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    Subject[PATCH 12/12] Deprecate the 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.

    Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

    ---
    Documentation/feature-removal-schedule.txt | 19 +++++++++++++++++++
    include/linux/sched.h | 2 +-
    init/main.c | 2 +-
    kernel/kgdb.c | 2 +-
    kernel/kthread.c | 2 +-
    5 files changed, 23 insertions(+), 4 deletions(-)

    diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
    index be6c2db..1e6960d 100644
    --- a/Documentation/feature-removal-schedule.txt
    +++ b/Documentation/feature-removal-schedule.txt
    @@ -264,3 +264,22 @@ Why: These drivers are superseded by i810fb, intelfb and savagefb.
    Who: Jean Delvare <khali@linux-fr.org>

    ---------------------------
    +
    +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>
    +
    +---------------------------
    +
    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 198659b..ccb9bba 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1617,7 +1617,7 @@ 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);
    +extern struct task_struct *find_task_by_pid(pid_t nr) __deprecated;
    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 e702632..38a16ba 100644
    --- a/init/main.c
    +++ b/init/main.c
    @@ -437,7 +437,7 @@ 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/kgdb.c b/kernel/kgdb.c
    index 87b0463..6de0fd0 100644
    --- a/kernel/kgdb.c
    +++ b/kernel/kgdb.c
    @@ -621,7 +621,7 @@ static struct task_struct *getthread(struct pt_regs *regs, int tid)
    if (!tid)
    return NULL;

    - return find_task_by_pid(tid);
    + return find_task_by_pid_ns(tid, &init_pid_ns);
    }

    #ifdef CONFIG_SMP
    diff --git a/kernel/kthread.c b/kernel/kthread.c
    index 0ac8878..b9caa46 100644
    --- a/kernel/kthread.c
    +++ b/kernel/kthread.c
    @@ -99,7 +99,7 @@ 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.
    --
    1.5.3.4


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