_MEMORY_POLICY;
+ }
+
+ /* Check this allocation failure is caused by cpuset's wall function */
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ high_zoneidx, nodemask)
+ if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
+ cpuset_limited = true;
+
+ if (cpuset_limited) {
+ *totalpages = total_swap_pages;
+ for_each_node_mask(nid, cpuset_current_mems_allowed)
+ *totalpages += node_spanned_pages(nid);
+ return CONSTRAINT_CPUSET;
+ }
+ return CONSTRAINT_NONE;
+}
+#else
+static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
+ gfp_t gfp_mask, nodemask_t *nodemask,
+ unsigned long *totalpages)
+{
+ *totalpages = totalram_pages + total_swap_pages;
+ return CONSTRAINT_NONE;
+}
+#endif
+
+/*
+ * Simple selection loop. We chose the process with the highest
+ * number of 'points'. We expect the caller will lock the tasklist.
+ *
+ * (not docbooked, we don't want this one cluttering up the manual)
+ */
+static struct task_struct *select_bad_process(unsigned int *ppoints,
+ unsigned long totalpages, struct mem_cgroup *memcg,
+ const nodemask_t *nodemask, bool force_kill)
+{
+ struct task_struct *g, *p;
+ struct task_struct *chosen = NULL;
+ *ppoints = 0;
+
+ do_each_thread(g, p) {
+ unsigned int points;
+
+ if (p->exit_state)
+ continue;
+ if (oom_unkillable_task(p, memcg, nodemask))
+ continue;
+
+ /*
+ * This task already has access to memory reserves and is
+ * being killed. Don't allow any other task access to the
+ * memory reserve.
+ *
+ * Note: this may have a chance of deadlock if it gets
+ * blocked waiting for another task which itself is waiting
+ * for memory. Is there a better alternative?
+ */
+ if (test_tsk_thread_flag(p, TIF_MEMDIE)) {
+ if (unlikely(frozen(p)))
+ __thaw_task(p);
+ if (!force_kill)
+ return ERR_PTR(-1UL);
+ }
+ if (!p->mm)
+ continue;
+
+ if (p->flags & PF_EXITING) {
+ /*
+ * If p is the current task and is in the process of
+ * releasing memory, we allow the "kill" to set
+ * TIF_MEMDIE, which will allow it to gain access to
+ * memory reserves. Otherwise, it may stall forever.
+ *
+ * The loop isn't broken here, however, in case other
+ * threads are found to have already been oom killed.
+ */
+ if (p == current) {
+ chosen = p;
+ *ppoints = 1000;
+ } else if (!force_kill) {
+ /*
+ * If this task is not being ptraced on exit,
+ * then wait for it to finish before killing
+ * some other task unnecessarily.
+ */
+ if (!(p->group_leader->ptrace & PT_TRACE_EXIT))
+ return ERR_PTR(-1UL);
+ }
+ }
+
+ points = oom_badness(p, memcg, nodemask, totalpages);
+ if (points > *ppoints) {
+ chosen = p;
+ *ppoints = points;
+ }
+ } while_each_thread(g, p);
+
+ return chosen;
+}
+
+/**
+ * dump_tasks - dump current memory state of all system tasks
+ * @mem: current's memory controller, if constrained
+ * @nodemask: nodemask passed to page allocator for mempolicy ooms
+ *
+ * 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, cpu, oom_adj
+ * value, oom_score_adj value, and name.
+ *
+ * Call with tasklist_lock read-locked.
+ */
+static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemask)
+{
+ struct task_struct *p;
+ struct task_struct *task;
+
+ pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
+ for_each_process(p) {
+ if (oom_unkillable_task(p, memcg, nodemask))
+ continue;
+
+ task = find_lock_task_mm(p);
+ if (!task) {
+ /*
+ * This is a kthread or 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.
+ */
+ continue;
+ }
+
+ pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
+ task->pid, task_uid(task), task->tgid,
+ task->mm->total_vm, get_mm_rss(task->mm),
+ task_cpu(task), task->signal->oom_adj,
+ task->signal->oom_score_adj, task->comm);
+ task_unlock(task);
+ }
+}
+
+static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
+ struct mem_cgroup *memcg, const nodemask_t *nodemask)
+{
+ task_lock(current);
+ pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
+ "oom_adj=%d, oom_score_adj=%d\n",
+ current->comm, gfp_mask, order, current->signal->oom_adj,
+ current->signal->oom_score_adj);
+ cpuset_print_task_mems_allowed(current);
+ task_unlock(current);
+ dump_stack();
+ mem_cgroup_print_oom_info(memcg, p);
+ show_mem(SHOW_MEM_FILTER_NODES);
+ if (sysctl_oom_dump_tasks)
+ dump_tasks(memcg, nodemask);
+}
+
+/*
+ * Number of OOM killer invocations (including memcg OOM killer).
