proc: turn signal_struct->count into "int nr_threads"
[linux-2.6.git] / kernel / fork.c
index 29b532e..d32410b 100644 (file)
@@ -49,6 +49,7 @@
 #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>
@@ -61,7 +62,9 @@
 #include <linux/blkdev.h>
 #include <linux/fs_struct.h>
 #include <linux/magic.h>
-#include <linux/perf_counter.h>
+#include <linux/perf_event.h>
+#include <linux/posix-timers.h>
+#include <linux/user-return-notifier.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -84,12 +87,20 @@ 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_online_cpu(cpu)
+       for_each_possible_cpu(cpu)
                total += per_cpu(process_counts, cpu);
 
        return total;
@@ -136,9 +147,17 @@ struct kmem_cache *vm_area_cachep;
 /* SLAB cache for mm_struct structures (tsk->mm) */
 static struct kmem_cache *mm_cachep;
 
+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);
@@ -146,15 +165,27 @@ void free_task(struct task_struct *tsk)
 }
 EXPORT_SYMBOL(free_task);
 
+static inline void free_signal_struct(struct signal_struct *sig)
+{
+       taskstats_tgid_free(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);
+}
+
 void __put_task_struct(struct task_struct *tsk)
 {
        WARN_ON(!tsk->exit_state);
        WARN_ON(atomic_read(&tsk->usage));
        WARN_ON(tsk == current);
 
-       put_cred(tsk->real_cred);
-       put_cred(tsk->cred);
+       exit_creds(tsk);
        delayacct_tsk_free(tsk);
+       put_signal_struct(tsk->signal);
 
        if (!profile_handoff_task(tsk))
                free_task(tsk);
@@ -240,6 +271,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
                goto out;
 
        setup_thread_stack(tsk, orig);
+       clear_user_return_notifier(tsk);
        stackend = end_of_stack(tsk);
        *stackend = STACK_END_MAGIC;    /* for overflow detection */
 
@@ -254,6 +286,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
        tsk->btrace_seq = 0;
 #endif
        tsk->splice_pipe = NULL;
+
+       account_kernel_stack(ti, 1);
+
        return tsk;
 
 out:
@@ -289,6 +324,9 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
        rb_link = &mm->mm_rb.rb_node;
        rb_parent = NULL;
        pprev = &mm->mmap;
+       retval = ksm_fork(mm, oldmm);
+       if (retval)
+               goto out;
 
        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
                struct file *file;
@@ -311,15 +349,17 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
                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);
+               if (anon_vma_fork(tmp, mpnt))
+                       goto fail_nomem_anon_vma_fork;
                tmp->vm_flags &= ~VM_LOCKED;
                tmp->vm_mm = mm;
                tmp->vm_next = NULL;
-               anon_vma_link(tmp);
                file = tmp->vm_file;
                if (file) {
                        struct inode *inode = file->f_path.dentry->d_inode;
@@ -374,6 +414,8 @@ out:
        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:
@@ -419,23 +461,29 @@ __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 : default_dump_filter;
-       mm->oom_adj = (current->mm) ? current->mm->oom_adj : 0;
+       mm->flags = (current->mm) ?
+               (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
        mm->core_state = NULL;
        mm->nr_ptes = 0;
-       set_mm_counter(mm, file_rss, 0);
-       set_mm_counter(mm, anon_rss, 0);
+       memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
        spin_lock_init(&mm->page_table_lock);
-       spin_lock_init(&mm->ioctx_lock);
-       INIT_HLIST_HEAD(&mm->ioctx_list);
        mm->free_area_cache = TASK_UNMAPPED_BASE;
        mm->cached_hole_size = ~0UL;
+       mm_init_aio(mm);
        mm_init_owner(mm, p);
 
        if (likely(!mm_alloc_pgd(mm))) {
@@ -487,6 +535,7 @@ void mmput(struct mm_struct *mm)
 
