/* * linux/kernel/fork.c * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * 'fork.c' contains the help-routines for the 'fork' system call * (see also entry.S and others). * Fork is rather simple, once you get the hang of it, but the memory * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk); extern void exit_sem(struct task_struct *tsk); /* The idle threads do not count.. * Protected by write_lock_irq(&tasklist_lock) */ int nr_threads; int max_threads; unsigned long total_forks; /* Handle normal Linux uptimes. */ DEFINE_PER_CPU(unsigned long, process_counts) = 0; rwlock_t tasklist_lock __cacheline_aligned = RW_LOCK_UNLOCKED; /* outer */ /* * A per-CPU task cache - this relies on the fact that * the very last portion of sys_exit() is executed with * preemption turned off. */ static task_t *task_cache[NR_CPUS] __cacheline_aligned; int nr_processes(void) { int cpu; int total = 0; for (cpu = 0; cpu < NR_CPUS; cpu++) { if (cpu_online(cpu)) total += per_cpu(process_counts, cpu); } return total; } #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) static kmem_cache_t *task_struct_cachep; #endif static void free_task(struct task_struct *tsk) { /* * The task cache is effectively disabled right now. * Do we want it? The slab cache already has per-cpu * stuff, but the thread info (usually a order-1 page * allocation) doesn't. */ if (tsk != current) { free_thread_info(tsk->thread_info); free_task_struct(tsk); } else { int cpu = get_cpu(); tsk = task_cache[cpu]; if (tsk) { free_thread_info(tsk->thread_info); free_task_struct(tsk); } task_cache[cpu] = current; put_cpu(); } } void __put_task_struct(struct task_struct *tsk) { WARN_ON(!(tsk->state & (TASK_DEAD | TASK_ZOMBIE))); WARN_ON(atomic_read(&tsk->usage)); WARN_ON(tsk == current); security_task_free(tsk); free_uid(tsk->user); free_task(tsk); } void add_wait_queue(wait_queue_head_t *q, wait_queue_t * wait) { unsigned long flags; wait->flags &= ~WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&q->lock, flags); __add_wait_queue(q, wait); spin_unlock_irqrestore(&q->lock, flags); } void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t * wait) { unsigned long flags; wait->flags |= WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&q->lock, flags); __add_wait_queue_tail(q, wait); spin_unlock_irqrestore(&q->lock, flags); } void remove_wait_queue(wait_queue_head_t *q, wait_queue_t * wait) { unsigned long flags; spin_lock_irqsave(&q->lock, flags); __remove_wait_queue(q, wait); spin_unlock_irqrestore(&q->lock, flags); } void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) { unsigned long flags; __set_current_state(state); wait->flags &= ~WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) __add_wait_queue(q, wait); spin_unlock_irqrestore(&q->lock, flags); } void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) { unsigned long flags; __set_current_state(state); wait->flags |= WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) __add_wait_queue_tail(q, wait); spin_unlock_irqrestore(&q->lock, flags); } void finish_wait(wait_queue_head_t *q, wait_queue_t *wait) { unsigned long flags; __set_current_state(TASK_RUNNING); if (!list_empty(&wait->task_list)) { spin_lock_irqsave(&q->lock, flags); list_del_init(&wait->task_list); spin_unlock_irqrestore(&q->lock, flags); } } int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync) { int ret = default_wake_function(wait, mode, sync); if (ret) list_del_init(&wait->task_list); return ret; } void __init fork_init(unsigned long mempages) { #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR /* create a slab on which task_structs can be allocated */ task_struct_cachep = kmem_cache_create("task_struct", sizeof(struct task_struct),0, SLAB_MUST_HWCACHE_ALIGN, NULL, NULL); if (!task_struct_cachep) panic("fork_init(): cannot create task_struct