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fork.c
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/*
* 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 <linux/slab.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/mempolicy.h>
#include <linux/sem.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/iocontext.h>
#include <linux/key.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
#include <linux/mmu_notifier.h>
#include <linux/fs.h>
#include <linux/nsproxy.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/cgroup.h>
#include <linux/security.h>
#include <linux/hugetlb.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
#include <linux/compat.h>
#include <linux/kthread.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/rcupdate.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/memcontrol.h>
#include <linux/ftrace.h>
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/ksm.h>
#include <linux/acct.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/freezer.h>
#include <linux/delayacct.h>
#include <linux/taskstats_kern.h>
#include <linux/random.h>
#include <linux/tty.h>
#include <linux/blkdev.h>
#include <linux/fs_struct.h>
#include <linux/magic.h>
#include <linux/perf_event.h>
#include <linux/posix-timers.h>
#include <linux/user-return-notifier.h>
#include <linux/oom.h>
#include <linux/khugepaged.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <trace/events/sched.h>
/*
* Protected counters by write_lock_irq(&tasklist_lock)
*/
unsigned long total_forks; /* Handle normal Linux uptimes. */
int nr_threads; /* The idle threads do not count.. */
int max_threads; /* tunable limit on nr_threads */
DEFINE_PER_CPU(unsigned long, process_counts) = 0;
__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
#ifdef CONFIG_PROVE_RCU
int lockdep_tasklist_lock_is_held(void)
{
return lockdep_is_held(&tasklist_lock);
}
EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
#endif /* #ifdef CONFIG_PROVE_RCU */
int nr_processes(void)
{
int cpu;
int total = 0;
for_each_possible_cpu(cpu)
total += per_cpu(process_counts, cpu);
return total;
}
#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
# define alloc_task_struct_node(node) \
kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
# define free_task_struct(tsk) \
kmem_cache_free(task_struct_cachep, (tsk))
static struct kmem_cache *task_struct_cachep;
#endif
#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
int node)
{
#ifdef CONFIG_DEBUG_STACK_USAGE
gfp_t mask = GFP_KERNEL | __GFP_ZERO;
#else
gfp_t mask = GFP_KERNEL;
#endif
struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
return page ? page_address(page) : NULL;
}
static inline void free_thread_info(struct thread_info *ti)
{
free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
#endif
/* SLAB cache for signal_struct structures (tsk->signal) */
static struct kmem_cache *signal_cachep;
/* SLAB cache for sighand_struct structures (tsk->sighand) */
struct kmem_cache *sighand_cachep;
/* SLAB cache for files_struct structures (tsk->files) */
struct kmem_cache *files_cachep;
/* SLAB cache for fs_struct structures (tsk->fs) */
struct kmem_cache *fs_cachep;
/* SLAB cache for vm_area_struct structures */
struct kmem_cache *vm_area_cachep;
/* SLAB cache for mm_struct structures (tsk->mm) */
static struct kmem_cache *mm_cachep;
/* Notifier list called when a task struct is freed */
static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
static void account_kernel_stack(struct thread_info *ti, int account)
{
struct zone *zone = page_zone(virt_to_page(ti));
mod_zone_page_state(zone, NR_KERNEL_STACK, account);
}
void free_task(struct task_struct *tsk)
{
prop_local_destroy_single(&tsk->dirties);
account_kernel_stack(tsk->stack, -1);
free_thread_info(tsk->stack);
rt_mutex_debug_task_free(tsk);
ftrace_graph_exit_task(tsk);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
static inline void free_signal_struct(struct signal_struct *sig)
{
taskstats_tgid_free(sig);
sched_autogroup_exit(sig);
kmem_cache_free(signal_cachep, sig);
}
static inline void put_signal_struct(struct signal_struct *sig)
{
if (atomic_dec_and_test(&sig->sigcnt))
free_signal_struct(sig);
}
int task_free_register(struct notifier_block *n)
{
return atomic_notifier_chain_register(&task_free_notifier, n);
}
EXPORT_SYMBOL(task_free_register);
int task_free_unregister(struct notifier_block *n)
{
return atomic_notifier_chain_unregister(&task_free_notifier, n);
}
EXPORT_SYMBOL(task_free_unregister);
void __put_task_struct(struct task_struct *tsk)
{
WARN_ON(!tsk->exit_state);
WARN_ON(atomic_read(&tsk->usage));
