oom: remove unnecessary code and cleanup

[linux-2.6/libata-dev.git] / mm / oom_kill.c

/*
 *  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...
 *
 *  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/module.h>
#include <linux/notifier.h>
#include <linux/memcontrol.h>
#include <linux/mempolicy.h>
#include <linux/security.h>

int sysctl_panic_on_oom;
int sysctl_oom_kill_allocating_task;
int sysctl_oom_dump_tasks = 1;
static DEFINE_SPINLOCK(zone_scan_lock);
/* #define DEBUG */

#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;
                }
                tsk = next_thread(tsk);
        } while (tsk != start);
        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.
 */
static 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;
}

/**
 * badness - calculate a numeric value for how bad this task has been
 * @p: task struct of which task we should calculate
 * @uptime: current uptime in seconds
 *
 * The formula used is relatively simple and documented inline in the
 * function. The main rationale is that we want to select a good task
 * to kill when we run out of memory.
 *
 * Good in this context means that:
 * 1) we lose the minimum amount of work done
 * 2) we recover a large amount of memory
 * 3) we don't kill anything innocent of eating tons of memory
 * 4) we want to kill the minimum amount of processes (one)
 * 5) we try to kill the process the user expects us to kill, this
 *    algorithm has been meticulously tuned to meet the principle
 *    of least surprise ... (be careful when you change it)
 */

unsigned long badness(struct task_struct *p, unsigned long uptime)
{
        unsigned long points, cpu_time, run_time;
        struct task_struct *child;
        struct task_struct *c, *t;
        int oom_adj = p->signal->oom_adj;
        struct task_cputime task_time;
        unsigned long utime;
        unsigned long stime;

        if (oom_adj == OOM_DISABLE)
                return 0;

        p = find_lock_task_mm(p);
        if (!p)
                return 0;

        /*
         * The memory size of the process is the basis for the badness.
         */
        points = p->mm->total_vm;
        task_unlock(p);

        /*
         * swapoff can easily use up all memory, so kill those first.
         */
        if (p->flags & PF_OOM_ORIGIN)
                return ULONG_MAX;

        /*
         * Processes which fork a lot of child processes are likely
         * a good choice. We add half the vmsize of the children if they
         * have an own mm. This prevents forking servers to flood the
         * machine with an endless amount of children. In case a single
         * child is eating the vast majority of memory, adding only half
         * to the parents will make the child our kill candidate of choice.
         */
        t = p;
        do {
                list_for_each_entry(c, &t->children, sibling) {
                        child = find_lock_task_mm(c);
                        if (child) {
                                if (child->mm != p->mm)
                                        points += child->mm->total_vm/2 + 1;
                                task_unlock(child);
                        }
                }
        } while_each_thread(p, t);

        /*
         * CPU time is in tens of seconds and run time is in thousands
         * of seconds. There is no particular reason for this other than
         * that it turned out to work very well in practice.
         */
        thread_group_cputime(p, &task_time);
        utime = cputime_to_jiffies(task_time.utime);
        stime = cputime_to_jiffies(task_time.stime);
        cpu_time = (utime + stime) >> (SHIFT_HZ + 3);


        if (uptime >= p->start_time.tv_sec)
                run_time = (uptime - p->start_time.tv_sec) >> 10;
        else
                run_time = 0;

        if (cpu_time)
                points /= int_sqrt(cpu_time);
        if (run_time)
                points /= int_sqrt(int_sqrt(run_time));

        /*
         * Niced processes are most likely less important, so double
         * their badness points.
         */
        if (task_nice(p) > 0)
                points *= 2;

        /*
         * Superuser processes are usually more important, so we make it
         * less likely that we kill those.
         */
        if (has_capability_noaudit(p, CAP_SYS_ADMIN) ||
            has_capability_noaudit(p, CAP_SYS_RESOURCE))
                points /= 4;

        /*
         * We don't want to kill a process with direct hardware access.
         * Not only could that mess up the hardware, but usually users
         * tend to only have this flag set on applications they think
         * of as important.
         */
        if (has_capability_noaudit(p, CAP_SYS_RAWIO))
                points /= 4;

        /*
         * Adjust the score by oom_adj.
         */
        if (oom_adj) {
                if (oom_adj > 0) {
                        if (!points)
                                points = 1;
                        points <<= oom_adj;
                } else
                        points >>= -(oom_adj);
        }