SLAB cache"); #endif /* * The default maximum number of threads is set to a safe * value: the thread structures can take up at most half * of memory. */ max_threads = mempages / (THREAD_SIZE/PAGE_SIZE) / 8; /* * we need to allow at least 20 threads to boot a system */ if(max_threads < 20) max_threads = 20; init_task.rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; init_task.rlim[RLIMIT_NPROC].rlim_max = max_threads/2; } static struct task_struct *dup_task_struct(struct task_struct *orig) { struct task_struct *tsk; struct thread_info *ti; int cpu = get_cpu(); prepare_to_copy(orig); tsk = task_cache[cpu]; task_cache[cpu] = NULL; put_cpu(); if (!tsk) { tsk = alloc_task_struct(); if (!tsk) return NULL; ti = alloc_thread_info(tsk); if (!ti) { free_task_struct(tsk); return NULL; } } else ti = tsk->thread_info; *ti = *orig->thread_info; *tsk = *orig; tsk->thread_info = ti; ti->task = tsk; /* One for us, one for whoever does the "release_task()" (usually parent) */ atomic_set(&tsk->usage,2); return tsk; } #ifdef CONFIG_MMU static inline int dup_mmap(struct mm_struct * mm, struct mm_struct * oldmm) { struct vm_area_struct * mpnt, *tmp, **pprev; int retval; unsigned long charge = 0; down_write(&oldmm->mmap_sem); flush_cache_mm(current->mm); mm->locked_vm = 0; mm->mmap = NULL; mm->mmap_cache = NULL; mm->free_area_cache = TASK_UNMAPPED_BASE; mm->map_count = 0; mm->rss = 0; mm->cpu_vm_mask = 0; pprev = &mm->mmap; /* * Add it to the mmlist after the parent. * Doing it this way means that we can order the list, * and fork() won't mess up the ordering significantly. * Add it first so that swapoff can see any swap entries. */ spin_lock(&mmlist_lock); list_add(&mm->mmlist, ¤t->mm->mmlist); mmlist_nr++; spin_unlock(&mmlist_lock); for (mpnt = current->mm->mmap ; mpnt ; mpnt = mpnt->vm_next) { struct file *file; if(mpnt->vm_flags & VM_DONTCOPY) continue; if (mpnt->vm_flags & VM_ACCOUNT) { unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; if (security_vm_enough_memory(len)) goto fail_nomem; charge += len; } tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); if (!tmp) goto fail_nomem; *tmp = *mpnt; tmp->vm_flags &= ~VM_LOCKED; tmp->vm_mm = mm; tmp->vm_next = NULL; file = tmp->vm_file; INIT_LIST_HEAD(&tmp->shared); if (file) { struct inode *inode = file->f_dentry->d_inode; get_file(file); if (tmp->vm_flags & VM_DENYWRITE) atomic_dec(&inode->i_writecount); /* insert tmp into the share list, just after mpnt */ down(&inode->i_mapping->i_shared_sem); list_add_tail(&tmp->shared, &mpnt->shared); up(&inode->i_mapping->i_shared_sem); } /* * Link in the new vma and copy the page table entries: * link in first so that swapoff can see swap entries. */ spin_lock(&mm->page_table_lock); *pprev = tmp; pprev = &tmp->vm_next; mm->map_count++; retval = copy_page_range(mm, current->mm, tmp); spin_unlock(&mm->page_table_lock); if (tmp->vm_ops && tmp->vm_ops->open) tmp->vm_ops->open(tmp); if (retval) goto fail; } retval = 0; build_mmap_rb(mm); out: flush_tlb_mm(current->mm); up_write(&oldmm->mmap_sem); return retval; fail_nomem: retval = -ENOMEM; fail: vm_unacct_memory(charge); goto out; } static inline int mm_alloc_pgd(struct mm_struct * mm) { mm->pgd = pgd_alloc(mm); if (unlikely(!mm->pgd)) return -ENOMEM; return 0; } static inline void mm_free_pgd(struct mm_struct * mm) { pgd_free(mm->pgd); } #else #define dup_mmap(mm, oldmm) (0) #define mm_alloc_pgd(mm) (0) #define mm_free_pgd(mm) #endif /* CONFIG_MMU */ spinlock_t mmlist_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED; int mmlist_nr; #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) #include static struct mm_struct * mm_init(struct mm_struct * mm) { atomic_set(&mm->mm_users, 1); atomic_set(&mm->mm_count, 1); init_rwsem(&mm->mmap_sem); mm->core_waiters = 0; mm->page_table_lock = SPIN_LOCK_UNLOCKED; mm->ioctx_list_lock = RW_LOCK_UNLOCKED; mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm); mm->free_area_cache = TASK_UNMAPPED_BASE; if (likely(!mm_alloc_pgd(mm))) { mm->def_flags = 0; return mm; } free_mm(mm); return NULL; } /* * Allocate and initialize an mm_struct. */ struct mm_struct * mm_alloc(void) { struct mm_struct * mm; mm = allocate_mm(); if (mm) { memset(mm, 0, sizeof(*mm)); return mm_init(mm); } return NULL; } /* * Called when the last reference to the mm * is dropped: either by a lazy thread or by * mmput. Free the page directory and the mm. */ inline void __mmdrop(struct mm_struct *mm) { BUG_ON(mm == &init_mm); mm_free_pgd(mm); destroy_context(mm); free_mm(mm); } /* * Decrement the use count and release all resources for an mm. */ void mmput(struct mm_struct *mm) { if (atomic_dec_and_lock(&mm->mm_users, &mmlist_lock)) { list_del(&mm->mmlist); mmlist_nr--; spin_unlock(&mmlist_lock); exit_aio(mm); exit_mmap(mm); mmdrop(mm); } } /* Please note the differences between mmput and mm_release. * mmput is called whenever we stop holding onto a mm_struct, * error success whatever. * * mm_release is called after a mm_struct has been removed * from the current process. * * This difference is important for error handling, when we * only half set up a mm_struct for a new process and need to restore * the old one. Because we mmput the new mm_struct before * restoring the old one. . . * Eric Biederman 10 January 1998 */ void mm_release(struct task_struct *tsk, struct mm_struct *mm) { struct completion *vfork_done = tsk->vfork_done; /* Get rid of any cached register state */ deactivate_mm(tsk, mm); /* notify parent sleeping on vfork() */ if (vfork_done) { tsk->vfork_done = NULL; complete(vfork_done); } if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { u32 __user * tidptr = tsk->clear_child_tid; tsk->clear_child_tid = NULL; /* * We don't check the error code - if userspace has * not set up a proper pointer then tough luck. */ put_user(0, tidptr); sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL); } } static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) { struct mm_struct * mm, *oldmm; int retval; tsk->min_flt = tsk->maj_flt = 0; tsk->cmin_flt = tsk->cmaj_flt = 0; tsk->nswap = tsk->cnswap = 0; tsk->mm = NULL; tsk->active_mm = NULL; /* * Are we cloning a kernel thread? * * We need to steal a active VM for that.. */ oldmm = current->mm; if (!oldmm) return 0; if (clone_flags & CLONE_VM) { atomic_inc(&oldmm->mm_users); mm = oldmm; /* * There are cases where the PTL is held to ensure no * new threads start up in user mode using an mm, which * allows optimizing out ipis; the tlb_gather_mmu code * is an example. */ spin_unlock_wait(&oldmm->page_table_lock); goto good_mm; } retval = -ENOMEM; mm = allocate_mm(); if (!mm) goto fail_nomem; /* Copy the current MM stuff.. */ memcpy(mm, oldmm, sizeof(*mm)); if (!mm_init(mm)) goto fail_nomem; if (init_new_context(tsk,mm)) goto free_pt; retval = dup_mmap(mm, oldmm); if (retval) goto free_pt; good_mm: tsk->mm = mm; tsk->active_mm = mm; return 0; free_pt: mmput(mm); fail_nomem: return retval; } static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) { struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); /* We don't need to lock fs - think why ;-) */ if (fs) { atomic_set(&fs->count, 1); fs->lock = RW_LOCK_UNLOCKED; fs->umask = old->umask; read_lock(&old->lock); fs->rootmnt = mntget(old->rootmnt); fs->root = dget(old->root); fs->pwdmnt = mntget(old->pwdmnt); fs->pwd = dget(old->pwd); if (old->altroot) { fs->altrootmnt = mntget(old->altrootmnt); fs->altroot = dget(old->altroot); } else { fs->altrootmnt = NULL; fs->altroot = NULL; } read_unlock(&old->lock); } return fs; } struct fs_struct *copy_fs_struct(struct fs_struct *old) { return __copy_fs_struct(old); } static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) { if (clone_flags & CLONE_FS) { atomic_inc(¤t->fs->count); return 0; } tsk->fs = __copy_fs_struct(current->fs); if (!tsk->fs) return -ENOMEM; return 0; } static int count_open_files(struct files_struct *files, int size) { int i; /* Find the last open fd */ for (i = size/(8*sizeof(long)); i > 0; ) { if (files->open_fds->fds_bits[--i]) break; } i = (i+1) * 8 * sizeof(long); return i; } static int copy_files(unsigned long clone_flags, struct task_struct * tsk) { struct files_struct *oldf, *newf; struct file **old_fds, **new_fds; int open_files, nfds, size, i, error = 0; /* * A background process may not have any files ... */ oldf = current->files; if (!oldf) goto out; if (clone_flags & CLONE_FILES) { atomic_inc(&oldf->count); goto out; } tsk->files = NULL; error = -ENOMEM; newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); if (!newf) goto out; atomic_set(&newf->count, 1); newf->file_lock = SPIN_LOCK_UNLOCKED; newf->next_fd = 0; newf->max_fds = NR_OPEN_DEFAULT; newf->max_fdset = __FD_SETSIZE; newf->close_on_exec = &newf->close_on_exec_init; newf->open_fds = &newf->open_fds_init; newf->fd = &newf->fd_array[0]; /* We don't yet have the oldf readlock, but even if the old fdset gets grown now, we'll only copy up to "size" fds */ size = oldf->max_fdset; if (size > __FD_SETSIZE) { newf->max_fdset = 0; spin_lock(&newf->file_lock); error = expand_fdset(newf, size-1); spin_unlock(&newf->file_lock); if (error) goto out_release; } spin_lock(&oldf->file_lock); open_files = count_open_files(oldf, size); /* * Check whether we need to allocate a larger fd array. * Note: we're not a clone task, so the open count won't * change. */ nfds = NR_OPEN_DEFAULT; if (open_files > nfds) { spin_unlock(&oldf->file_lock); newf->max_fds = 0; spin_lock(&newf->file_lock); error = expand_fd_array(newf, open_files-1); spin_unlock(&newf->file_lock); if (error) goto out_release; nfds = newf->max_fds; spin_lock(&oldf->file_lock); } old_fds = oldf->fd; new_fds = newf->fd; memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8); memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8); for (i = open_files; i != 0; i--) { struct file *f = *old_fds++; if (f) get_file(f); *new_fds++ = f; } spin_unlock(&oldf->file_lock); /* compute the remainder to be cleared */ size = (newf->max_fds - open_files) * sizeof(struct file *); /* This is long word aligned thus could use a optimized version */ memset(new_fds, 0, size); if (newf->max_fdset > open_files) { int left = (newf->max_fdset-open_files)/8; int start = open_files / (8 * sizeof(unsigned long)); memset(&newf->open_fds->fds_bits[start], 0, left); memset(&newf->close_on_exec->fds_bits[start], 0, left); } tsk->files = newf; error = 0; out: return error; out_release: free_fdset (newf->close_on_exec, newf->max_fdset); free_fdset (newf->open_fds, newf->max_fdset); kmem_cache_free(files_cachep, newf); goto out; } static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) { struct sighand_struct *sig; if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { atomic_inc(¤t->sighand->count); return 0; } sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); tsk->sighand = sig; if (!sig) return -ENOMEM; spin_lock_init(&sig->siglock); atomic_set(&sig->count, 1); memcpy(sig->action, current->sighand->action, sizeof(sig->action)); return 0; } static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) { struct signal_struct *sig; if (clone_flags & CLONE_THREAD) { atomic_inc(¤t->signal->count); return 0; } sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); tsk->signal = sig; if (!sig) return -ENOMEM; atomic_set(&sig->count, 1); sig->group_exit = 0; sig->group_exit_code = 0; sig->group_exit_task = NULL; sig->group_stop_count = 0; sig->curr_target = NULL; init_sigpending(&sig->shared_pending); return 0; } static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) { unsigned long new_flags = p->flags; new_flags &= ~PF_SUPERPRIV; new_flags |= PF_FORKNOEXEC; if (!