WARN_ON(tsk == current);
exit_creds(tsk);
delayacct_tsk_free(tsk);
put_signal_struct(tsk->signal);
atomic_notifier_call_chain(&task_free_notifier, 0, tsk);
if (!profile_handoff_task(tsk))
free_task(tsk);
}
EXPORT_SYMBOL_GPL(__put_task_struct);
/*
* macro override instead of weak attribute alias, to workaround
* gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
*/
#ifndef arch_task_cache_init
#define arch_task_cache_init()
#endif
void __init fork_init(unsigned long mempages)
{
#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
#endif
/* create a slab on which task_structs can be allocated */
task_struct_cachep =
kmem_cache_create("task_struct", sizeof(struct task_struct),
ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
#endif
/* do the arch specific task caches init */
arch_task_cache_init();
/*
* 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 / (8 * THREAD_SIZE / PAGE_SIZE);
/*
* we need to allow at least 20 threads to boot a system
*/
if (max_threads < 20)
max_threads = 20;
init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
init_task.signal->rlim[RLIMIT_SIGPENDING] =
init_task.signal->rlim[RLIMIT_NPROC];
}
int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
struct task_struct *src)
{
*dst = *src;
return 0;
}
static struct task_struct *dup_task_struct(struct task_struct *orig)
{
struct task_struct *tsk;
struct thread_info *ti;
unsigned long *stackend;
int node = tsk_fork_get_node(orig);
int err;
prepare_to_copy(orig);
tsk = alloc_task_struct_node(node);
if (!tsk)
return NULL;
ti = alloc_thread_info_node(tsk, node);
if (!ti) {
free_task_struct(tsk);
return NULL;
}
err = arch_dup_task_struct(tsk, orig);
if (err)
goto out;
tsk->stack = ti;
err = prop_local_init_single(&tsk->dirties);
if (err)
goto out;
setup_thread_stack(tsk, orig);
clear_user_return_notifier(tsk);
clear_tsk_need_resched(tsk);
stackend = end_of_stack(tsk);
*stackend = STACK_END_MAGIC; /* for overflow detection */
#ifdef CONFIG_CC_STACKPROTECTOR
tsk->stack_canary = get_random_int();
#endif
/*
* One for us, one for whoever does the "release_task()" (usually
* parent)
*/
atomic_set(&tsk->usage, 2);
#ifdef CONFIG_BLK_DEV_IO_TRACE
tsk->btrace_seq = 0;
#endif
tsk->splice_pipe = NULL;
account_kernel_stack(ti, 1);
return tsk;
out:
free_thread_info(ti);
free_task_struct(tsk);
return NULL;
}
#ifdef CONFIG_MMU
static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
{
struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
struct rb_node **rb_link, *rb_parent;
int retval;
unsigned long charge;
struct mempolicy *pol;
down_write(&oldmm->mmap_sem);
flush_cache_dup_mm(oldmm);
/*
* Not linked in yet - no deadlock potential:
*/
down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
mm->locked_vm = 0;
mm->mmap = NULL;
mm->mmap_cache = NULL;
mm->free_area_cache = oldmm->mmap_base;
mm->cached_hole_size = ~0UL;
mm->map_count = 0;
cpumask_clear(mm_cpumask(mm));
mm->mm_rb = RB_ROOT;
rb_link = &mm->mm_rb.rb_node;
rb_parent = NULL;
pprev = &mm->mmap;
retval = ksm_fork(mm, oldmm);
if (retval)
goto out;
retval = khugepaged_fork(mm, oldmm);
if (retval)
goto out;
prev = NULL;
for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
struct file *file;
if (mpnt->vm_flags & VM_DONTCOPY) {
long pages = vma_pages(mpnt);
mm->total_vm -= pages;
vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
-pages);
continue;
}
charge = 0;
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, GFP_KERNEL);
if (!tmp)
goto fail_nomem;
*tmp = *mpnt;
INIT_LIST_HEAD(&tmp->anon_vma_chain);
pol = mpol_dup(vma_policy(mpnt));
retval = PTR_ERR(pol);
if (IS_ERR(pol))
goto fail_nomem_policy;
vma_set_policy(tmp, pol);
tmp->vm_mm = mm;
if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
tmp->vm_flags &= ~VM_LOCKED;
tmp->vm_next = tmp->vm_prev = NULL;
file = tmp->vm_file;
if (file) {
struct inode *inode = file->f_path.dentry->d_inode;
struct address_space *mapping = file->f_mapping;
get_file(file);
if (tmp->vm_flags & VM_DENYWRITE)
atomic_dec(&inode->i_writecount);
mutex_lock(&mapping->i_mmap_mutex);
if (tmp->vm_flags & VM_SHARED)
mapping->i_mmap_writable++;
flush_dcache_mmap_lock(mapping);
/* insert tmp into the share list, just after mpnt */
vma_prio_tree_add(tmp, mpnt);
flush_dcache_mmap_unlock(mapping);
mutex_unlock(&mapping->i_mmap_mutex);
}
/*
* Clear hugetlb-related page reserves for children. This only
* affects MAP_PRIVATE mappings. Faults generated by the child
* are not guaranteed to succeed, even if read-only
*/
if (is_vm_hugetlb_page(tmp))
reset_vma_resv_huge_pages(tmp);
/*
* Link in the new vma and copy the page table entries.