#ifdef DEBUG
        printk(KERN_DEBUG "OOMkill: task %d (%s) got %lu points\n",
        p->pid, p->comm, points);
#endif
        return points;
}

/*
 * 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)
{
        struct zone *zone;
        struct zoneref *z;
        enum zone_type high_zoneidx = gfp_zone(gfp_mask);

        /*
         * 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;

        /*
         * The nodemask here is a nodemask passed to alloc_pages(). Now,
         * cpuset doesn't use this nodemask for its hardwall/softwall/hierarchy
         * feature. mempolicy is an only user of nodemask here.
         * check mempolicy's nodemask contains all N_HIGH_MEMORY
         */
        if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask))
                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))
                        return CONSTRAINT_CPUSET;

        return CONSTRAINT_NONE;
}
#else
static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
                                gfp_t gfp_mask, nodemask_t *nodemask)
{
        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 long *ppoints,
                struct mem_cgroup *mem, enum oom_constraint constraint,
                const nodemask_t *mask)
{
        struct task_struct *p;
        struct task_struct *chosen = NULL;
        struct timespec uptime;
        *ppoints = 0;

        do_posix_clock_monotonic_gettime(&uptime);
        for_each_process(p) {
                unsigned long points;

                /* skip the init task and kthreads */
                if (is_global_init(p) || (p->flags & PF_KTHREAD))
                        continue;
                if (mem && !task_in_mem_cgroup(p, mem))
                        continue;
                if (!has_intersects_mems_allowed(p,
                                constraint == CONSTRAINT_MEMORY_POLICY ? mask :
                                                                         NULL))
                        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))
                        return ERR_PTR(-1UL);

                /*
                 * This is in the process of releasing memory so wait for it
                 * to finish before killing some other task by mistake.
                 *
                 * However, if p is the current task, we allow the 'kill' to
                 * go ahead if it is exiting: this will simply set TIF_MEMDIE,
                 * which will allow it to gain access to memory reserves in
                 * the process of exiting and releasing its resources.
                 * Otherwise we could get an easy OOM deadlock.
                 */
                if ((p->flags & PF_EXITING) && p->mm) {
                        if (p != current)
                                return ERR_PTR(-1UL);

                        chosen = p;
                        *ppoints = ULONG_MAX;
                }

                if (p->signal->oom_adj == OOM_DISABLE)
                        continue;

                points = badness(p, uptime.tv_sec);
                if (points > *ppoints || !chosen) {
                        chosen = p;
                        *ppoints = points;
                }
        }

        return chosen;
}

/**
 * dump_tasks - dump current memory state of all system tasks
 * @mem: current's memory controller, if constrained
 *
 * Dumps the current memory state of all system tasks, excluding kernel threads.
 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
 * score, and name.
 *
 * If the actual is non-NULL, only tasks that are a member of the mem_cgroup are
 * shown.
 *
 * Call with tasklist_lock read-locked.
 */
static void dump_tasks(const struct mem_cgroup *mem)
{
        struct task_struct *p;
        struct task_struct *task;

        printk(KERN_INFO "[ pid ]   uid  tgid total_vm      rss cpu oom_adj "
               "name\n");
        for_each_process(p) {
                if (p->flags & PF_KTHREAD)
                        continue;
                if (mem && !task_in_mem_cgroup(p, mem))
                        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;
                }

                printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3u     %3d %s\n",
                       task->pid, __task_cred(task)->uid, task->tgid,
                       task->mm->total_vm, get_mm_rss(task->mm),
                       task_cpu(task), task->signal->oom_adj, task->comm);
                task_unlock(task);
        }
}

static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
                                                        struct mem_cgroup *mem)
{
        task_lock(current);
        pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
                "oom_adj=%d\n",
                current->comm, gfp_mask, order, current->signal->oom_adj);
        cpuset_print_task_mems_allowed(current);
        task_unlock(current);
        dump_stack();
        mem_cgroup_print_oom_info(mem, p);
        show_mem();
        if (sysctl_oom_dump_tasks)
                dump_tasks(mem);
}