(clone_flags & CLONE_PTRACE)) p->ptrace = 0; p->flags = new_flags; } asmlinkage long sys_set_tid_address(int __user *tidptr) { current->clear_child_tid = tidptr; return current->pid; } /* * This creates a new process as a copy of the old one, * but does not actually start it yet. * * It copies the registers, and all the appropriate * parts of the process environment (as per the clone * flags). The actual kick-off is left to the caller. */ struct task_struct *copy_process(unsigned long clone_flags, unsigned long stack_start, struct pt_regs *regs, unsigned long stack_size, int __user *parent_tidptr, int __user *child_tidptr) { int retval; struct task_struct *p = NULL; if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) return ERR_PTR(-EINVAL); /* * Thread groups must share signals as well, and detached threads * can only be started up within the thread group. */ if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) return ERR_PTR(-EINVAL); if ((clone_flags & CLONE_DETACHED) && !(clone_flags & CLONE_THREAD)) return ERR_PTR(-EINVAL); retval = security_task_create(clone_flags); if (retval) goto fork_out; retval = -ENOMEM; p = dup_task_struct(current); if (!p) goto fork_out; retval = -EAGAIN; if (atomic_read(&p->user->processes) >= p->rlim[RLIMIT_NPROC].rlim_cur) { if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE)) goto bad_fork_free; } atomic_inc(&p->user->__count); atomic_inc(&p->user->processes); /* * If multiple threads are within copy_process(), then this check * triggers too late. This doesn't hurt, the check is only there * to stop root fork bombs. */ if (nr_threads >= max_threads) goto bad_fork_cleanup_count; if (!try_module_get(p->thread_info->exec_domain->module)) goto bad_fork_cleanup_count; if (p->binfmt && !try_module_get(p->binfmt->module)) goto bad_fork_cleanup_put_domain; #ifdef CONFIG_PREEMPT /* * schedule_tail drops this_rq()->lock so we compensate with a count * of 1. Also, we want to start with kernel preemption disabled. */ p->thread_info->preempt_count = 1; #endif p->did_exec = 0; p->state = TASK_UNINTERRUPTIBLE; copy_flags(clone_flags, p); if (clone_flags & CLONE_IDLETASK) p->pid = 0; else { p->pid = alloc_pidmap(); if (p->pid == -1) goto bad_fork_cleanup; } retval = -EFAULT; if (clone_flags & CLONE_PARENT_SETTID) if (put_user(p->pid, parent_tidptr)) goto bad_fork_cleanup; p->proc_dentry = NULL; INIT_LIST_HEAD(&p->run_list); INIT_LIST_HEAD(&p->children); INIT_LIST_HEAD(&p->sibling); INIT_LIST_HEAD(&p->posix_timers); init_waitqueue_head(&p->wait_chldexit); p->vfork_done = NULL; spin_lock_init(&p->alloc_lock); spin_lock_init(&p->switch_lock); spin_lock_init(&p->proc_lock); clear_tsk_thread_flag(p, TIF_SIGPENDING); init_sigpending(&p->pending); p->it_real_value = p->it_virt_value = p->it_prof_value = 0; p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0; init_timer(&p->real_timer); p->real_timer.data = (unsigned long) p; p->leader = 0; /* session leadership doesn't inherit */ p->tty_old_pgrp = 0; p->utime = p->stime = 0; p->cutime = p->cstime = 0; p->array = NULL; p->lock_depth = -1; /* -1 = no lock */ p->start_time = get_jiffies_64(); p->security = NULL; p->io_context = NULL; retval = -ENOMEM; if ((retval = security_task_alloc(p))) goto bad_fork_cleanup; /* copy all the process information */ if ((retval = copy_semundo(clone_flags, p))) goto bad_fork_cleanup_security; if ((retval = copy_files(clone_flags, p))) goto bad_fork_cleanup_semundo; if ((retval = copy_fs(clone_flags, p))) goto bad_fork_cleanup_files; if ((retval = copy_sighand(clone_flags, p))) goto bad_fork_cleanup_fs; if ((retval = copy_signal(clone_flags, p))) goto bad_fork_cleanup_sighand; if ((retval = copy_mm(clone_flags, p))) goto bad_fork_cleanup_signal; if ((retval = copy_namespace(clone_flags, p))) goto bad_fork_cleanup_mm; retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); if (retval) goto bad_fork_cleanup_namespace; p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; /* * Clear TID on mm_release()? */ p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; /* * Syscall tracing should be turned off in the child regardless * of CLONE_PTRACE. */ clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); /* Our parent execution domain becomes current domain These must match for thread signalling to apply */ p->parent_exec_id = p->self_exec_id; /* ok, now we should be set up.. */ if (clone_flags & CLONE_DETACHED) p->exit_signal = -1; else p->exit_signal = clone_flags & CSIGNAL; p->pdeath_signal = 0; /* * Share the timeslice between parent and child, thus the * total amount of pending timeslices in the system doesn't change, * resulting in more scheduling fairness. */ local_irq_disable(); p->time_slice = (current->time_slice + 1) >> 1; /* * The remainder of the first timeslice might be recovered by * the parent if the child exits early enough. */ p->first_time_slice = 1; current->time_slice >>= 1; p->last_run = jiffies; if (!current->time_slice) { /* * This case is rare, it happens when the parent has only * a single jiffy left from its timeslice. Taking the * runqueue lock is not a problem. */ current->time_slice = 1; preempt_disable(); scheduler_tick(0, 0); local_irq_enable(); preempt_enable(); } else local_irq_enable(); /* * Ok, add it to the run-queues and make it * visible to the rest of the system. * * Let it rip! */ p->tgid = p->pid; p->group_leader = p; INIT_LIST_HEAD(&p->ptrace_children); INIT_LIST_HEAD(&p->ptrace_list); /* Need tasklist lock for parent etc handling! */ write_lock_irq(&tasklist_lock); /* * Check for pending SIGKILL! The new thread should not be allowed * to slip out of an OOM kill. (or normal SIGKILL.) */ if (sigismember(¤t->pending.signal, SIGKILL)) { write_unlock_irq(&tasklist_lock); retval = -EINTR; goto bad_fork_cleanup_namespace; } /* CLONE_PARENT re-uses the old parent */ if (clone_flags & CLONE_PARENT) p->real_parent = current->real_parent; else p->real_parent = current; p->parent = p->real_parent; if (clone_flags & CLONE_THREAD) { spin_lock(¤t->sighand->siglock); /* * Important: if an exit-all has been started then * do not create this new thread - the whole thread * group is supposed to exit anyway. */ if (current->signal->group_exit) { spin_unlock(¤t->sighand->siglock); write_unlock_irq(&tasklist_lock); goto bad_fork_cleanup_namespace; } p->tgid = current->tgid; p->group_leader = current->group_leader; if (current->signal->group_stop_count > 0) { /* * There is an all-stop in progress for the group. * We ourselves will stop as soon as we check signals. * Make the new thread part of that group stop too. */ current->signal->group_stop_count++; set_tsk_thread_flag(p, TIF_SIGPENDING); } spin_unlock(¤t->sighand->siglock); } SET_LINKS(p); if (p->ptrace & PT_PTRACED) __ptrace_link(p, current->parent); attach_pid(p, PIDTYPE_PID, p->pid); if (thread_group_leader(p)) { attach_pid(p, PIDTYPE_TGID, p->tgid); attach_pid(p, PIDTYPE_PGID, p->pgrp); attach_pid(p, PIDTYPE_SID, p->session); if (p->pid) __get_cpu_var(process_counts)++; } else link_pid(p, p->pids + PIDTYPE_TGID, &p->group_leader->pids[PIDTYPE_TGID].pid); nr_threads++; write_unlock_irq(&tasklist_lock); retval = 0; fork_out: if (retval) return ERR_PTR(retval); return p; bad_fork_cleanup_namespace: exit_namespace(p); bad_fork_cleanup_mm: exit_mm(p); bad_fork_cleanup_signal: exit_signal(p); bad_fork_cleanup_sighand: exit_sighand(p); bad_fork_cleanup_fs: exit_fs(p); /* blocking */ bad_fork_cleanup_files: exit_files(p); /* blocking */ bad_fork_cleanup_semundo: exit_sem(p); bad_fork_cleanup_security: security_task_free(p); bad_fork_cleanup: if (p->pid > 0) free_pidmap(p->pid); if (p->binfmt) module_put(p->binfmt->module); bad_fork_cleanup_put_domain: module_put(p->thread_info->exec_domain->module); bad_fork_cleanup_count: atomic_dec(&p->user->processes); free_uid(p->user); bad_fork_free: free_task(p); goto fork_out; } static inline int fork_traceflag (unsigned clone_flags) { if (clone_flags & (CLONE_UNTRACED | CLONE_IDLETASK)) return 0; else if (clone_flags & CLONE_VFORK) { if (current->ptrace & PT_TRACE_VFORK) return PTRACE_EVENT_VFORK; } else if ((clone_flags & CSIGNAL) != SIGCHLD) { if (current->ptrace & PT_TRACE_CLONE) return PTRACE_EVENT_CLONE; } else if (current->ptrace & PT_TRACE_FORK) return PTRACE_EVENT_FORK; return 0; } /* * Ok, this is the main fork-routine. * * It copies the process, and if successful kick-starts * it and waits for it to finish using the VM if required. */ long do_fork(unsigned long clone_flags, unsigned long stack_start, struct pt_regs *regs, unsigned long stack_size, int __user *parent_tidptr, int __user *child_tidptr) { struct task_struct *p; int trace = 0; long pid; if (unlikely(current->ptrace)) { trace = fork_traceflag (clone_flags); if (trace) clone_flags |= CLONE_PTRACE; } p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr); /* * Do this prior waking up the new thread - the thread pointer * might get invalid after that point, if the thread exits quickly. */ pid = IS_ERR(p) ? PTR_ERR(p) : p->pid; if (!IS_ERR(p)) { struct completion vfork; if (clone_flags & CLONE_VFORK) { p->vfork_done = &vfork; init_completion(&vfork); } if (p->ptrace & PT_PTRACED) { /* * We'll start up with an immediate SIGSTOP. */ sigaddset(&p->pending.signal, SIGSTOP); set_tsk_thread_flag(p, TIF_SIGPENDING); } wake_up_forked_process(p); /* do this last */ ++total_forks; if (unlikely (trace)) { current->ptrace_message = pid; ptrace_notify ((trace << 8) | SIGTRAP); } if (clone_flags & CLONE_VFORK) { wait_for_completion(&vfork); if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); } else /* * Let the child process run first, to avoid most of the * COW overhead when the child exec()s afterwards. */ set_need_resched(); } return pid; } /* SLAB cache for signal_struct structures (tsk->signal) */ kmem_cache_t *signal_cachep; /* SLAB cache for sighand_struct structures (tsk->sighand) */ kmem_cache_t *sighand_cachep; /* SLAB cache for files_struct structures (tsk->files) */ kmem_cache_t *files_cachep; /* SLAB cache for fs_struct structures (tsk->fs) */ kmem_cache_t *fs_cachep; /* SLAB cache for vm_area_struct structures */ kmem_cache_t *vm_area_cachep; /* SLAB cache for mm_struct structures (tsk->mm) */ kmem_cache_t *mm_cachep; void __init proc_caches_init(void) { sighand_cachep = kmem_cache_create("sighand_cache", sizeof(struct sighand_struct), 0, SLAB_HWCACHE_ALIGN, NULL, NULL); if (!sighand_cachep) panic("Cannot create sighand SLAB cache"); signal_cachep = kmem_cache_create("signal_cache", sizeof(struct signal_struct), 0, SLAB_HWCACHE_ALIGN, NULL, NULL); if (!signal_cachep) panic("Cannot create signal SLAB cache"); files_cachep = kmem_cache_create("files_cache", sizeof(struct files_struct), 0, SLAB_HWCACHE_ALIGN, NULL, NULL); if (!files_cachep) panic("Cannot create files SLAB cache"); fs_cachep = kmem_cache_create("fs_cache", sizeof(struct fs_struct), 0, SLAB_HWCACHE_ALIGN, NULL, NULL); if (!fs_cachep) panic("Cannot create fs_struct SLAB cache"); vm_area_cachep = kmem_cache_create("vm_area_struct", sizeof(struct vm_area_struct), 0, 0, NULL, NULL); if(!vm_area_cachep) panic("vma_init: Cannot alloc vm_area_struct SLAB cache"); mm_cachep = kmem_cache_create("mm_struct", sizeof(struct mm_struct), 0, SLAB_HWCACHE_ALIGN, NULL, NULL); if(!mm_cachep) panic("vma_init: Cannot alloc mm_struct SLAB cache"); }