4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
31 #include <linux/nsproxy.h>
32 #include <linux/capability.h>
33 #include <linux/cpu.h>
34 #include <linux/cgroup.h>
35 #include <linux/security.h>
36 #include <linux/hugetlb.h>
37 #include <linux/swap.h>
38 #include <linux/syscalls.h>
39 #include <linux/jiffies.h>
40 #include <linux/tracehook.h>
41 #include <linux/futex.h>
42 #include <linux/compat.h>
43 #include <linux/task_io_accounting_ops.h>
44 #include <linux/rcupdate.h>
45 #include <linux/ptrace.h>
46 #include <linux/mount.h>
47 #include <linux/audit.h>
48 #include <linux/memcontrol.h>
49 #include <linux/ftrace.h>
50 #include <linux/profile.h>
51 #include <linux/rmap.h>
52 #include <linux/acct.h>
53 #include <linux/tsacct_kern.h>
54 #include <linux/cn_proc.h>
55 #include <linux/freezer.h>
56 #include <linux/delayacct.h>
57 #include <linux/taskstats_kern.h>
58 #include <linux/random.h>
59 #include <linux/tty.h>
60 #include <linux/proc_fs.h>
61 #include <linux/blkdev.h>
62 #include <linux/fs_struct.h>
63 #include <linux/magic.h>
64 #include <linux/perf_event.h>
66 #include <asm/pgtable.h>
67 #include <asm/pgalloc.h>
68 #include <asm/uaccess.h>
69 #include <asm/mmu_context.h>
70 #include <asm/cacheflush.h>
71 #include <asm/tlbflush.h>
73 #include <trace/events/sched.h>
76 * Protected counters by write_lock_irq(&tasklist_lock)
78 unsigned long total_forks; /* Handle normal Linux uptimes. */
79 int nr_threads; /* The idle threads do not count.. */
81 int max_threads; /* tunable limit on nr_threads */
83 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
85 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
87 int nr_processes(void)
92 for_each_online_cpu(cpu)
93 total += per_cpu(process_counts, cpu);
98 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
99 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
100 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
101 static struct kmem_cache *task_struct_cachep;
104 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
105 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
107 #ifdef CONFIG_DEBUG_STACK_USAGE
108 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
110 gfp_t mask = GFP_KERNEL;
112 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
115 static inline void free_thread_info(struct thread_info *ti)
117 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
121 /* SLAB cache for signal_struct structures (tsk->signal) */
122 static struct kmem_cache *signal_cachep;
124 /* SLAB cache for sighand_struct structures (tsk->sighand) */
125 struct kmem_cache *sighand_cachep;
127 /* SLAB cache for files_struct structures (tsk->files) */
128 struct kmem_cache *files_cachep;
130 /* SLAB cache for fs_struct structures (tsk->fs) */
131 struct kmem_cache *fs_cachep;
133 /* SLAB cache for vm_area_struct structures */
134 struct kmem_cache *vm_area_cachep;
136 /* SLAB cache for mm_struct structures (tsk->mm) */
137 static struct kmem_cache *mm_cachep;
139 static void account_kernel_stack(struct thread_info *ti, int account)
141 struct zone *zone = page_zone(virt_to_page(ti));
143 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
146 void free_task(struct task_struct *tsk)
148 prop_local_destroy_single(&tsk->dirties);
149 account_kernel_stack(tsk->stack, -1);
150 free_thread_info(tsk->stack);
151 rt_mutex_debug_task_free(tsk);
152 ftrace_graph_exit_task(tsk);
153 free_task_struct(tsk);
155 EXPORT_SYMBOL(free_task);
157 void __put_task_struct(struct task_struct *tsk)
159 WARN_ON(!tsk->exit_state);
160 WARN_ON(atomic_read(&tsk->usage));
161 WARN_ON(tsk == current);
164 delayacct_tsk_free(tsk);
166 if (!profile_handoff_task(tsk))
171 * macro override instead of weak attribute alias, to workaround
172 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
174 #ifndef arch_task_cache_init
175 #define arch_task_cache_init()
178 void __init fork_init(unsigned long mempages)
180 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
181 #ifndef ARCH_MIN_TASKALIGN
182 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
184 /* create a slab on which task_structs can be allocated */
186 kmem_cache_create("task_struct", sizeof(struct task_struct),
187 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
190 /* do the arch specific task caches init */
191 arch_task_cache_init();
194 * The default maximum number of threads is set to a safe
195 * value: the thread structures can take up at most half
198 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
201 * we need to allow at least 20 threads to boot a system
206 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
207 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
208 init_task.signal->rlim[RLIMIT_SIGPENDING] =
209 init_task.signal->rlim[RLIMIT_NPROC];
212 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
213 struct task_struct *src)
