![David Rientjes](/assets/img/avatar_default.png)
Adds a new sysctl, 'oom_dump_tasks', that enables the kernel to produce a dump of all system tasks (excluding kernel threads) when performing an OOM-killing. Information includes pid, uid, tgid, vm size, rss, cpu, oom_adj score, and name. This is helpful for determining why there was an OOM condition and which rogue task caused it. It is configurable so that large systems, such as those with several thousand tasks, do not incur a performance penalty associated with dumping data they may not desire. If an OOM was triggered as a result of a memory controller, the tasklist shall be filtered to exclude tasks that are not a member of the same cgroup. Cc: Andrea Arcangeli <andrea@suse.de> Cc: Christoph Lameter <clameter@sgi.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
584 lines
15 KiB
C
584 lines
15 KiB
C
/*
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* linux/mm/oom_kill.c
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*
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* Copyright (C) 1998,2000 Rik van Riel
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* Thanks go out to Claus Fischer for some serious inspiration and
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* for goading me into coding this file...
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*
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* The routines in this file are used to kill a process when
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* we're seriously out of memory. This gets called from __alloc_pages()
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* in mm/page_alloc.c when we really run out of memory.
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*
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* Since we won't call these routines often (on a well-configured
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* machine) this file will double as a 'coding guide' and a signpost
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* for newbie kernel hackers. It features several pointers to major
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* kernel subsystems and hints as to where to find out what things do.
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*/
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#include <linux/oom.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/sched.h>
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#include <linux/swap.h>
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#include <linux/timex.h>
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#include <linux/jiffies.h>
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#include <linux/cpuset.h>
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#include <linux/module.h>
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#include <linux/notifier.h>
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#include <linux/memcontrol.h>
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int sysctl_panic_on_oom;
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int sysctl_oom_kill_allocating_task;
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int sysctl_oom_dump_tasks;
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static DEFINE_SPINLOCK(zone_scan_mutex);
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/* #define DEBUG */
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/**
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* badness - calculate a numeric value for how bad this task has been
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* @p: task struct of which task we should calculate
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* @uptime: current uptime in seconds
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*
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* The formula used is relatively simple and documented inline in the
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* function. The main rationale is that we want to select a good task
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* to kill when we run out of memory.
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*
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* Good in this context means that:
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* 1) we lose the minimum amount of work done
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* 2) we recover a large amount of memory
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* 3) we don't kill anything innocent of eating tons of memory
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* 4) we want to kill the minimum amount of processes (one)
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* 5) we try to kill the process the user expects us to kill, this
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* algorithm has been meticulously tuned to meet the principle
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* of least surprise ... (be careful when you change it)
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*/
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unsigned long badness(struct task_struct *p, unsigned long uptime,
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struct mem_cgroup *mem)
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{
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unsigned long points, cpu_time, run_time, s;
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struct mm_struct *mm;
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struct task_struct *child;
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task_lock(p);
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mm = p->mm;
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if (!mm) {
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task_unlock(p);
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return 0;
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}
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/*
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* The memory size of the process is the basis for the badness.
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*/
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points = mm->total_vm;
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/*
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* After this unlock we can no longer dereference local variable `mm'
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*/
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task_unlock(p);
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/*
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* swapoff can easily use up all memory, so kill those first.
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*/
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if (p->flags & PF_SWAPOFF)
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return ULONG_MAX;
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/*
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* Processes which fork a lot of child processes are likely
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* a good choice. We add half the vmsize of the children if they
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* have an own mm. This prevents forking servers to flood the
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* machine with an endless amount of children. In case a single
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* child is eating the vast majority of memory, adding only half
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* to the parents will make the child our kill candidate of choice.
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*/
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list_for_each_entry(child, &p->children, sibling) {
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task_lock(child);
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if (child->mm != mm && child->mm)
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points += child->mm->total_vm/2 + 1;
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task_unlock(child);
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}
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/*
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* CPU time is in tens of seconds and run time is in thousands
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* of seconds. There is no particular reason for this other than
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* that it turned out to work very well in practice.
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*/
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cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime))
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>> (SHIFT_HZ + 3);
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if (uptime >= p->start_time.tv_sec)
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run_time = (uptime - p->start_time.tv_sec) >> 10;
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else
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run_time = 0;
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s = int_sqrt(cpu_time);
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if (s)
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points /= s;
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s = int_sqrt(int_sqrt(run_time));
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if (s)
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points /= s;
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/*
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* Niced processes are most likely less important, so double
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* their badness points.