*/
*pprev = tmp;
pprev = &tmp->vm_next;
tmp->vm_prev = prev;
prev = tmp;
__vma_link_rb(mm, tmp, rb_link, rb_parent);
rb_link = &tmp->vm_rb.rb_right;
rb_parent = &tmp->vm_rb;
mm->map_count++;
retval = copy_page_range(mm, oldmm, mpnt);
if (tmp->vm_ops && tmp->vm_ops->open)
tmp->vm_ops->open(tmp);
if (retval)
goto out;
}
/* a new mm has just been created */
arch_dup_mmap(oldmm, mm);
retval = 0;
out:
up_write(&mm->mmap_sem);
flush_tlb_mm(oldmm);
up_write(&oldmm->mmap_sem);
return retval;
fail_nomem_anon_vma_fork:
mpol_put(pol);
fail_nomem_policy:
kmem_cache_free(vm_area_cachep, tmp);
fail_nomem:
retval = -ENOMEM;
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, mm->pgd);
}
#else
#define dup_mmap(mm, oldmm) (0)
#define mm_alloc_pgd(mm) (0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */
__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
static int __init coredump_filter_setup(char *s)
{
default_dump_filter =
(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
MMF_DUMP_FILTER_MASK;
return 1;
}
__setup("coredump_filter=", coredump_filter_setup);
#include <linux/init_task.h>
static void mm_init_aio(struct mm_struct *mm)
{
#ifdef CONFIG_AIO
spin_lock_init(&mm->ioctx_lock);
INIT_HLIST_HEAD(&mm->ioctx_list);
#endif
}
static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
{
atomic_set(&mm->mm_users, 1);
atomic_set(&mm->mm_count, 1);
init_rwsem(&mm->mmap_sem);
INIT_LIST_HEAD(&mm->mmlist);
mm->flags = (current->mm) ?
(current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
mm->core_state = NULL;
mm->nr_ptes = 0;
memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
spin_lock_init(&mm->page_table_lock);
mm->free_area_cache = TASK_UNMAPPED_BASE;
mm->cached_hole_size = ~0UL;
mm_init_aio(mm);
mm_init_owner(mm, p);
atomic_set(&mm->oom_disable_count, 0);
if (likely(!mm_alloc_pgd(mm))) {
mm->def_flags = 0;
mmu_notifier_mm_init(mm);
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)
return NULL;
memset(mm, 0, sizeof(*mm));
mm_init_cpumask(mm);
return mm_init(mm, current);
}
/*
* 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.
*/
void __mmdrop(struct mm_struct *mm)
{
BUG_ON(mm == &init_mm);
mm_free_pgd(mm);
destroy_context(mm);
mmu_notifier_mm_destroy(mm);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
VM_BUG_ON(mm->pmd_huge_pte);
#endif
free_mm(mm);
}
EXPORT_SYMBOL_GPL(__mmdrop);
/*
* Decrement the use count and release all resources for an mm.
*/
void mmput(struct mm_struct *mm)
{
might_sleep();
if (atomic_dec_and_test(&mm->mm_users)) {
exit_aio(mm);
ksm_exit(mm);
khugepaged_exit(mm); /* must run before exit_mmap */
exit_mmap(mm);
set_mm_exe_file(mm, NULL);
if (!list_empty(&mm->mmlist)) {
spin_lock(&mmlist_lock);
list_del(&mm->mmlist);
spin_unlock(&mmlist_lock);
}
put_swap_token(mm);
if (mm->binfmt)
module_put(mm->binfmt->module);
mmdrop(mm);
}
}
EXPORT_SYMBOL_GPL(mmput);
/*
* We added or removed a vma mapping the executable. The vmas are only mapped
* during exec and are not mapped with the mmap system call.
