[PATCH] EDAC: cleanup code for clearing initial errors

[linux-2.6] / 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/mm.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/cpuset.h>

/* #define DEBUG */

/**
 * oom_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, s;
        struct list_head *tsk;

        if (!p->mm)
                return 0;

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

        /*
         * 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.
         */
        list_for_each(tsk, &p->children) {
                struct task_struct *chld;
                chld = list_entry(tsk, struct task_struct, sibling);
                if (chld->mm != p->mm && chld->mm)
                        points += chld->mm->total_vm/2 + 1;
        }

        /*
         * 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.
         */
        cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime))
                >> (SHIFT_HZ + 3);

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

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

        /*
         * 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 (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) ||
                                p->uid == 0 || p->euid == 0)
                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 (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO))
                points /= 4;

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

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

/*
 * Types of limitations to the nodes from which allocations may occur
 */
#define CONSTRAINT_NONE 1
#define CONSTRAINT_MEMORY_POLICY 2
#define CONSTRAINT_CPUSET 3

/*
 * Determine the type of allocation constraint.
 */
static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
{
#ifdef CONFIG_NUMA
        struct zone **z;
        nodemask_t nodes = node_online_map;

        for (z = zonelist->zones; *z; z++)
                if (cpuset_zone_allowed(*z, gfp_mask))
                        node_clear((*z)->zone_pgdat->node_id,
                                        nodes);
                else
                        return CONSTRAINT_CPUSET;

        if (!nodes_empty(nodes))
                return CONSTRAINT_MEMORY_POLICY;
#endif

        return CONSTRAINT_NONE;
}

/*
 * 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 task_struct *g, *p;
        struct task_struct *chosen = NULL;
        struct timespec uptime;
        *ppoints = 0;

        do_posix_clock_monotonic_gettime(&uptime);
        do_each_thread(g, p) {
                unsigned long points;
                int releasing;

                /* skip the init task with pid == 1 */
                if (p->pid == 1)
                        continue;
                if (p->oomkilladj == OOM_DISABLE)
                        continue;
                /* If p's nodes don't overlap ours, it won't help to kill p. */
                if (!cpuset_excl_nodes_overlap(p))
                        continue;

                /*
                 * This is in the process of releasing memory so for wait it
                 * to finish before killing some other task by mistake.
                 */
                releasing = test_tsk_thread_flag(p, TIF_MEMDIE) ||
                                                p->flags & PF_EXITING;
                if (releasing && !(p->flags & PF_DEAD))
                        return ERR_PTR(-1UL);
                if (p->flags & PF_SWAPOFF)
                        return p;

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

/**
 * We must be careful though to never send SIGKILL a process with
 * CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that
 * we select a process with CAP_SYS_RAW_IO set).
 */
static void __oom_kill_task(task_t *p, const char *message)
{
        if (p->pid == 1) {
                WARN_ON(1);
                printk(KERN_WARNING "tried to kill init!\n");
                return;
        }

        task_lock(p);
        if (!p->mm || p->mm == &init_mm) {
                WARN_ON(1);
                printk(KERN_WARNING "tried to kill an mm-less task!\n");
                task_unlock(p);
                return;
        }
        task_unlock(p);
        printk(KERN_ERR "%s: Killed process %d (%s).\n",
                                message, p->pid, p->comm);

        /*
         * We give our sacrificial lamb high priority and access to
         * all the memory it needs. That way it should be able to
         * exit() and clear out its resources quickly...
         */
        p->time_slice = HZ;
        set_tsk_thread_flag(p, TIF_MEMDIE);

        force_sig(SIGKILL, p);
}

static struct mm_struct *oom_kill_task(task_t *p, const char *message)
{
        struct mm_struct *mm = get_task_mm(p);
        task_t * g, * q;

        if (!mm)
                return NULL;
        if (mm == &init_mm) {
                mmput(mm);
                return NULL;
        }

        __oom_kill_task(p, message);
        /*
         * kill all processes that share the ->mm (i.e. all threads),
         * but are in a different thread group
         */
        do_each_thread(g, q)
                if (q->mm == mm && q->tgid != p->tgid)
                        __oom_kill_task(q, message);
        while_each_thread(g, q);

        return mm;
}

static struct mm_struct *oom_kill_process(struct task_struct *p,
                                unsigned long points, const char *message)
{
        struct mm_struct *mm;
        struct task_struct *c;
        struct list_head *tsk;

        printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li and "
                "children.\n", p->pid, p->comm, points);
        /* Try to kill a child first */
        list_for_each(tsk, &p->children) {
                c = list_entry(tsk, struct task_struct, sibling);
                if (c->mm == p->mm)
                        continue;
                mm = oom_kill_task(c, message);
                if (mm)
                        return mm;
        }
        return oom_kill_task(p, message);
}

/**
 * oom_kill - kill the "best" process when we run out of memory
 *
 * 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)
{
        struct mm_struct *mm = NULL;
        task_t *p;
        unsigned long points = 0;

        if (printk_ratelimit()) {
                printk("oom-killer: gfp_mask=0x%x, order=%d\n",
                        gfp_mask, order);
                dump_stack();
                show_mem();
        }

        cpuset_lock();
        read_lock(&tasklist_lock);

        /*
         * Check if there were limitations on the allocation (only relevant for
         * NUMA) that may require different handling.
         */
        switch (constrained_alloc(zonelist, gfp_mask)) {
        case CONSTRAINT_MEMORY_POLICY:
                mm = oom_kill_process(current, points,
                                "No available memory (MPOL_BIND)");
                break;

        case CONSTRAINT_CPUSET:
                mm = oom_kill_process(current, points,
                                "No available memory in cpuset");
                break;

        case CONSTRAINT_NONE:
retry:
                /*
                 * Rambo mode: Shoot down a process and hope it solves whatever
                 * issues we may have.
                 */
                p = select_bad_process(&points);

                if (PTR_ERR(p) == -1UL)
                        goto out;

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

                mm = oom_kill_process(p, points, "Out of memory");
                if (!mm)
                        goto retry;

                break;
        }

out:
        read_unlock(&tasklist_lock);
        cpuset_unlock();
        if (mm)
                mmput(mm);

        /*
         * 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);
}