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*/
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if (task_nice(p) > 0)
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points *= 2;
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/*
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* Superuser processes are usually more important, so we make it
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* less likely that we kill those.
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*/
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if (__capable(p, CAP_SYS_ADMIN) || __capable(p, CAP_SYS_RESOURCE))
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points /= 4;
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/*
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* We don't want to kill a process with direct hardware access.
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* Not only could that mess up the hardware, but usually users
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* tend to only have this flag set on applications they think
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* of as important.
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*/
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if (__capable(p, CAP_SYS_RAWIO))
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points /= 4;
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/*
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* If p's nodes don't overlap ours, it may still help to kill p
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* because p may have allocated or otherwise mapped memory on
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* this node before. However it will be less likely.
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*/
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if (!cpuset_mems_allowed_intersects(current, p))
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points /= 8;
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/*
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* Adjust the score by oomkilladj.
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*/
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if (p->oomkilladj) {
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if (p->oomkilladj > 0) {
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if (!points)
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points = 1;
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points <<= p->oomkilladj;
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} else
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points >>= -(p->oomkilladj);
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}
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#ifdef DEBUG
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printk(KERN_DEBUG "OOMkill: task %d (%s) got %lu points\n",
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p->pid, p->comm, points);
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#endif
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return points;
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}
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/*
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* Determine the type of allocation constraint.
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*/
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static inline enum oom_constraint constrained_alloc(struct zonelist *zonelist,
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gfp_t gfp_mask)
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{
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#ifdef CONFIG_NUMA
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struct zone **z;
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nodemask_t nodes = node_states[N_HIGH_MEMORY];
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for (z = zonelist->zones; *z; z++)
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if (cpuset_zone_allowed_softwall(*z, gfp_mask))
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node_clear(zone_to_nid(*z), nodes);
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else
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return CONSTRAINT_CPUSET;
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if (!nodes_empty(nodes))
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return CONSTRAINT_MEMORY_POLICY;
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#endif
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return CONSTRAINT_NONE;
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}
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/*
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* Simple selection loop. We chose the process with the highest
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* number of 'points'. We expect the caller will lock the tasklist.
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*
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* (not docbooked, we don't want this one cluttering up the manual)
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*/
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static struct task_struct *select_bad_process(unsigned long *ppoints,
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struct mem_cgroup *mem)
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{
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struct task_struct *g, *p;
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struct task_struct *chosen = NULL;
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struct timespec uptime;
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*ppoints = 0;
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do_posix_clock_monotonic_gettime(&uptime);
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do_each_thread(g, p) {
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unsigned long points;
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/*
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* skip kernel threads and tasks which have already released
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* their mm.
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*/
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if (!p->mm)
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continue;
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/* skip the init task */
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if (is_global_init(p))
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continue;
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if (mem && !task_in_mem_cgroup(p, mem))
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continue;
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/*
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* This task already has access to memory reserves and is
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* being killed. Don't allow any other task access to the
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* memory reserve.
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*
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* Note: this may have a chance of deadlock if it gets
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* blocked waiting for another task which itself is waiting
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* for memory. Is there a better alternative?
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*/
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if (test_tsk_thread_flag(p, TIF_MEMDIE))
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return ERR_PTR(-1UL);
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/*
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* This is in the process of releasing memory so wait for it
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* to finish before killing some other task by mistake.
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*
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* However, if p is the current task, we allow the 'kill' to
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* go ahead if it is exiting: this will simply set TIF_MEMDIE,
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* which will allow it to gain access to memory reserves in
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* the process of exiting and releasing its resources.
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* Otherwise we could get an easy OOM deadlock.
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*/
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if (p->flags & PF_EXITING) {
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if (p != current)
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return ERR_PTR(-1UL);
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chosen = p;
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*ppoints = ULONG_MAX;
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}
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if (p->oomkilladj == OOM_DISABLE)
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continue;
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points = badness(p, uptime.tv_sec, mem);
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if (points > *ppoints || !chosen) {
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chosen = p;
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*ppoints = points;
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}
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} while_each_thread(g, p);
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return chosen;
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}
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/**
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* Dumps the current memory state of all system tasks, excluding kernel threads.
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* State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
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* score, and name.