* Callers must hold down_write() on the mm's mmap_sem for these
*/
void added_exe_file_vma(struct mm_struct *mm)
{
mm->num_exe_file_vmas++;
}
void removed_exe_file_vma(struct mm_struct *mm)
{
mm->num_exe_file_vmas--;
if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
fput(mm->exe_file);
mm->exe_file = NULL;
}
}
void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
{
if (new_exe_file)
get_file(new_exe_file);
if (mm->exe_file)
fput(mm->exe_file);
mm->exe_file = new_exe_file;
mm->num_exe_file_vmas = 0;
}
struct file *get_mm_exe_file(struct mm_struct *mm)
{
struct file *exe_file;
/* We need mmap_sem to protect against races with removal of
* VM_EXECUTABLE vmas */
down_read(&mm->mmap_sem);
exe_file = mm->exe_file;
if (exe_file)
get_file(exe_file);
up_read(&mm->mmap_sem);
return exe_file;
}
static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
{
/* It's safe to write the exe_file pointer without exe_file_lock because
* this is called during fork when the task is not yet in /proc */
newmm->exe_file = get_mm_exe_file(oldmm);
}
/**
* get_task_mm - acquire a reference to the task's mm
*
* Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
* this kernel workthread has transiently adopted a user mm with use_mm,
* to do its AIO) is not set and if so returns a reference to it, after
* bumping up the use count. User must release the mm via mmput()
* after use. Typically used by /proc and ptrace.
*/
struct mm_struct *get_task_mm(struct task_struct *task)
{
struct mm_struct *mm;
task_lock(task);
mm = task->mm;
if (mm) {
if (task->flags & PF_KTHREAD)
mm = NULL;
else
atomic_inc(&mm->mm_users);
}
task_unlock(task);
return mm;
}
EXPORT_SYMBOL_GPL(get_task_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 futexes when releasing the mm */
#ifdef CONFIG_FUTEX
if (unlikely(tsk->robust_list)) {
exit_robust_list(tsk);
tsk->robust_list = NULL;
}
#ifdef CONFIG_COMPAT
if (unlikely(tsk->compat_robust_list)) {
compat_exit_robust_list(tsk);
tsk->compat_robust_list = NULL;
}
#endif
if (unlikely(!list_empty(&tsk->pi_state_list)))
exit_pi_state_list(tsk);
#endif
/* 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 we're exiting normally, clear a user-space tid field if
* requested. We leave this alone when dying by signal, to leave
* the value intact in a core dump, and to save the unnecessary
* trouble otherwise. Userland only wants this done for a sys_exit.
*/
if (tsk->clear_child_tid) {
if (!(tsk->flags & PF_SIGNALED) &&
atomic_read(&mm->mm_users) > 1) {
/*
* We don't check the error code - if userspace has
* not set up a proper pointer then tough luck.
*/
put_user(0, tsk->clear_child_tid);
sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1, NULL, NULL, 0);
}
tsk->clear_child_tid = NULL;
}
}
/*
* Allocate a new mm structure and copy contents from the
* mm structure of the passed in task structure.
