Messages in this thread Patch in this message | | | Date | Wed, 03 Oct 2007 18:19:01 +0400 | From | Pavel Emelyanov <> | Subject | [PATCH 1/3] Introduce the dummy_pid |
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This is a pid which is attached to tasks when they detach their pids. This is done in detach_pid() and transfer_pid(). The pid_alive() check is changed to reflect this fact.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
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diff --git a/include/linux/sched.h b/include/linux/sched.h index 4f21af1..e17b8f8 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1286,9 +1286,11 @@ static inline pid_t task_ppid_nr_ns(stru * If pid_alive fails, then pointers within the task structure * can be stale and must not be dereferenced. */ +extern struct pid dummy_pid; + static inline int pid_alive(struct task_struct *p) { - return p->pids[PIDTYPE_PID].pid != NULL; + return p->pids[PIDTYPE_PID].pid != &dummy_pid; } /** diff --git a/kernel/pid.c b/kernel/pid.c index d7388d7..b7a11cf 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -81,6 +81,17 @@ struct pid_namespace init_pid_ns = { }; EXPORT_SYMBOL_GPL(init_pid_ns); +struct pid dummy_pid = { + .count = ATOMIC_INIT(1), + .numbers = { { + .nr = 0, /* this is what pid_nr will return + * for tasks with no pids + */ + .ns = &init_pid_ns, + }, } +}; +EXPORT_SYMBOL(dummy_pid); + int is_cgroup_init(struct task_struct *tsk) { int ret = 0; @@ -339,7 +350,7 @@ void fastcall detach_pid(struct task_str pid = link->pid; hlist_del_rcu(&link->node); - link->pid = NULL; + link->pid = &dummy_pid; for (tmp = PIDTYPE_MAX; --tmp >= 0; ) if (!hlist_empty(&pid->tasks[tmp])) @@ -354,7 +365,7 @@ void fastcall transfer_pid(struct task_s { new->pids[type].pid = old->pids[type].pid; hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); - old->pids[type].pid = NULL; + old->pids[type].pid = &dummy_pid; } struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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