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*
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* If the actual is non-NULL, only tasks that are a member of the mem_cgroup are
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* shown.
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*
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* Call with tasklist_lock read-locked.
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*/
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static void dump_tasks(const struct mem_cgroup *mem)
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{
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struct task_struct *g, *p;
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printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj "
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"name\n");
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do_each_thread(g, p) {
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/*
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* total_vm and rss sizes do not exist for tasks with a
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* detached mm so there's no need to report them.
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*/
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if (!p->mm)
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continue;
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if (mem && !task_in_mem_cgroup(p, mem))
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continue;
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task_lock(p);
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printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n",
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p->pid, p->uid, p->tgid, p->mm->total_vm,
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get_mm_rss(p->mm), (int)task_cpu(p), p->oomkilladj,
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p->comm);
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task_unlock(p);
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} while_each_thread(g, p);
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}
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/**
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* Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO
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* flag though it's unlikely that we select a process with CAP_SYS_RAW_IO
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* set.
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*/
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static void __oom_kill_task(struct task_struct *p, int verbose)
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{
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if (is_global_init(p)) {
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WARN_ON(1);
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printk(KERN_WARNING "tried to kill init!\n");
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return;
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}
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if (!p->mm) {
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WARN_ON(1);
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printk(KERN_WARNING "tried to kill an mm-less task!\n");
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return;
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}
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if (verbose)
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printk(KERN_ERR "Killed process %d (%s)\n",
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task_pid_nr(p), p->comm);
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/*
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* We give our sacrificial lamb high priority and access to
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* all the memory it needs. That way it should be able to
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* exit() and clear out its resources quickly...
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*/
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p->rt.time_slice = HZ;
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set_tsk_thread_flag(p, TIF_MEMDIE);
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force_sig(SIGKILL, p);
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}
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static int oom_kill_task(struct task_struct *p)
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{
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struct mm_struct *mm;
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struct task_struct *g, *q;
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mm = p->mm;
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/* WARNING: mm may not be dereferenced since we did not obtain its
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* value from get_task_mm(p). This is OK since all we need to do is
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* compare mm to q->mm below.
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*
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* Furthermore, even if mm contains a non-NULL value, p->mm may
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* change to NULL at any time since we do not hold task_lock(p).
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* However, this is of no concern to us.
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*/
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if (mm == NULL)
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return 1;
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/*
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* Don't kill the process if any threads are set to OOM_DISABLE
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*/
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do_each_thread(g, q) {
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if (q->mm == mm && q->oomkilladj == OOM_DISABLE)
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return 1;
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} while_each_thread(g, q);
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__oom_kill_task(p, 1);
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/*
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* kill all processes that share the ->mm (i.e. all threads),
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* but are in a different thread group. Don't let them have access
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* to memory reserves though, otherwise we might deplete all memory.
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*/
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do_each_thread(g, q) {
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if (q->mm == mm && !same_thread_group(q, p))
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force_sig(SIGKILL, q);
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} while_each_thread(g, q);
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return 0;
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}
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static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
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unsigned long points, struct mem_cgroup *mem,
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const char *message)
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{
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struct task_struct *c;
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if (printk_ratelimit()) {
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printk(KERN_WARNING "%s invoked oom-killer: "
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"gfp_mask=0x%x, order=%d, oomkilladj=%d\n",
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current->comm, gfp_mask, order, current->oomkilladj);
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dump_stack();
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show_mem();
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if (sysctl_oom_dump_tasks)
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dump_tasks(mem);
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}
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/*
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* If the task is already exiting, don't alarm the sysadmin or kill
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* its children or threads, just set TIF_MEMDIE so it can die quickly
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*/
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if (p->flags & PF_EXITING) {
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__oom_kill_task(p, 0);
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return 0;
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}
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printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n",
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message, task_pid_nr(p), p->comm, points);
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/* Try to kill a child first */
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list_for_each_entry(c, &p->children, sibling) {
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if (c->mm == p->mm)
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continue;
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if (!oom_kill_task(c))
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return 0;
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}
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return oom_kill_task(p);
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}
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#ifdef CONFIG_CGROUP_MEM_CONT
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void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
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{
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unsigned long points = 0;
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struct task_struct *p;
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cgroup_lock();
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rcu_read_lock();
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retry:
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p = select_bad_process(&points, mem);
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if (PTR_ERR(p) == -1UL)
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goto out;
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if (!p)
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p = current;
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if (oom_kill_process(p, gfp_mask, 0, points, mem,
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"Memory cgroup out of memory"))
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goto retry;
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out:
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rcu_read_unlock();
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cgroup_unlock();
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}
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#endif
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static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
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int register_oom_notifier(struct notifier_block *nb)
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{
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return blocking_notifier_chain_register(&oom_notify_list, nb);
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}
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EXPORT_SYMBOL_GPL(register_oom_notifier);
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int unregister_oom_notifier(struct notifier_block *nb)
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{
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return blocking_notifier_chain_unregister(&oom_notify_list, nb);
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}
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EXPORT_SYMBOL_GPL(unregister_oom_notifier);
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|
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/*
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* Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
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* if a parallel OOM killing is already taking place that includes a zone in
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* the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
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*/
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int try_set_zone_oom(struct zonelist *zonelist)
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{
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struct zone **z;
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int ret = 1;
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z = zonelist->zones;
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|
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spin_lock(&zone_scan_mutex);
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do {
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if (zone_is_oom_locked(*z)) {
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ret = 0;
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goto out;
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}
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} while (*(++z) != NULL);
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|
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/*
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* Lock each zone in the zonelist under zone_scan_mutex so a parallel
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* invocation of try_set_zone_oom() doesn't succeed when it shouldn't.