        if (atomic_dec_and_test(&mm->mm_users)) {
                exit_aio(mm);
+               ksm_exit(mm);
                exit_mmap(mm);
                set_mm_exe_file(mm, NULL);
                if (!list_empty(&mm->mmlist)) {
@@ -495,6 +544,8 @@ void mmput(struct mm_struct *mm)
                        spin_unlock(&mmlist_lock);
                }
                put_swap_token(mm);
+               if (mm->binfmt)
+                       module_put(mm->binfmt->module);
                mmdrop(mm);
        }
 }
@@ -545,12 +596,18 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 
        /* Get rid of any futexes when releasing the mm */
 #ifdef CONFIG_FUTEX
-       if (unlikely(tsk->robust_list))
+       if (unlikely(tsk->robust_list)) {
                exit_robust_list(tsk);
+               tsk->robust_list = NULL;
+       }
 #ifdef CONFIG_COMPAT
-       if (unlikely(tsk->compat_robust_list))
+       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 */
@@ -568,18 +625,18 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
         * 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
-           && !(tsk->flags & PF_SIGNALED)
-           && atomic_read(&mm->mm_users) > 1) {
-               u32 __user * tidptr = tsk->clear_child_tid;
+       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;
-
-               /*
-                * 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, 0);
        }
 }
 
@@ -620,9 +677,14 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
        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:
@@ -786,23 +848,14 @@ void __cleanup_sighand(struct sighand_struct *sighand)
  */
 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 {
+       unsigned long cpu_limit;
+
        /* Thread group counters. */
        thread_group_cputime_init(sig);
 
-       /* Expiration times and increments. */
-       sig->it_virt_expires = cputime_zero;
-       sig->it_virt_incr = cputime_zero;
-       sig->it_prof_expires = cputime_zero;
-       sig->it_prof_incr = cputime_zero;
-
-       /* Cached expiration times. */
-       sig->cputime_expires.prof_exp = cputime_zero;
-       sig->cputime_expires.virt_exp = cputime_zero;
-       sig->cputime_expires.sched_exp = 0;
-
-       if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
-               sig->cputime_expires.prof_exp =
-                       secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
+       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;
        }
 
@@ -816,76 +869,38 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 {
        struct signal_struct *sig;
 
-       if (clone_flags & CLONE_THREAD) {
-               atomic_inc(&current->signal->count);
-               atomic_inc(&current->signal->live);
+       if (clone_flags & CLONE_THREAD)
                return 0;
-       }
 
-       sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
+       sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
        tsk->signal = sig;
        if (!sig)
                return -ENOMEM;
 
-       atomic_set(&sig->count, 1);
+       sig->nr_threads = 1;
        atomic_set(&sig->live, 1);
+       atomic_set(&sig->sigcnt, 1);
        init_waitqueue_head(&sig->wait_chldexit);
-       sig->flags = 0;
        if (clone_flags & CLONE_NEWPID)
                sig->flags |= SIGNAL_UNKILLABLE;
-       sig->group_exit_code = 0;
-       sig->group_exit_task = NULL;
-       sig->group_stop_count = 0;
        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->it_real_incr.tv64 = 0;
        sig->real_timer.function = it_real_fn;
 
-       sig->leader = 0;        /* session leadership doesn't inherit */
-       sig->tty_old_pgrp = NULL;
-       sig->tty = NULL;
-
-       sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
-       sig->gtime = cputime_zero;
-       sig->cgtime = cputime_zero;
-       sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
-       sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
-       sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
-       task_io_accounting_init(&sig->ioac);
-       sig->sum_sched_runtime = 0;
-       taskstats_tgid_init(sig);
-
        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);
 
-       acct_init_pacct(&sig->pacct);
-
        tty_audit_fork(sig);
 
-       return 0;
-}
-
-void __cleanup_signal(struct signal_struct *sig)
-{
-       thread_group_cputime_free(sig);
-       tty_kref_put(sig->tty);
-       kmem_cache_free(signal_cachep, sig);
-}
+       sig->oom_adj = current->signal->oom_adj;
 
-static void cleanup_signal(struct task_struct *tsk)
-{
-       struct signal_struct *sig = tsk->signal;
-
-       atomic_dec(&sig->live);
-
-       if (atomic_dec_and_test(&sig->count))
-               __cleanup_signal(sig);
+       return 0;
 }
 
 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
@@ -908,9 +923,9 @@ SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 
 static void rt_mutex_init_task(struct task_struct *p)
 {
-       spin_lock_init(&p->pi_lock);
+       raw_spin_lock_init(&p->pi_lock);
 #ifdef CONFIG_RT_MUTEXES
-       plist_head_init(&p->pi_waiters, &p->pi_lock);
+       plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
        p->pi_blocked_on = NULL;
 #endif
 }
@@ -973,6 +988,16 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
                return ERR_PTR(-EINVAL);
 
