commit c95ea73afce29a9c47bab29787d6eb014a8de9e6 Author: Stas Date: Mon Apr 11 15:06:33 2011 +0400 implement PR_DETACH diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h index 942d30b..1da9c20 100644 --- a/include/asm-generic/siginfo.h +++ b/include/asm-generic/siginfo.h @@ -218,7 +218,8 @@ typedef struct siginfo { #define CLD_TRAPPED (__SI_CHLD|4) /* traced child has trapped */ #define CLD_STOPPED (__SI_CHLD|5) /* child has stopped */ #define CLD_CONTINUED (__SI_CHLD|6) /* stopped child has continued */ -#define NSIGCHLD 6 +#define CLD_DETACHED (__SI_CHLD|7) /* child has detached */ +#define NSIGCHLD 7 /* * SIGPOLL si_codes diff --git a/include/linux/init_task.h b/include/linux/init_task.h index caa151f..fdf71a9 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -158,6 +158,8 @@ extern struct cred init_cred; .parent = &tsk, \ .children = LIST_HEAD_INIT(tsk.children), \ .sibling = LIST_HEAD_INIT(tsk.sibling), \ + .detached_children = LIST_HEAD_INIT(tsk.detached_children),\ + .detached_sibling = LIST_HEAD_INIT(tsk.detached_sibling), \ .group_leader = &tsk, \ RCU_INIT_POINTER(.real_cred, &init_cred), \ RCU_INIT_POINTER(.cred, &init_cred), \ diff --git a/include/linux/prctl.h b/include/linux/prctl.h index a3baeb2..fbd2451 100644 --- a/include/linux/prctl.h +++ b/include/linux/prctl.h @@ -102,4 +102,6 @@ #define PR_MCE_KILL_GET 34 +#define PR_DETACH 35 + #endif /* _LINUX_PRCTL_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index e74882f..c8a1741 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1260,6 +1260,9 @@ struct task_struct { /* task state */ int exit_state; int exit_code, exit_signal; + int detach_code; + int detaching; + int is_detaching:1; int pdeath_signal; /* The signal sent when the parent dies */ /* ??? */ unsigned int personality; @@ -1292,6 +1295,8 @@ struct task_struct { */ struct list_head children; /* list of my children */ struct list_head sibling; /* linkage in my parent's children list */ + struct list_head detached_children; /* list of my detached children */ + struct list_head detached_sibling; /* linkage in my parent's detached children list */ struct task_struct *group_leader; /* threadgroup leader */ /* diff --git a/kernel/exit.c b/kernel/exit.c index 2aa64e8..a2c5cfb 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -69,6 +69,7 @@ static void __unhash_process(struct task_struct *p, bool group_dead) list_del_rcu(&p->tasks); list_del_init(&p->sibling); + list_del_init(&p->detached_sibling); __this_cpu_dec(process_counts); } list_del_rcu(&p->thread_group); @@ -804,6 +805,17 @@ static void forget_original_parent(struct task_struct *father) } while_each_thread(p, t); reparent_leader(father, p, &dead_children); } + list_for_each_entry_safe(p, n, &father->detached_children, + detached_sibling) { + int signal; + p->detaching = 0; + p->is_detaching = 0; + list_del_init(&p->detached_sibling); + if (p->exit_state == EXIT_ZOMBIE) { + signal = do_notify_parent(p, SIGCHLD); + BUG_ON(signal == DEATH_REAP); + } + } write_unlock_irq(&tasklist_lock); BUG_ON(!list_empty(&father->children)); @@ -858,7 +870,8 @@ static void exit_notify(struct task_struct *tsk, int group_dead) tsk->exit_signal = SIGCHLD; signal = tracehook_notify_death(tsk, &cookie, group_dead); - if (signal >= 0) + /* delay parent notification for detaching tasks */ + if (signal >= 0 && !tsk->is_detaching) signal = do_notify_parent(tsk, signal); tsk->exit_state = signal == DEATH_REAP ? EXIT_DEAD : EXIT_ZOMBIE; @@ -1507,6 +1520,54 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) return retval; } +static int wait_task_detached(struct wait_opts *wo, struct task_struct *p) +{ + int dt, signal, retval = 0; + pid_t pid; + uid_t uid; + + if (!likely(wo->wo_flags & WEXITED)) + return 0; + + if (unlikely(wo->wo_flags & WNOWAIT)) { + get_task_struct(p); + read_unlock(&tasklist_lock); + pid = task_pid_vnr(p); + uid = __task_cred(p)->uid; + return wait_noreap_copyout(wo, p, pid, uid, CLD_DETACHED, + p->detach_code >> 8); + } + + dt = xchg(&p->detaching, 0); + if (dt != 1) + return 0; + get_task_struct(p); + read_unlock(&tasklist_lock); + + write_lock_irq(&tasklist_lock); + list_del_init(&p->detached_sibling); + if (p->exit_state == EXIT_ZOMBIE) { + signal = do_notify_parent(p, SIGCHLD); + BUG_ON(signal == DEATH_REAP); + } + p->is_detaching = 0; + write_unlock_irq(&tasklist_lock); + + if (wo->wo_stat) + retval = put_user(p->detach_code, wo->wo_stat); + + if (!retval) { + pid = task_pid_vnr(p); + uid = __task_cred(p)->uid; + retval = wait_noreap_copyout(wo, p, pid, uid, CLD_DETACHED, + p->detach_code >> 8); + } else { + put_task_struct(p); + } + + return retval; +} + static int can_wait_task_common(struct wait_opts *wo, struct task_struct *p) { int ret = eligible_child(wo, p); @@ -1572,7 +1633,8 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace, /* * We don't reap group leaders with subthreads. */ - if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p)) + if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p) && + !p->is_detaching) return wait_task_zombie(wo, p); /* @@ -1610,6 +1672,15 @@ static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk) return ret; } + list_for_each_entry(p, &tsk->detached_children, detached_sibling) { + ret = can_wait_task(wo, p); + if (!ret) + continue; + ret = wait_task_detached(wo, p); + if (ret) + return ret; + } + return 0; } diff --git a/kernel/fork.c b/kernel/fork.c index 25e4291..feadef7 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1070,6 +1070,8 @@ static struct task_struct *copy_process(unsigned long clone_flags, copy_flags(clone_flags, p); INIT_LIST_HEAD(&p->children); INIT_LIST_HEAD(&p->sibling); + INIT_LIST_HEAD(&p->detached_children); + INIT_LIST_HEAD(&p->detached_sibling); rcu_copy_process(p); p->vfork_done = NULL; spin_lock_init(&p->alloc_lock); @@ -1233,6 +1235,8 @@ static struct task_struct *copy_process(unsigned long clone_flags, p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); p->pdeath_signal = 0; p->exit_state = 0; + p->detaching = 0; + p->is_detaching = 0; /* * Ok, make it visible to the rest of the system. diff --git a/kernel/sys.c b/kernel/sys.c index 18da702..1d88ee8 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include #include @@ -1736,6 +1737,41 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, else error = PR_MCE_KILL_DEFAULT; break; + case PR_DETACH: { + struct task_struct *p, *leader; + int notif; + struct pid_namespace *pid_ns = task_active_pid_ns(me); + error = -EPERM; + /* not detaching from init */ + if (same_thread_group(me->real_parent, + pid_ns->child_reaper)) + break; + if (arg2 & ~0x7f) + break; + write_lock_irq(&tasklist_lock); + leader = me->group_leader; + leader->detach_code = arg2 << 8; + notif = do_signal_parent(leader, leader->exit_signal, + CLD_DETACHED, arg2); + if (notif != DEATH_REAP) { + list_add_tail(&leader->detached_sibling, + &leader->real_parent->detached_children); + leader->detaching = 1; + leader->is_detaching = 1; + } + p = leader; + do { + if (!task_ptrace(p)) + p->parent = pid_ns->child_reaper; + p->real_parent = pid_ns->child_reaper; + } while_each_thread(leader, p); + list_move_tail(&leader->sibling, + &leader->real_parent->children); + leader->exit_signal = SIGCHLD; + write_unlock_irq(&tasklist_lock); + error = 0; + break; + } default: error = -EINVAL; break;