219 static struct task_struct *dup_task_struct(struct task_struct *orig)
221 struct task_struct *tsk;
222 struct thread_info *ti;
223 unsigned long *stackend;
227 prepare_to_copy(orig);
229 tsk = alloc_task_struct();
233 ti = alloc_thread_info(tsk);
235 free_task_struct(tsk);
239 err = arch_dup_task_struct(tsk, orig);
245 err = prop_local_init_single(&tsk->dirties);
249 setup_thread_stack(tsk, orig);
250 stackend = end_of_stack(tsk);
251 *stackend = STACK_END_MAGIC; /* for overflow detection */
253 #ifdef CONFIG_CC_STACKPROTECTOR
254 tsk->stack_canary = get_random_int();
257 /* One for us, one for whoever does the "release_task()" (usually parent) */
258 atomic_set(&tsk->usage,2);
259 atomic_set(&tsk->fs_excl, 0);
260 #ifdef CONFIG_BLK_DEV_IO_TRACE
263 tsk->splice_pipe = NULL;
265 account_kernel_stack(ti, 1);
270 free_thread_info(ti);
271 free_task_struct(tsk);
276 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
278 struct vm_area_struct *mpnt, *tmp, **pprev;
279 struct rb_node **rb_link, *rb_parent;
281 unsigned long charge;
282 struct mempolicy *pol;
284 down_write(&oldmm->mmap_sem);
285 flush_cache_dup_mm(oldmm);
287 * Not linked in yet - no deadlock potential:
289 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
293 mm->mmap_cache = NULL;
294 mm->free_area_cache = oldmm->mmap_base;
295 mm->cached_hole_size = ~0UL;
297 cpumask_clear(mm_cpumask(mm));
299 rb_link = &mm->mm_rb.rb_node;
303 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
306 if (mpnt->vm_flags & VM_DONTCOPY) {
307 long pages = vma_pages(mpnt);
308 mm->total_vm -= pages;
309 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
314 if (mpnt->vm_flags & VM_ACCOUNT) {
315 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
316 if (security_vm_enough_memory(len))
320 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
324 pol = mpol_dup(vma_policy(mpnt));
325 retval = PTR_ERR(pol);
327 goto fail_nomem_policy;
328 vma_set_policy(tmp, pol);
329 tmp->vm_flags &= ~VM_LOCKED;
335 struct inode *inode = file->f_path.dentry->d_inode;
336 struct address_space *mapping = file->f_mapping;
339 if (tmp->vm_flags & VM_DENYWRITE)
340 atomic_dec(&inode->i_writecount);
341 spin_lock(&mapping->i_mmap_lock);
342 if (tmp->vm_flags & VM_SHARED)
343 mapping->i_mmap_writable++;
344 tmp->vm_truncate_count = mpnt->vm_truncate_count;
345 flush_dcache_mmap_lock(mapping);
346 /* insert tmp into the share list, just after mpnt */
347 vma_prio_tree_add(tmp, mpnt);
348 flush_dcache_mmap_unlock(mapping);
349 spin_unlock(&mapping->i_mmap_lock);
353 * Clear hugetlb-related page reserves for children. This only
354 * affects MAP_PRIVATE mappings. Faults generated by the child
355 * are not guaranteed to succeed, even if read-only
357 if (is_vm_hugetlb_page(tmp))
358 reset_vma_resv_huge_pages(tmp);
361 * Link in the new vma and copy the page table entries.
364 pprev = &tmp->vm_next;
366 __vma_link_rb(mm, tmp, rb_link, rb_parent);
367 rb_link = &tmp->vm_rb.rb_right;
368 rb_parent = &tmp->vm_rb;
371 retval = copy_page_range(mm, oldmm, mpnt);
373 if (tmp->vm_ops && tmp->vm_ops->open)
374 tmp->vm_ops->open(tmp);
379 /* a new mm has just been created */
380 arch_dup_mmap(oldmm, mm);
383 up_write(&mm->mmap_sem);
385 up_write(&oldmm->mmap_sem);
388 kmem_cache_free(vm_area_cachep, tmp);
391 vm_unacct_memory(charge);
395 static inline int mm_alloc_pgd(struct mm_struct * mm)
397 mm->pgd = pgd_alloc(mm);
398 if (unlikely(!mm->pgd))
403 static inline void mm_free_pgd(struct mm_struct * mm)
405 pgd_free(mm, mm->pgd);
408 #define dup_mmap(mm, oldmm) (0)
409 #define mm_alloc_pgd(mm) (0)
410 #define mm_free_pgd(mm)
411 #endif /* CONFIG_MMU */
413 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
415 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
416 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
418 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
420 static int __init coredump_filter_setup(char *s)
422 default_dump_filter =
423 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
424 MMF_DUMP_FILTER_MASK;
428 __setup("coredump_filter=", coredump_filter_setup);
430 #include <linux/init_task.h>
432 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
434 atomic_set(&mm->mm_users, 1);
435 atomic_set(&mm->mm_count, 1);
436 init_rwsem(&mm->mmap_sem);
437 INIT_LIST_HEAD(&mm->mmlist);
438 mm->flags = (current->mm) ? current->mm->flags : default_dump_filter;
439 mm->core_state = NULL;
441 set_mm_counter(mm, file_rss, 0);
442 set_mm_counter(mm, anon_rss, 0);
443 spin_lock_init(&mm->page_table_lock);
444 spin_lock_init(&mm->ioctx_lock);
445 INIT_HLIST_HEAD(&mm->ioctx_list);
446 mm->free_area_cache = TASK_UNMAPPED_BASE;
447 mm->cached_hole_size = ~0UL;
448 mm_init_owner(mm, p);
450 if (likely(!mm_alloc_pgd(mm))) {
452 mmu_notifier_mm_init(mm);
461 * Allocate and initialize an mm_struct.
