Deprecate find_task_by_pid()

There are some places that are known to operate on tasks'
global pids only:

* the rest_init() call (called on boot)
* the kgdb's getthread
* the create_kthread() (since the kthread is run in init ns)

So use the find_task_by_pid_ns(..., &init_pid_ns) there
and schedule the find_task_by_pid for removal.

[sukadev@us.ibm.com: Fix warning in kernel/pid.c]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 24 insertions, 9 deletions

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 599fe55bf297..3c35d452b1a9 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -138,6 +138,24 @@ Who:	Kay Sievers <kay.sievers@suse.de>
 
 ---------------------------
 
+What:   find_task_by_pid
+When:   2.6.26
+Why:    With pid namespaces, calling this funciton will return the
+        wrong task when called from inside a namespace.
+
+        The best way to save a task pid and find a task by this
+        pid later, is to find this task's struct pid pointer (or get
+        it directly from the task) and call pid_task() later.
+
+        If someone really needs to get a task by its pid_t, then
+        he most likely needs the find_task_by_vpid() to get the
+        task from the same namespace as the current task is in, but
+        this may be not so in general.
+
+Who:    Pavel Emelyanov <xemul@openvz.org>
+
+---------------------------
+
 What:   ACPI procfs interface
 When:   July 2008
 Why:    ACPI sysfs conversion should be finished by January 2008.
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 86e60796db62..03c238088aee 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1677,7 +1677,10 @@ extern struct pid_namespace init_pid_ns;
 extern struct task_struct *find_task_by_pid_type_ns(int type, int pid,
                 struct pid_namespace *ns);
 
-extern struct task_struct *find_task_by_pid(pid_t nr);
+static inline struct task_struct *__deprecated find_task_by_pid(pid_t nr)
+{
+        return find_task_by_pid_type_ns(PIDTYPE_PID, nr, &init_pid_ns);
+}
 extern struct task_struct *find_task_by_vpid(pid_t nr);
 extern struct task_struct *find_task_by_pid_ns(pid_t nr,
                 struct pid_namespace *ns);
diff --git a/init/main.c b/init/main.c
index 1f4406477f83..dff253cfcd9f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -459,7 +459,7 @@ static void noinline __init_refok rest_init(void)
         kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
         numa_default_policy();
         pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
-        kthreadd_task = find_task_by_pid(pid);
+        kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
         unlock_kernel();
 
         /*
diff --git a/kernel/kthread.c b/kernel/kthread.c
index ac72eea48339..bd1b9ea024e1 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -98,7 +98,7 @@ static void create_kthread(struct kthread_create_info *create)
                 struct sched_param param = { .sched_priority = 0 };
                 wait_for_completion(&create->started);
                 read_lock(&tasklist_lock);
-                create->result = find_task_by_pid(pid);
+                create->result = find_task_by_pid_ns(pid, &init_pid_ns);
                 read_unlock(&tasklist_lock);
                 /*
                  * root may have changed our (kthreadd's) priority or CPU mask.
diff --git a/kernel/pid.c b/kernel/pid.c
index b322cdf401bf..a9ae9f7fb229 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -381,12 +381,6 @@ struct task_struct *find_task_by_pid_type_ns(int type, int nr,
 
 EXPORT_SYMBOL(find_task_by_pid_type_ns);
 
-struct task_struct *find_task_by_pid(pid_t nr)
-{
-        return find_task_by_pid_type_ns(PIDTYPE_PID, nr, &init_pid_ns);
-}
-EXPORT_SYMBOL(find_task_by_pid);
-
 struct task_struct *find_task_by_vpid(pid_t vnr)
 {
         return find_task_by_pid_type_ns(PIDTYPE_PID, vnr,