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*/
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z = zonelist->zones;
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do {
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zone_set_flag(*z, ZONE_OOM_LOCKED);
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} while (*(++z) != NULL);
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out:
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spin_unlock(&zone_scan_mutex);
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return ret;
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}
|
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|
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/*
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* Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
|
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* allocation attempts with zonelists containing them may now recall the OOM
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* killer, if necessary.
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*/
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void clear_zonelist_oom(struct zonelist *zonelist)
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{
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struct zone **z;
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z = zonelist->zones;
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|
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spin_lock(&zone_scan_mutex);
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do {
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zone_clear_flag(*z, ZONE_OOM_LOCKED);
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} while (*(++z) != NULL);
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spin_unlock(&zone_scan_mutex);
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}
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|
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/**
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* out_of_memory - kill the "best" process when we run out of memory
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*
|
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* If we run out of memory, we have the choice between either
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* killing a random task (bad), letting the system crash (worse)
|
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* OR try to be smart about which process to kill. Note that we
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* don't have to be perfect here, we just have to be good.
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*/
|
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void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
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{
|
|
struct task_struct *p;
|
|
unsigned long points = 0;
|
|
unsigned long freed = 0;
|
|
enum oom_constraint constraint;
|
|
|
|
blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
|
|
if (freed > 0)
|
|
/* Got some memory back in the last second. */
|
|
return;
|
|
|
|
if (sysctl_panic_on_oom == 2)
|
|
panic("out of memory. Compulsory panic_on_oom is selected.\n");
|
|
|
|
/*
|
|
* Check if there were limitations on the allocation (only relevant for
|
|
* NUMA) that may require different handling.
|
|
*/
|
|
constraint = constrained_alloc(zonelist, gfp_mask);
|
|
read_lock(&tasklist_lock);
|
|
|
|
switch (constraint) {
|
|
case CONSTRAINT_MEMORY_POLICY:
|
|
oom_kill_process(current, gfp_mask, order, points, NULL,
|
|
"No available memory (MPOL_BIND)");
|
|
break;
|
|
|
|
case CONSTRAINT_NONE:
|
|
if (sysctl_panic_on_oom)
|
|
panic("out of memory. panic_on_oom is selected\n");
|
|
/* Fall-through */
|
|
case CONSTRAINT_CPUSET:
|
|
if (sysctl_oom_kill_allocating_task) {
|
|
oom_kill_process(current, gfp_mask, order, points, NULL,
|
|
"Out of memory (oom_kill_allocating_task)");
|
|
break;
|
|
}
|
|
retry:
|
|
/*
|
|
* Rambo mode: Shoot down a process and hope it solves whatever
|
|
* issues we may have.
|
|
*/
|
|
p = select_bad_process(&points, NULL);
|
|
|
|
if (PTR_ERR(p) == -1UL)
|
|
goto out;
|
|
|
|
/* Found nothing?!?! Either we hang forever, or we panic. */
|
|
if (!p) {
|
|
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;
|
|
|
|
break;
|
|
}
|
|
|
|
out:
|
|
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);
|
|
}
|