463 struct mm_struct * mm_alloc(void)
465 struct mm_struct * mm;
469 memset(mm, 0, sizeof(*mm));
470 mm = mm_init(mm, current);
476 * Called when the last reference to the mm
477 * is dropped: either by a lazy thread or by
478 * mmput. Free the page directory and the mm.
480 void __mmdrop(struct mm_struct *mm)
482 BUG_ON(mm == &init_mm);
485 mmu_notifier_mm_destroy(mm);
488 EXPORT_SYMBOL_GPL(__mmdrop);
491 * Decrement the use count and release all resources for an mm.
493 void mmput(struct mm_struct *mm)
497 if (atomic_dec_and_test(&mm->mm_users)) {
500 set_mm_exe_file(mm, NULL);
501 if (!list_empty(&mm->mmlist)) {
502 spin_lock(&mmlist_lock);
503 list_del(&mm->mmlist);
504 spin_unlock(&mmlist_lock);
510 EXPORT_SYMBOL_GPL(mmput);
513 * get_task_mm - acquire a reference to the task's mm
515 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
516 * this kernel workthread has transiently adopted a user mm with use_mm,
517 * to do its AIO) is not set and if so returns a reference to it, after
518 * bumping up the use count. User must release the mm via mmput()
519 * after use. Typically used by /proc and ptrace.
521 struct mm_struct *get_task_mm(struct task_struct *task)
523 struct mm_struct *mm;
528 if (task->flags & PF_KTHREAD)
531 atomic_inc(&mm->mm_users);
536 EXPORT_SYMBOL_GPL(get_task_mm);
538 /* Please note the differences between mmput and mm_release.
539 * mmput is called whenever we stop holding onto a mm_struct,
540 * error success whatever.
542 * mm_release is called after a mm_struct has been removed
543 * from the current process.
545 * This difference is important for error handling, when we
546 * only half set up a mm_struct for a new process and need to restore
547 * the old one. Because we mmput the new mm_struct before
548 * restoring the old one. . .
549 * Eric Biederman 10 January 1998
551 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
553 struct completion *vfork_done = tsk->vfork_done;
555 /* Get rid of any futexes when releasing the mm */
557 if (unlikely(tsk->robust_list))
558 exit_robust_list(tsk);
560 if (unlikely(tsk->compat_robust_list))
561 compat_exit_robust_list(tsk);
565 /* Get rid of any cached register state */
566 deactivate_mm(tsk, mm);
568 /* notify parent sleeping on vfork() */
570 tsk->vfork_done = NULL;
571 complete(vfork_done);
575 * If we're exiting normally, clear a user-space tid field if
576 * requested. We leave this alone when dying by signal, to leave
577 * the value intact in a core dump, and to save the unnecessary
578 * trouble otherwise. Userland only wants this done for a sys_exit.
580 if (tsk->clear_child_tid) {
581 if (!(tsk->flags & PF_SIGNALED) &&
582 atomic_read(&mm->mm_users) > 1) {
584 * We don't check the error code - if userspace has
585 * not set up a proper pointer then tough luck.
587 put_user(0, tsk->clear_child_tid);
588 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
591 tsk->clear_child_tid = NULL;
596 * Allocate a new mm structure and copy contents from the
597 * mm structure of the passed in task structure.
599 struct mm_struct *dup_mm(struct task_struct *tsk)
601 struct mm_struct *mm, *oldmm = current->mm;
611 memcpy(mm, oldmm, sizeof(*mm));
613 /* Initializing for Swap token stuff */
614 mm->token_priority = 0;
615 mm->last_interval = 0;
617 if (!mm_init(mm, tsk))
620 if (init_new_context(tsk, mm))
623 dup_mm_exe_file(oldmm, mm);
625 err = dup_mmap(mm, oldmm);
629 mm->hiwater_rss = get_mm_rss(mm);
630 mm->hiwater_vm = mm->total_vm;
642 * If init_new_context() failed, we cannot use mmput() to free the mm
643 * because it calls destroy_context()
650 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
652 struct mm_struct * mm, *oldmm;
655 tsk->min_flt = tsk->maj_flt = 0;
656 tsk->nvcsw = tsk->nivcsw = 0;
657 #ifdef CONFIG_DETECT_HUNG_TASK
658 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
662 tsk->active_mm = NULL;
665 * Are we cloning a kernel thread?
667 * We need to steal a active VM for that..
673 if (clone_flags & CLONE_VM) {
674 atomic_inc(&oldmm->mm_users);
685 /* Initializing for Swap token stuff */
686 mm->token_priority = 0;
687 mm->last_interval = 0;
697 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
699 struct fs_struct *fs = current->fs;
700 if (clone_flags & CLONE_FS) {
701 /* tsk->fs is already what we want */
702 write_lock(&fs->lock);
704 write_unlock(&fs->lock);
708 write_unlock(&fs->lock);
711 tsk->fs = copy_fs_struct(fs);
717 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
719 struct files_struct *oldf, *newf;
723 * A background process may not have any files ...