+ * Primarily used by PM freezer to check for potential races with
+ * OOM killed frozen task.
+ */
+static atomic_t oom_kills = ATOMIC_INIT(0);
+
+int oom_kills_count(void)
+{
+ return atomic_read(&oom_kills);
+}
+
+void note_oom_kill(void)
+{
+ atomic_inc(&oom_kills);
+}
+
+#define K(x) ((x) << (PAGE_SHIFT-10))
+static void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
+ unsigned int points, unsigned long totalpages,
+ struct mem_cgroup *memcg, nodemask_t *nodemask,
+ const char *message)
+{
+ struct task_struct *victim = p;
+ struct task_struct *child;
+ struct task_struct *t = p;
+ struct mm_struct *mm;
+ unsigned int victim_points = 0;
+ 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 set TIF_MEMDIE so it can die quickly
+ */
+ if (p->flags & PF_EXITING) {
+ set_tsk_thread_flag(p, TIF_MEMDIE);
+ return;
+ }
+
+ if (__ratelimit(&oom_rs))
+ dump_header(p, gfp_mask, order, memcg, nodemask);
+
+ task_lock(p);
+ pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
+ message, task_pid_nr(p), p->comm, points);
+ task_unlock(p);
+
+ /*
+ * If any of p's children has a different mm and is eligible for kill,
+ * the one with the highest oom_badness() score is sacrificed for its
+ * parent. This attempts to lose the minimal amount of work done while
+ * still freeing memory.
+ */
+ do {
+ list_for_each_entry(child, &t->children, sibling) {
+ unsigned int child_points;
+
+ if (child->mm == p->mm)
+ continue;
+ /*
+ * oom_badness() returns 0 if the thread is unkillable
+ */
+ child_points = oom_badness(child, memcg, nodemask,
+ totalpages);
+ if (child_points > victim_points) {
+ victim = child;
+ victim_points = child_points;
+ }
+ }
+ } while_each_thread(p, t);
+
+ victim = find_lock_task_mm(victim);
+ if (!victim)
+ return;
+
+ /* mm cannot safely be dereferenced after task_unlock(victim) */
+ mm = victim->mm;
+ pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
+ task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
+ K(get_mm_counter(victim->mm, MM_ANONPAGES)),
+ K(get_mm_counter(victim->mm, MM_FILEPAGES)));
+ 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_sem 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.
+ */
+ for_each_process(p)
+ if (p->mm == mm && !same_thread_group(p, victim) &&
+ !(p->flags & PF_KTHREAD)) {
+ if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
+ continue;
+
+ task_lock(p); /* Protect ->comm from prctl() */
+ pr_err("Kill process %d (%s) sharing same memory\n",
+ task_pid_nr(p), p->comm);
+ task_unlock(p);
+ do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
+ }
+
+ set_tsk_thread_flag(victim, TIF_MEMDIE);
+ do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
+}
+#undef K
+
+/*
+ * Determines whether the kernel must panic because of the panic_on_oom sysctl.
+ */
+static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
+ int order, const nodemask_t *nodemask)
+{
+ if (likely(!sysctl_panic_on_oom))
+ return;
+
+ sysctl_panic_on_oom = 2;
+ 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 (constraint != CONSTRAINT_NONE)
+ return;
+ }
+ read_lock(&tasklist_lock);
+ dump_header(NULL, gfp_mask, order, NULL, nodemask);
+ read_unlock(&tasklist_lock);
+ panic("[zx297510]Out of memory: %s panic_on_oom is enabled\n",
+ sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
+}
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
+ int order)
+{
+ unsigned long limit;
+ unsigned int points = 0;
+ struct task_struct *p;
+
+ /*
+ * 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 (fatal_signal_pending(current) || current->flags & PF_EXITING) {
+ set_thread_flag(TIF_MEMDIE);
+ return;
+ }
+
+ check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, order, NULL);
+ limit = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT;
+ read_lock(&tasklist_lock);
+ p = select_bad_process(&points, limit, memcg, NULL, false);
+ if (p && PTR_ERR(p) != -1UL)
+ oom_kill_process(p, gfp_mask, order, points, limit, memcg, NULL,
+ "Memory cgroup out of memory");
+ read_unlock(&tasklist_lock);
+}
+#endif
+
+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);
+
+/*
+ * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
+ * if a parallel OOM killing is already taking place that includes a zone in
+ * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
+ */
+int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+{
+ struct zoneref *z;
+ struct zone *zone;
+ int ret = 1;
+
+ spin_lock(&zone_scan_lock);
+ for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+ if (zone_is_oom_locked(zone)) {
+ ret = 0;
+ goto out;
+ }
+ }
+
+ for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+ /*
+ * Lock each zone in the zonelist under zone_scan_lock so a
+ * parallel invocation of try_set_zonelist_oom() doesn't succeed
+ * when it shouldn't.