*/
struct mm_struct *dup_mm(struct task_struct *tsk)
{
struct mm_struct *mm, *oldmm = current->mm;
int err;
if (!oldmm)
return NULL;
mm = allocate_mm();
if (!mm)
goto fail_nomem;
memcpy(mm, oldmm, sizeof(*mm));
mm_init_cpumask(mm);
/* Initializing for Swap token stuff */
mm->token_priority = 0;
mm->last_interval = 0;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
mm->pmd_huge_pte = NULL;
#endif
if (!mm_init(mm, tsk))
goto fail_nomem;
if (init_new_context(tsk, mm))
goto fail_nocontext;
dup_mm_exe_file(oldmm, mm);
err = dup_mmap(mm, oldmm);
if (err)
goto free_pt;
mm->hiwater_rss = get_mm_rss(mm);
mm->hiwater_vm = mm->total_vm;
if (mm->binfmt && !try_module_get(mm->binfmt->module))
goto free_pt;
return mm;
free_pt:
/* don't put binfmt in mmput, we haven't got module yet */
mm->binfmt = NULL;
mmput(mm);
fail_nomem:
return NULL;
fail_nocontext:
/*
* If init_new_context() failed, we cannot use mmput() to free the mm
* because it calls destroy_context()
*/
mm_free_pgd(mm);
free_mm(mm);
return 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->nvcsw = tsk->nivcsw = 0;
#ifdef CONFIG_DETECT_HUNG_TASK
tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
#endif
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;
goto good_mm;
}
retval = -ENOMEM;
mm = dup_mm(tsk);
if (!mm)
goto fail_nomem;
good_mm:
/* Initializing for Swap token stuff */
mm->token_priority = 0;
mm->last_interval = 0;
if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
atomic_inc(&mm->oom_disable_count);
tsk->mm = mm;
tsk->active_mm = mm;
return 0;
fail_nomem:
return retval;
}
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
{
struct fs_struct *fs = current->fs;
if (clone_flags & CLONE_FS) {
/* tsk->fs is already what we want */
spin_lock(&fs->lock);
if (fs->in_exec) {
spin_unlock(&fs->lock);
return -EAGAIN;
}
fs->users++;
spin_unlock(&fs->lock);
return 0;
}
tsk->fs = copy_fs_struct(fs);
if (!tsk->fs)
return -ENOMEM;
return 0;
}
static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
{
struct files_struct *oldf, *newf;
int 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;
}
newf = dup_fd(oldf, &error);
if (!newf)
goto out;
tsk->files = newf;
error = 0;
out:
return error;
}
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
{
#ifdef CONFIG_BLOCK
struct io_context *ioc = current->io_context;
if (!ioc)
return 0;
/*
* Share io context with parent, if CLONE_IO is set
*/
if (clone_flags & CLONE_IO) {
tsk->io_context = ioc_task_link(ioc);
if (unlikely(!tsk->io_context))
return -ENOMEM;
} else if (ioprio_valid(ioc->ioprio)) {
tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
if (unlikely(!tsk->io_context))
return -ENOMEM;
tsk->io_context->ioprio = ioc->ioprio;
}
#endif
return 0;
}
static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
{
struct sighand_struct *sig;
if (clone_flags & CLONE_SIGHAND) {
atomic_inc(¤t->sighand->count);
return 0;
}
sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
rcu_assign_pointer(tsk->sighand, sig);
if (!sig)
return -ENOMEM;
atomic_set(&sig->count, 1);
memcpy(sig->action, current->sighand->action, sizeof(sig->action));
return 0;
}
void __cleanup_sighand(struct sighand_struct *sighand)
{
if (atomic_dec_and_test(&sighand->count))
kmem_cache_free(sighand_cachep, sighand);
}
/*
* Initialize POSIX timer handling for a thread group.
*/
static void posix_cpu_timers_init_group(struct signal_struct *sig)
{
unsigned long cpu_limit;
/* Thread group counters. */
thread_group_cputime_init(sig);
cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
if (cpu_limit != RLIM_INFINITY) {
sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
sig->cputimer.running = 1;
}
/* The timer lists. */
INIT_LIST_HEAD(&sig->cpu_timers[0]);
INIT_LIST_HEAD(&sig->cpu_timers[1]);
INIT_LIST_HEAD(&sig->cpu_timers[2]);
}
static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
{
struct signal_struct *sig;
if (clone_flags & CLONE_THREAD)
return 0;
sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
tsk->signal = sig;
if (!sig)
return -ENOMEM;
sig->nr_threads = 1;
atomic_set(&sig->live, 1);
atomic_set(&sig->sigcnt, 1);
init_waitqueue_head(&sig->wait_chldexit);
if (clone_flags & CLONE_NEWPID)
sig->flags |= SIGNAL_UNKILLABLE;
sig->curr_target = tsk;
init_sigpending(&sig->shared_pending);
INIT_LIST_HEAD(&sig->posix_timers);
hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
sig->real_timer.function = it_real_fn;
task_lock(current->group_leader);
memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
task_unlock(current->group_leader);
posix_cpu_timers_init_group(sig);
tty_audit_fork(sig);
sched_autogroup_fork(sig);
#ifdef CONFIG_CGROUPS
init_rwsem(&sig->threadgroup_fork_lock);
#endif