725 oldf = current->files;
729 if (clone_flags & CLONE_FILES) {
730 atomic_inc(&oldf->count);
734 newf = dup_fd(oldf, &error);
744 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
747 struct io_context *ioc = current->io_context;
752 * Share io context with parent, if CLONE_IO is set
754 if (clone_flags & CLONE_IO) {
755 tsk->io_context = ioc_task_link(ioc);
756 if (unlikely(!tsk->io_context))
758 } else if (ioprio_valid(ioc->ioprio)) {
759 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
760 if (unlikely(!tsk->io_context))
763 tsk->io_context->ioprio = ioc->ioprio;
769 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
771 struct sighand_struct *sig;
773 if (clone_flags & CLONE_SIGHAND) {
774 atomic_inc(¤t->sighand->count);
777 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
778 rcu_assign_pointer(tsk->sighand, sig);
781 atomic_set(&sig->count, 1);
782 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
786 void __cleanup_sighand(struct sighand_struct *sighand)
788 if (atomic_dec_and_test(&sighand->count))
789 kmem_cache_free(sighand_cachep, sighand);
794 * Initialize POSIX timer handling for a thread group.
796 static void posix_cpu_timers_init_group(struct signal_struct *sig)
798 /* Thread group counters. */
799 thread_group_cputime_init(sig);
801 /* Expiration times and increments. */
802 sig->it_virt_expires = cputime_zero;
803 sig->it_virt_incr = cputime_zero;
804 sig->it_prof_expires = cputime_zero;
805 sig->it_prof_incr = cputime_zero;
807 /* Cached expiration times. */
808 sig->cputime_expires.prof_exp = cputime_zero;
809 sig->cputime_expires.virt_exp = cputime_zero;
810 sig->cputime_expires.sched_exp = 0;
812 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
813 sig->cputime_expires.prof_exp =
814 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
815 sig->cputimer.running = 1;
818 /* The timer lists. */
819 INIT_LIST_HEAD(&sig->cpu_timers[0]);
820 INIT_LIST_HEAD(&sig->cpu_timers[1]);
821 INIT_LIST_HEAD(&sig->cpu_timers[2]);
824 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
826 struct signal_struct *sig;
828 if (clone_flags & CLONE_THREAD)
831 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
836 atomic_set(&sig->count, 1);
837 atomic_set(&sig->live, 1);
838 init_waitqueue_head(&sig->wait_chldexit);
840 if (clone_flags & CLONE_NEWPID)
841 sig->flags |= SIGNAL_UNKILLABLE;
842 sig->group_exit_code = 0;
843 sig->group_exit_task = NULL;
844 sig->group_stop_count = 0;
845 sig->curr_target = tsk;
846 init_sigpending(&sig->shared_pending);
847 INIT_LIST_HEAD(&sig->posix_timers);
849 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
850 sig->it_real_incr.tv64 = 0;
851 sig->real_timer.function = it_real_fn;
853 sig->leader = 0; /* session leadership doesn't inherit */
854 sig->tty_old_pgrp = NULL;
857 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
858 sig->gtime = cputime_zero;
859 sig->cgtime = cputime_zero;
860 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
861 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
862 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
863 task_io_accounting_init(&sig->ioac);
864 sig->sum_sched_runtime = 0;
865 taskstats_tgid_init(sig);
867 task_lock(current->group_leader);
868 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
869 task_unlock(current->group_leader);
871 posix_cpu_timers_init_group(sig);
873 acct_init_pacct(&sig->pacct);
880 void __cleanup_signal(struct signal_struct *sig)
882 thread_group_cputime_free(sig);
883 tty_kref_put(sig->tty);
884 kmem_cache_free(signal_cachep, sig);
887 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
889 unsigned long new_flags = p->flags;
891 new_flags &= ~PF_SUPERPRIV;
892 new_flags |= PF_FORKNOEXEC;
893 new_flags |= PF_STARTING;
894 p->flags = new_flags;
895 clear_freeze_flag(p);
898 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
900 current->clear_child_tid = tidptr;
902 return task_pid_vnr(current);
905 static void rt_mutex_init_task(struct task_struct *p)
907 spin_lock_init(&p->pi_lock);
908 #ifdef CONFIG_RT_MUTEXES
909 plist_head_init(&p->pi_waiters, &p->pi_lock);
910 p->pi_blocked_on = NULL;
914 #ifdef CONFIG_MM_OWNER
915 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
919 #endif /* CONFIG_MM_OWNER */
922 * Initialize POSIX timer handling for a single task.
924 static void posix_cpu_timers_init(struct task_struct *tsk)
926 tsk->cputime_expires.prof_exp = cputime_zero;
927 tsk->cputime_expires.virt_exp = cputime_zero;
928 tsk->cputime_expires.sched_exp = 0;
929 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
930 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
931 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
935 * This creates a new process as a copy of the old one,
936 * but does not actually start it yet.
938 * It copies the registers, and all the appropriate
939 * parts of the process environment (as per the clone
940 * flags). The actual kick-off is left to the caller.