+       /*
+        * Siblings of global init remain as zombies on exit since they are
+        * not reaped by their parent (swapper). To solve this and to avoid
+        * multi-rooted process trees, prevent global and container-inits
+        * from creating siblings.
+        */
+       if ((clone_flags & CLONE_PARENT) &&
+                               current->signal->flags & SIGNAL_UNKILLABLE)
+               return ERR_PTR(-EINVAL);
+
        retval = security_task_create(clone_flags);
        if (retval)
                goto fork_out;
@@ -992,7 +1017,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 #endif
        retval = -EAGAIN;
        if (atomic_read(&p->real_cred->user->processes) >=
-                       p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
+                       task_rlimit(p, RLIMIT_NPROC)) {
                if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
                    p->real_cred->user != INIT_USER)
                        goto bad_fork_free;
@@ -1014,18 +1039,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        if (!try_module_get(task_thread_info(p)->exec_domain->module))
                goto bad_fork_cleanup_count;
 
-       if (p->binfmt && !try_module_get(p->binfmt->module))
-               goto bad_fork_cleanup_put_domain;
-
        p->did_exec = 0;
        delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
        copy_flags(clone_flags, p);
        INIT_LIST_HEAD(&p->children);
        INIT_LIST_HEAD(&p->sibling);
-#ifdef CONFIG_PREEMPT_RCU
-       p->rcu_read_lock_nesting = 0;
-       p->rcu_flipctr_idx = 0;
-#endif /* #ifdef CONFIG_PREEMPT_RCU */
+       rcu_copy_process(p);
        p->vfork_done = NULL;
        spin_lock_init(&p->alloc_lock);
 
@@ -1036,8 +1055,13 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        p->gtime = cputime_zero;
        p->utimescaled = cputime_zero;
        p->stimescaled = cputime_zero;
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
        p->prev_utime = cputime_zero;
        p->prev_stime = cputime_zero;
+#endif
+#if defined(SPLIT_RSS_COUNTING)
+       memset(&p->rss_stat, 0, sizeof(p->rss_stat));
+#endif
 
        p->default_timer_slack_ns = current->timer_slack_ns;
 
@@ -1062,6 +1086,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        }
        mpol_fix_fork_child_flag(p);
 #endif
+#ifdef CONFIG_CPUSETS
+       p->cpuset_mem_spread_rotor = node_random(p->mems_allowed);
+       p->cpuset_slab_spread_rotor = node_random(p->mems_allowed);
+#endif
 #ifdef CONFIG_TRACE_IRQFLAGS
        p->irq_events = 0;
 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
@@ -1090,13 +1118,15 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 #ifdef CONFIG_DEBUG_MUTEXES
        p->blocked_on = NULL; /* not blocked yet */
 #endif
-
-       p->bts = NULL;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+       p->memcg_batch.do_batch = 0;
+       p->memcg_batch.memcg = NULL;
+#endif
 
        /* Perform scheduler related setup. Assign this task to a CPU. */
        sched_fork(p, clone_flags);
 
-       retval = perf_counter_init_task(p);
+       retval = perf_event_init_task(p);
        if (retval)
                goto bad_fork_cleanup_policy;
 
@@ -1167,9 +1197,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                p->sas_ss_sp = p->sas_ss_size = 0;
 
        /*
-        * Syscall tracing should be turned off in the child regardless
-        * of CLONE_PTRACE.
+        * Syscall tracing and stepping should be turned off in the
+        * child regardless of CLONE_PTRACE.
         */
+       user_disable_single_step(p);
        clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
 #ifdef TIF_SYSCALL_EMU
        clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
@@ -1197,21 +1228,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        /* Need tasklist lock for parent etc handling! */
        write_lock_irq(&tasklist_lock);
 