+ */
+ zone_set_flag(zone, ZONE_OOM_LOCKED);
+ }
+
+out:
+ spin_unlock(&zone_scan_lock);
+ return ret;
+}
+
+/*
+ * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
+ * allocation attempts with zonelists containing them may now recall the OOM
+ * killer, if necessary.
+ */
+void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+{
+ struct zoneref *z;
+ struct zone *zone;
+
+ spin_lock(&zone_scan_lock);
+ for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+ zone_clear_flag(zone, ZONE_OOM_LOCKED);
+ }
+ spin_unlock(&zone_scan_lock);
+}
+
+/*
+ * Try to acquire the oom killer lock for all system zones. Returns zero if a
+ * parallel oom killing is taking place, otherwise locks all zones and returns
+ * non-zero.
+ */
+static int try_set_system_oom(void)
+{
+ struct zone *zone;
+ int ret = 1;
+
+ spin_lock(&zone_scan_lock);
+ for_each_populated_zone(zone)
+ if (zone_is_oom_locked(zone)) {
+ ret = 0;
+ goto out;
+ }
+ for_each_populated_zone(zone)
+ zone_set_flag(zone, ZONE_OOM_LOCKED);
+out:
+ spin_unlock(&zone_scan_lock);
+ return ret;
+}
+
+/*
+ * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
+ * attempts or page faults may now recall the oom killer, if necessary.
+ */
+static void clear_system_oom(void)
+{
+ struct zone *zone;
+
+ spin_lock(&zone_scan_lock);
+ for_each_populated_zone(zone)
+ zone_clear_flag(zone, ZONE_OOM_LOCKED);
+ spin_unlock(&zone_scan_lock);
+}
+
+/**
+ * out_of_memory - kill the "best" process when we run out of memory
+ * @zonelist: zonelist pointer
+ * @gfp_mask: memory allocation flags
+ * @order: amount of memory being requested as a power of 2
+ * @nodemask: nodemask passed to page allocator
+ * @force_kill: true if a task must be killed, even if others are exiting
+ *
+ * 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.
+ */
+void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
+ int order, nodemask_t *nodemask, bool force_kill)
+{
+ const nodemask_t *mpol_mask;
+ struct task_struct *p;
+ unsigned long totalpages;
+ unsigned long freed = 0;
+ unsigned int points;
+ enum oom_constraint constraint = CONSTRAINT_NONE;
+ int killed = 0;
+
+ blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
+ if (freed > 0)
+ /* Got some memory back in the last second. */
+ return;
+
+ /*
+ * If current has a pending SIGKILL, then automatically select it. The
+ * goal is to allow it to allocate so that it may quickly exit and free
+ * its memory.
+ */
+ if (fatal_signal_pending(current)) {
+ set_thread_flag(TIF_MEMDIE);
+ return;
+ }
+
+ /*
+ * Check if there were limitations on the allocation (only relevant for
+ * NUMA) that may require different handling.
+ */
+ constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
+ &totalpages);
+ mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
+ check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
+
+ read_lock(&tasklist_lock);
+ if (sysctl_oom_kill_allocating_task &&
+ !oom_unkillable_task(current, NULL, nodemask) &&
+ current->mm) {
+ oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
+ nodemask,
+ "Out of memory (oom_kill_allocating_task)");
+ goto out;
+ }
+
+ p = select_bad_process(&points, totalpages, NULL, mpol_mask,
+ force_kill);
+ /* Found nothing?!?! Either we hang forever, or we panic. */
+ if (!p) {
+ dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
+ read_unlock(&tasklist_lock);
+ panic("Out of memory and no killable processes...\n");
+ }
+ if (PTR_ERR(p) != -1UL) {
+ oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
+ nodemask, "Out of memory");
+ killed = 1;
+ }
+out:
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Give "p" a good chance of killing itself before we
+ * retry to allocate memory unless "p" is current
+ */
+ if (killed && !test_thread_flag(TIF_MEMDIE))
+ schedule_timeout_uninterruptible(1);
+}
+
+/*
+ * The pagefault handler calls here because it is out of memory, so kill a
+ * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
+ * oom killing is already in progress so do nothing. If a task is found with
+ * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
+ */
+void pagefault_out_of_memory(void)
+{
+ if (try_set_system_oom()) {
+ out_of_memory(NULL, 0, 0, NULL, false);
+ clear_system_oom();
+ }
+ if (!test_thread_flag(TIF_MEMDIE))
+ schedule_timeout_uninterruptible(1);
+}