942 static struct task_struct *copy_process(unsigned long clone_flags,
943 unsigned long stack_start,
944 struct pt_regs *regs,
945 unsigned long stack_size,
946 int __user *child_tidptr,
951 struct task_struct *p;
952 int cgroup_callbacks_done = 0;
954 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
955 return ERR_PTR(-EINVAL);
958 * Thread groups must share signals as well, and detached threads
959 * can only be started up within the thread group.
961 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
962 return ERR_PTR(-EINVAL);
965 * Shared signal handlers imply shared VM. By way of the above,
966 * thread groups also imply shared VM. Blocking this case allows
967 * for various simplifications in other code.
969 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
970 return ERR_PTR(-EINVAL);
972 retval = security_task_create(clone_flags);
977 p = dup_task_struct(current);
981 ftrace_graph_init_task(p);
983 rt_mutex_init_task(p);
985 #ifdef CONFIG_PROVE_LOCKING
986 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
987 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
990 if (atomic_read(&p->real_cred->user->processes) >=
991 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
992 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
993 p->real_cred->user != INIT_USER)
997 retval = copy_creds(p, clone_flags);
1002 * If multiple threads are within copy_process(), then this check
1003 * triggers too late. This doesn't hurt, the check is only there
1004 * to stop root fork bombs.
1007 if (nr_threads >= max_threads)
1008 goto bad_fork_cleanup_count;
1010 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1011 goto bad_fork_cleanup_count;
1013 if (p->binfmt && !try_module_get(p->binfmt->module))
1014 goto bad_fork_cleanup_put_domain;
1017 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1018 copy_flags(clone_flags, p);
1019 INIT_LIST_HEAD(&p->children);
1020 INIT_LIST_HEAD(&p->sibling);
1021 rcu_copy_process(p);
1022 p->vfork_done = NULL;
1023 spin_lock_init(&p->alloc_lock);
1025 init_sigpending(&p->pending);
1027 p->utime = cputime_zero;
1028 p->stime = cputime_zero;
1029 p->gtime = cputime_zero;
1030 p->utimescaled = cputime_zero;
1031 p->stimescaled = cputime_zero;
1032 p->prev_utime = cputime_zero;
1033 p->prev_stime = cputime_zero;
1035 p->default_timer_slack_ns = current->timer_slack_ns;
1037 task_io_accounting_init(&p->ioac);
1038 acct_clear_integrals(p);
1040 posix_cpu_timers_init(p);
1042 p->lock_depth = -1; /* -1 = no lock */
1043 do_posix_clock_monotonic_gettime(&p->start_time);
1044 p->real_start_time = p->start_time;
1045 monotonic_to_bootbased(&p->real_start_time);
1046 p->io_context = NULL;
1047 p->audit_context = NULL;
1050 p->mempolicy = mpol_dup(p->mempolicy);
1051 if (IS_ERR(p->mempolicy)) {
1052 retval = PTR_ERR(p->mempolicy);
1053 p->mempolicy = NULL;
1054 goto bad_fork_cleanup_cgroup;
1056 mpol_fix_fork_child_flag(p);
1058 #ifdef CONFIG_TRACE_IRQFLAGS
1060 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1061 p->hardirqs_enabled = 1;
1063 p->hardirqs_enabled = 0;
1065 p->hardirq_enable_ip = 0;
1066 p->hardirq_enable_event = 0;
1067 p->hardirq_disable_ip = _THIS_IP_;
1068 p->hardirq_disable_event = 0;
1069 p->softirqs_enabled = 1;
1070 p->softirq_enable_ip = _THIS_IP_;
1071 p->softirq_enable_event = 0;
1072 p->softirq_disable_ip = 0;
1073 p->softirq_disable_event = 0;
1074 p->hardirq_context = 0;
1075 p->softirq_context = 0;
1077 #ifdef CONFIG_LOCKDEP
1078 p->lockdep_depth = 0; /* no locks held yet */
1079 p->curr_chain_key = 0;
1080 p->lockdep_recursion = 0;
1083 #ifdef CONFIG_DEBUG_MUTEXES
1084 p->blocked_on = NULL; /* not blocked yet */
1089 /* Perform scheduler related setup. Assign this task to a CPU. */
1090 sched_fork(p, clone_flags);
1092 retval = perf_event_init_task(p);
1094 goto bad_fork_cleanup_policy;
1096 if ((retval = audit_alloc(p)))
1097 goto bad_fork_cleanup_policy;
1098 /* copy all the process information */
1099 if ((retval = copy_semundo(clone_flags, p)))
1100 goto bad_fork_cleanup_audit;
1101 if ((retval = copy_files(clone_flags, p)))
1102 goto bad_fork_cleanup_semundo;
1103 if ((retval = copy_fs(clone_flags, p)))
1104 goto bad_fork_cleanup_files;
1105 if ((retval = copy_sighand(clone_flags, p)))
1106 goto bad_fork_cleanup_fs;
1107 if ((retval = copy_signal(clone_flags, p)))
1108 goto bad_fork_cleanup_sighand;
1109 if ((retval = copy_mm(clone_flags, p)))
1110 goto bad_fork_cleanup_signal;
1111 if ((retval = copy_namespaces(clone_flags, p)))
1112 goto bad_fork_cleanup_mm;
1113 if ((retval = copy_io(clone_flags, p)))
1114 goto bad_fork_cleanup_namespaces;
1115 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1117 goto bad_fork_cleanup_io;
1119 if (pid != &init_struct_pid) {
1121 pid = alloc_pid(p->nsproxy->pid_ns);
1123 goto bad_fork_cleanup_io;
1125 if (clone_flags & CLONE_NEWPID) {
1126 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1128 goto bad_fork_free_pid;
1132 p->pid = pid_nr(pid);
1134 if (clone_flags & CLONE_THREAD)
1135 p->tgid = current->tgid;
1137 if (current->nsproxy != p->nsproxy) {
1138 retval = ns_cgroup_clone(p, pid);
1140 goto bad_fork_free_pid;
1143 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1145 * Clear TID on mm_release()?
