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7ba3485947
These days, if you swapoff when there isn't enough memory, OOM killer gives "BUG: scheduling while atomic" and the machine hangs: badness() needs to do its PF_SWAPOFF return after the task_unlock (tasklist_lock is also held here, so p isn't going to be freed: PF_SWAPOFF might get turned off at any moment, but that doesn't really matter). Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
467 lines
12 KiB
C
467 lines
12 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/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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int sysctl_panic_on_oom;
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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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{
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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 (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) ||
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p->uid == 0 || p->euid == 0)
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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 (cap_t(p->cap_effective) & CAP_TO_MASK(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_excl_nodes_overlap(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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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 %d 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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* Types of limitations to the nodes from which allocations may occur
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*/
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#define CONSTRAINT_NONE 1
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#define CONSTRAINT_MEMORY_POLICY 2
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#define CONSTRAINT_CPUSET 3
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/*
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* Determine the type of allocation constraint.
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*/
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static inline int constrained_alloc(struct zonelist *zonelist, 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;
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int node;
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/* node has memory ? */
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for_each_online_node(node)
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if (NODE_DATA(node)->node_present_pages)
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node_set(node, nodes);
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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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{
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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_init(p))
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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);
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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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* 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_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", p->pid, 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->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 && p->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 && q->tgid != p->tgid)
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force_sig(SIGKILL, p);
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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, unsigned long points,
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const char *message)
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{
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struct task_struct *c;
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struct list_head *tsk;
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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, p->pid, p->comm, points);
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/* Try to kill a child first */
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list_for_each(tsk, &p->children) {
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c = list_entry(tsk, struct task_struct, 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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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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* 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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{
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struct task_struct *p;
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unsigned long points = 0;
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unsigned long freed = 0;
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blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
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if (freed > 0)
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/* Got some memory back in the last second. */
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return;
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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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}
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cpuset_lock();
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read_lock(&tasklist_lock);
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/*
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* Check if there were limitations on the allocation (only relevant for
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* NUMA) that may require different handling.
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*/
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switch (constrained_alloc(zonelist, gfp_mask)) {
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case CONSTRAINT_MEMORY_POLICY:
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oom_kill_process(current, points,
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"No available memory (MPOL_BIND)");
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break;
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case CONSTRAINT_CPUSET:
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oom_kill_process(current, points,
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"No available memory in cpuset");
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break;
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case CONSTRAINT_NONE:
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if (sysctl_panic_on_oom)
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panic("out of memory. panic_on_oom is selected\n");
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retry:
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/*
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* Rambo mode: Shoot down a process and hope it solves whatever
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* issues we may have.
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*/
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p = select_bad_process(&points);
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if (PTR_ERR(p) == -1UL)
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goto out;
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/* Found nothing?!?! Either we hang forever, or we panic. */
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if (!p) {
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read_unlock(&tasklist_lock);
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cpuset_unlock();
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panic("Out of memory and no killable processes...\n");
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}
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if (oom_kill_process(p, points, "Out of memory"))
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goto retry;
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break;
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}
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out:
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read_unlock(&tasklist_lock);
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cpuset_unlock();
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/*
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* Give "p" a good chance of killing itself before we
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* retry to allocate memory unless "p" is current
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*/
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if (!test_thread_flag(TIF_MEMDIE))
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schedule_timeout_uninterruptible(1);
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}
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