-       /*
-        * The task hasn't been attached yet, so its cpus_allowed mask will
-        * not be changed, nor will its assigned CPU.
-        *
-        * The cpus_allowed mask of the parent may have changed after it was
-        * copied first time - so re-copy it here, then check the child's CPU
-        * to ensure it is on a valid CPU (and if not, just force it back to
-        * parent's CPU). This avoids alot of nasty races.
-        */
-       p->cpus_allowed = current->cpus_allowed;
-       p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
-       if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
-                       !cpu_online(task_cpu(p))))
-               set_task_cpu(p, smp_processor_id());
-
        /* CLONE_PARENT re-uses the old parent */
        if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
                p->real_parent = current->real_parent;
@@ -1240,12 +1256,14 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        }
 
        if (clone_flags & CLONE_THREAD) {
+               current->signal->nr_threads++;
+               atomic_inc(&current->signal->live);
+               atomic_inc(&current->signal->sigcnt);
                p->group_leader = current->group_leader;
                list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
        }
 
        if (likely(p->pid)) {
-               list_add_tail(&p->sibling, &p->real_parent->children);
                tracehook_finish_clone(p, clone_flags, trace);
 
                if (thread_group_leader(p)) {
@@ -1253,10 +1271,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                                p->nsproxy->pid_ns->child_reaper = p;
 
                        p->signal->leader_pid = pid;
-                       tty_kref_put(p->signal->tty);
                        p->signal->tty = tty_kref_get(current->signal->tty);
                        attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
                        attach_pid(p, PIDTYPE_SID, task_session(current));
+                       list_add_tail(&p->sibling, &p->real_parent->children);
                        list_add_tail_rcu(&p->tasks, &init_task.tasks);
                        __get_cpu_var(process_counts)++;
                }
@@ -1269,20 +1287,23 @@ static struct task_struct *copy_process(unsigned long clone_flags,
        write_unlock_irq(&tasklist_lock);
        proc_fork_connector(p);
        cgroup_post_fork(p);
+       perf_event_fork(p);
        return p;
 
 bad_fork_free_pid:
        if (pid != &init_struct_pid)
                free_pid(pid);
 bad_fork_cleanup_io:
-       put_io_context(p->io_context);
+       if (p->io_context)
+               exit_io_context(p);
 bad_fork_cleanup_namespaces:
        exit_task_namespaces(p);
 bad_fork_cleanup_mm:
        if (p->mm)
                mmput(p->mm);
 bad_fork_cleanup_signal:
-       cleanup_signal(p);
+       if (!(clone_flags & CLONE_THREAD))
+               free_signal_struct(p->signal);
 bad_fork_cleanup_sighand:
        __cleanup_sighand(p->sighand);
 bad_fork_cleanup_fs:
@@ -1294,21 +1315,17 @@ bad_fork_cleanup_semundo:
 bad_fork_cleanup_audit:
        audit_free(p);
 bad_fork_cleanup_policy:
-       perf_counter_free_task(p);
+       perf_event_free_task(p);
 #ifdef CONFIG_NUMA
        mpol_put(p->mempolicy);
 bad_fork_cleanup_cgroup:
 #endif
        cgroup_exit(p, cgroup_callbacks_done);
        delayacct_tsk_free(p);
-       if (p->binfmt)
-               module_put(p->binfmt->module);
-bad_fork_cleanup_put_domain:
        module_put(task_thread_info(p)->exec_domain->module);
 bad_fork_cleanup_count:
        atomic_dec(&p->cred->user->processes);
-       put_cred(p->real_cred);
-       put_cred(p->cred);
+       exit_creds(p);
 bad_fork_free:
        free_task(p);
 fork_out:
@@ -1410,9 +1427,6 @@ long do_fork(unsigned long clone_flags,
                        init_completion(&vfork);
                }
 
-               if (!(clone_flags & CLONE_THREAD))
-                       perf_counter_fork(p);
-
                audit_finish_fork(p);
                tracehook_report_clone(regs, clone_flags, nr, p);
 
@@ -1504,14 +1518,6 @@ static void check_unshare_flags(unsigned long *flags_ptr)
                *flags_ptr |= CLONE_SIGHAND;
 
        /*
-        * If unsharing signal handlers and the task was created
-        * using CLONE_THREAD, then must unshare the thread
-        */
-       if ((*flags_ptr & CLONE_SIGHAND) &&
-           (atomic_read(&current->signal->count) > 1))
-               *flags_ptr |= CLONE_THREAD;
-
-       /*
         * If unsharing namespace, must also unshare filesystem information.
         */
        if (*flags_ptr & CLONE_NEWNS)