1147 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1149 p->robust_list = NULL;
1150 #ifdef CONFIG_COMPAT
1151 p->compat_robust_list = NULL;
1153 INIT_LIST_HEAD(&p->pi_state_list);
1154 p->pi_state_cache = NULL;
1157 * sigaltstack should be cleared when sharing the same VM
1159 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1160 p->sas_ss_sp = p->sas_ss_size = 0;
1163 * Syscall tracing should be turned off in the child regardless
1166 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1167 #ifdef TIF_SYSCALL_EMU
1168 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1170 clear_all_latency_tracing(p);
1172 /* ok, now we should be set up.. */
1173 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1174 p->pdeath_signal = 0;
1178 * Ok, make it visible to the rest of the system.
1179 * We dont wake it up yet.
1181 p->group_leader = p;
1182 INIT_LIST_HEAD(&p->thread_group);
1184 /* Now that the task is set up, run cgroup callbacks if
1185 * necessary. We need to run them before the task is visible
1186 * on the tasklist. */
1187 cgroup_fork_callbacks(p);
1188 cgroup_callbacks_done = 1;
1190 /* Need tasklist lock for parent etc handling! */
1191 write_lock_irq(&tasklist_lock);
1194 * The task hasn't been attached yet, so its cpus_allowed mask will
1195 * not be changed, nor will its assigned CPU.
1197 * The cpus_allowed mask of the parent may have changed after it was
1198 * copied first time - so re-copy it here, then check the child's CPU
1199 * to ensure it is on a valid CPU (and if not, just force it back to
1200 * parent's CPU). This avoids alot of nasty races.
1202 p->cpus_allowed = current->cpus_allowed;
1203 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1204 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1205 !cpu_online(task_cpu(p))))
1206 set_task_cpu(p, smp_processor_id());
1208 /* CLONE_PARENT re-uses the old parent */
1209 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1210 p->real_parent = current->real_parent;
1211 p->parent_exec_id = current->parent_exec_id;
1213 p->real_parent = current;
1214 p->parent_exec_id = current->self_exec_id;
1217 spin_lock(¤t->sighand->siglock);
1220 * Process group and session signals need to be delivered to just the
1221 * parent before the fork or both the parent and the child after the
1222 * fork. Restart if a signal comes in before we add the new process to
1223 * it's process group.
1224 * A fatal signal pending means that current will exit, so the new
1225 * thread can't slip out of an OOM kill (or normal SIGKILL).
1227 recalc_sigpending();
1228 if (signal_pending(current)) {
1229 spin_unlock(¤t->sighand->siglock);
1230 write_unlock_irq(&tasklist_lock);
1231 retval = -ERESTARTNOINTR;
1232 goto bad_fork_free_pid;
1235 if (clone_flags & CLONE_THREAD) {
1236 atomic_inc(¤t->signal->count);
1237 atomic_inc(¤t->signal->live);
1238 p->group_leader = current->group_leader;
1239 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1242 if (likely(p->pid)) {
1243 list_add_tail(&p->sibling, &p->real_parent->children);
1244 tracehook_finish_clone(p, clone_flags, trace);
1246 if (thread_group_leader(p)) {
1247 if (clone_flags & CLONE_NEWPID)
1248 p->nsproxy->pid_ns->child_reaper = p;
1250 p->signal->leader_pid = pid;
1251 tty_kref_put(p->signal->tty);
1252 p->signal->tty = tty_kref_get(current->signal->tty);
1253 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1254 attach_pid(p, PIDTYPE_SID, task_session(current));
1255 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1256 __get_cpu_var(process_counts)++;
1258 attach_pid(p, PIDTYPE_PID, pid);
1263 spin_unlock(¤t->sighand->siglock);
1264 write_unlock_irq(&tasklist_lock);
1265 proc_fork_connector(p);
1266 cgroup_post_fork(p);
1271 if (pid != &init_struct_pid)
1273 bad_fork_cleanup_io:
1274 put_io_context(p->io_context);
1275 bad_fork_cleanup_namespaces:
1276 exit_task_namespaces(p);
1277 bad_fork_cleanup_mm:
1280 bad_fork_cleanup_signal:
1281 if (!(clone_flags & CLONE_THREAD))
1282 __cleanup_signal(p->signal);
1283 bad_fork_cleanup_sighand:
1284 __cleanup_sighand(p->sighand);
1285 bad_fork_cleanup_fs:
1286 exit_fs(p); /* blocking */
1287 bad_fork_cleanup_files:
1288 exit_files(p); /* blocking */
1289 bad_fork_cleanup_semundo:
1291 bad_fork_cleanup_audit:
1293 bad_fork_cleanup_policy:
1294 perf_event_free_task(p);
1296 mpol_put(p->mempolicy);
1297 bad_fork_cleanup_cgroup:
1299 cgroup_exit(p, cgroup_callbacks_done);
1300 delayacct_tsk_free(p);
1302 module_put(p->binfmt->module);
1303 bad_fork_cleanup_put_domain:
1304 module_put(task_thread_info(p)->exec_domain->module);
1305 bad_fork_cleanup_count:
1306 atomic_dec(&p->cred->user->processes);
1311 return ERR_PTR(retval);
1314 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1316 memset(regs, 0, sizeof(struct pt_regs));
1320 struct task_struct * __cpuinit fork_idle(int cpu)
1322 struct task_struct *task;
1323 struct pt_regs regs;
1325 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL,
1326 &init_struct_pid, 0);
1328 init_idle(task, cpu);
1334 * Ok, this is the main fork-routine.