#define K(x) ((x) << (PAGE_SHIFT-10))
static int oom_kill_task(struct task_struct *p)
{
        p = find_lock_task_mm(p);
        if (!p || p->signal->oom_adj == OOM_DISABLE) {
                task_unlock(p);
                return 1;
        }
        pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
                task_pid_nr(p), p->comm, K(p->mm->total_vm),
                K(get_mm_counter(p->mm, MM_ANONPAGES)),
                K(get_mm_counter(p->mm, MM_FILEPAGES)));
        task_unlock(p);

        p->rt.time_slice = HZ;
        set_tsk_thread_flag(p, TIF_MEMDIE);
        force_sig(SIGKILL, p);
        return 0;
}
#undef K

static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
                            unsigned long points, struct mem_cgroup *mem,
                            const char *message)
{
        struct task_struct *victim = p;
        struct task_struct *child;
        struct task_struct *t = p;
        unsigned long victim_points = 0;
        struct timespec uptime;

        if (printk_ratelimit())
                dump_header(p, gfp_mask, order, mem);

        /*
         * 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 0;
        }

        task_lock(p);
        pr_err("%s: Kill process %d (%s) score %lu 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 badness() score is sacrificed for its
         * parent.  This attempts to lose the minimal amount of work done while
         * still freeing memory.
         */
        do_posix_clock_monotonic_gettime(&uptime);
        do {
                list_for_each_entry(child, &t->children, sibling) {
                        unsigned long child_points;

                        if (child->mm == p->mm)
                                continue;
                        if (mem && !task_in_mem_cgroup(child, mem))
                                continue;

                        /* badness() returns 0 if the thread is unkillable */
                        child_points = badness(child, uptime.tv_sec);
                        if (child_points > victim_points) {
                                victim = child;
                                victim_points = child_points;
                        }
                }
        } while_each_thread(p, t);

        return oom_kill_task(victim);
}

/*
 * 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)
{
        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 (constraint != CONSTRAINT_NONE)
                        return;
        }
        read_lock(&tasklist_lock);
        dump_header(NULL, gfp_mask, order, NULL);
        read_unlock(&tasklist_lock);
        panic("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 *mem, gfp_t gfp_mask)
{
        unsigned long points = 0;
        struct task_struct *p;

        check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0);
        read_lock(&tasklist_lock);
retry:
        p = select_bad_process(&points, mem, CONSTRAINT_MEMCG, NULL);
        if (!p || PTR_ERR(p) == -1UL)
                goto out;

        if (oom_kill_process(p, gfp_mask, 0, points, mem,
                                "Memory cgroup out of memory"))
                goto retry;
out:
        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_zone_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_zone_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);
}


/*
 * Must be called with tasklist_lock held for read.
 */
static void __out_of_memory(gfp_t gfp_mask, int order,
                        enum oom_constraint constraint, const nodemask_t *mask)
{
        struct task_struct *p;
        unsigned long points;

        if (sysctl_oom_kill_allocating_task)
                if (!oom_kill_process(current, gfp_mask, order, 0, NULL,
                                "Out of memory (oom_kill_allocating_task)"))
                        return;
retry:
        /*
         * Rambo mode: Shoot down a process and hope it solves whatever
         * issues we may have.
         */
        p = select_bad_process(&points, NULL, constraint, mask);

        if (PTR_ERR(p) == -1UL)
                return;

        /* Found nothing?!?! Either we hang forever, or we panic. */
        if (!p) {
                dump_header(NULL, gfp_mask, order, NULL);
                read_unlock(&tasklist_lock);
                panic("Out of memory and no killable processes...\n");
        }

        if (oom_kill_process(p, gfp_mask, order, points, NULL,
                             "Out of memory"))
                goto retry;
}

/**
 * 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
 *
 * 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)
{
        unsigned long freed = 0;
        enum oom_constraint constraint = CONSTRAINT_NONE;

        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.
         */
        if (zonelist)
                constraint = constrained_alloc(zonelist, gfp_mask, nodemask);
        check_panic_on_oom(constraint, gfp_mask, order);
        read_lock(&tasklist_lock);
        __out_of_memory(gfp_mask, order, constraint, nodemask);
        read_unlock(&tasklist_lock);

        /*
         * Give "p" a good chance of killing itself before we
         * retry to allocate memory unless "p" is current
         */
        if (!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);
                clear_system_oom();
        }
        if (!test_thread_flag(TIF_MEMDIE))
                schedule_timeout_uninterruptible(1);
}