1336 * It copies the process, and if successful kick-starts
1337 * it and waits for it to finish using the VM if required.
1339 long do_fork(unsigned long clone_flags,
1340 unsigned long stack_start,
1341 struct pt_regs *regs,
1342 unsigned long stack_size,
1343 int __user *parent_tidptr,
1344 int __user *child_tidptr)
1346 struct task_struct *p;
1351 * Do some preliminary argument and permissions checking before we
1352 * actually start allocating stuff
1354 if (clone_flags & CLONE_NEWUSER) {
1355 if (clone_flags & CLONE_THREAD)
1357 /* hopefully this check will go away when userns support is
1360 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1361 !capable(CAP_SETGID))
1366 * We hope to recycle these flags after 2.6.26
1368 if (unlikely(clone_flags & CLONE_STOPPED)) {
1369 static int __read_mostly count = 100;
1371 if (count > 0 && printk_ratelimit()) {
1372 char comm[TASK_COMM_LEN];
1375 printk(KERN_INFO "fork(): process `%s' used deprecated "
1376 "clone flags 0x%lx\n",
1377 get_task_comm(comm, current),
1378 clone_flags & CLONE_STOPPED);
1383 * When called from kernel_thread, don't do user tracing stuff.
1385 if (likely(user_mode(regs)))
1386 trace = tracehook_prepare_clone(clone_flags);
1388 p = copy_process(clone_flags, stack_start, regs, stack_size,
1389 child_tidptr, NULL, trace);
1391 * Do this prior waking up the new thread - the thread pointer
1392 * might get invalid after that point, if the thread exits quickly.
1395 struct completion vfork;
1397 trace_sched_process_fork(current, p);
1399 nr = task_pid_vnr(p);
1401 if (clone_flags & CLONE_PARENT_SETTID)
1402 put_user(nr, parent_tidptr);
1404 if (clone_flags & CLONE_VFORK) {
1405 p->vfork_done = &vfork;
1406 init_completion(&vfork);
1409 audit_finish_fork(p);
1410 tracehook_report_clone(regs, clone_flags, nr, p);
1413 * We set PF_STARTING at creation in case tracing wants to
1414 * use this to distinguish a fully live task from one that
1415 * hasn't gotten to tracehook_report_clone() yet. Now we
1416 * clear it and set the child going.
1418 p->flags &= ~PF_STARTING;
1420 if (unlikely(clone_flags & CLONE_STOPPED)) {
1422 * We'll start up with an immediate SIGSTOP.
1424 sigaddset(&p->pending.signal, SIGSTOP);
1425 set_tsk_thread_flag(p, TIF_SIGPENDING);
1426 __set_task_state(p, TASK_STOPPED);
1428 wake_up_new_task(p, clone_flags);
1431 tracehook_report_clone_complete(trace, regs,
1432 clone_flags, nr, p);
1434 if (clone_flags & CLONE_VFORK) {
1435 freezer_do_not_count();
1436 wait_for_completion(&vfork);
1438 tracehook_report_vfork_done(p, nr);
1446 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1447 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1450 static void sighand_ctor(void *data)
1452 struct sighand_struct *sighand = data;
1454 spin_lock_init(&sighand->siglock);
1455 init_waitqueue_head(&sighand->signalfd_wqh);
1458 void __init proc_caches_init(void)
1460 sighand_cachep = kmem_cache_create("sighand_cache",
1461 sizeof(struct sighand_struct), 0,
1462 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1463 SLAB_NOTRACK, sighand_ctor);
1464 signal_cachep = kmem_cache_create("signal_cache",
1465 sizeof(struct signal_struct), 0,
1466 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1467 files_cachep = kmem_cache_create("files_cache",
1468 sizeof(struct files_struct), 0,
1469 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1470 fs_cachep = kmem_cache_create("fs_cache",
1471 sizeof(struct fs_struct), 0,
1472 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1473 mm_cachep = kmem_cache_create("mm_struct",
1474 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1475 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1476 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1481 * Check constraints on flags passed to the unshare system call and
1482 * force unsharing of additional process context as appropriate.
1484 static void check_unshare_flags(unsigned long *flags_ptr)
1487 * If unsharing a thread from a thread group, must also
1490 if (*flags_ptr & CLONE_THREAD)
1491 *flags_ptr |= CLONE_VM;
1494 * If unsharing vm, must also unshare signal handlers.
1496 if (*flags_ptr & CLONE_VM)
1497 *flags_ptr |= CLONE_SIGHAND;
1500 * If unsharing signal handlers and the task was created
1501 * using CLONE_THREAD, then must unshare the thread
1503 if ((*flags_ptr & CLONE_SIGHAND) &&
1504 (atomic_read(¤t->signal->count) > 1))
1505 *flags_ptr |= CLONE_THREAD;
1508 * If unsharing namespace, must also unshare filesystem information.
1510 if (*flags_ptr & CLONE_NEWNS)
1511 *flags_ptr |= CLONE_FS;
1515 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1517 static int unshare_thread(unsigned long unshare_flags)
1519 if (unshare_flags & CLONE_THREAD)
1526 * Unshare the filesystem structure if it is being shared
1528 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1530 struct fs_struct *fs = current->fs;
1532 if (!(unshare_flags & CLONE_FS) || !fs)
1535 /* don't need lock here; in the worst case we'll do useless copy */
1539 *new_fsp = copy_fs_struct(fs);
1547 * Unsharing of sighand is not supported yet
1549 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1551 struct sighand_struct *sigh = current->sighand;
1553 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1560 * Unshare vm if it is being shared
1562 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1564 struct mm_struct *mm = current->mm;
1566 if ((unshare_flags & CLONE_VM) &&
1567 (mm && atomic_read(&mm->mm_users) > 1)) {
1575 * Unshare file descriptor table if it is being shared
1577 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1579 struct files_struct *fd = current->files;
1582 if ((unshare_flags & CLONE_FILES) &&
1583 (fd && atomic_read(&fd->count) > 1)) {
1584 *new_fdp = dup_fd(fd, &error);
1593 * unshare allows a process to 'unshare' part of the process
1594 * context which was originally shared using clone. copy_*
1595 * functions used by do_fork() cannot be used here directly
1596 * because they modify an inactive task_struct that is being
1597 * constructed. Here we are modifying the current, active,
1600 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1603 struct fs_struct *fs, *new_fs = NULL;
1604 struct sighand_struct *new_sigh = NULL;
1605 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1606 struct files_struct *fd, *new_fd = NULL;
1607 struct nsproxy *new_nsproxy = NULL;
1610 check_unshare_flags(&unshare_flags);
1612 /* Return -EINVAL for all unsupported flags */
1614 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1615 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1616 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1617 goto bad_unshare_out;
1620 * CLONE_NEWIPC must also detach from the undolist: after switching
1621 * to a new ipc namespace, the semaphore arrays from the old
1622 * namespace are unreachable.
1624 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1626 if ((err = unshare_thread(unshare_flags)))
1627 goto bad_unshare_out;
1628 if ((err = unshare_fs(unshare_flags, &new_fs)))
1629 goto bad_unshare_cleanup_thread;
1630 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1631 goto bad_unshare_cleanup_fs;
1632 if ((err = unshare_vm(unshare_flags, &new_mm)))
1633 goto bad_unshare_cleanup_sigh;
1634 if ((err = unshare_fd(unshare_flags, &new_fd)))
1635 goto bad_unshare_cleanup_vm;
1636 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1638 goto bad_unshare_cleanup_fd;
1640 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1643 * CLONE_SYSVSEM is equivalent to sys_exit().
1649 switch_task_namespaces(current, new_nsproxy);
1657 write_lock(&fs->lock);
1658 current->fs = new_fs;
1663 write_unlock(&fs->lock);
1668 active_mm = current->active_mm;
1669 current->mm = new_mm;
1670 current->active_mm = new_mm;
1671 activate_mm(active_mm, new_mm);
1676 fd = current->files;
1677 current->files = new_fd;
1681 task_unlock(current);
1685 put_nsproxy(new_nsproxy);
1687 bad_unshare_cleanup_fd:
1689 put_files_struct(new_fd);
1691 bad_unshare_cleanup_vm:
1695 bad_unshare_cleanup_sigh:
1697 if (atomic_dec_and_test(&new_sigh->count))
1698 kmem_cache_free(sighand_cachep, new_sigh);
1700 bad_unshare_cleanup_fs:
1702 free_fs_struct(new_fs);
1704 bad_unshare_cleanup_thread:
1710 * Helper to unshare the files of the current task.
1711 * We don't want to expose copy_files internals to
1712 * the exec layer of the kernel.
1715 int unshare_files(struct files_struct **displaced)
1717 struct task_struct *task = current;
1718 struct files_struct *copy = NULL;
1721 error = unshare_fd(CLONE_FILES, ©);
1722 if (error || !copy) {
1726 *displaced = task->files;