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    SubjectRe: [PATCH] pids: simplify do_each_task_pid/while_each_task_pid
    On 04/13, Christoph Hellwig wrote:
    >
    > This is prtty ugly. Can't we just have a
    >
    > #define for_each_task_pid(task, pid, type, pos) \
    > hlist_for_each_entry_rcu((task), (pos), \
    > (&(pid))->tasks[type], pids[type].node) {
    >
    > and move the find_pid to the caller? That would make the code a whole lot
    > more readable.

    How about this? :)

    Oleg.

    --- MM/include/linux/pid.h~ 2006-03-23 22:48:10.000000000 +0300
    +++ MM/include/linux/pid.h 2006-04-14 01:49:08.000000000 +0400
    @@ -98,22 +98,22 @@ extern void FASTCALL(free_pid(struct pid
    hlist_entry(pid_next(task, type), struct task_struct, \
    pids[(type)].node)

    +#define for_each_task_pid(who, type, t) \
    + for ((t) = ({ \
    + struct pid *pid___ = find_pid(who); \
    + pid___ \
    + ? hlist_entry((&pid___->tasks[type])->first, typeof(*(t)), pids[type].node) \
    + : hlist_entry(NULL, typeof(*(t)), pids[type].node); \
    + }); \
    + rcu_dereference(t) != hlist_entry(NULL, typeof(*(t)), pids[type].node) \
    + && ({ prefetch((t)->pids[type].node.next); 1; }); \
    + (t) = hlist_entry((t)->pids[type].node.next, typeof(*(t)), pids[type].node))

    -/* We could use hlist_for_each_entry_rcu here but it takes more arguments
    - * than the do_each_task_pid/while_each_task_pid. So we roll our own
    - * to preserve the existing interface.
    - */
    -#define do_each_task_pid(who, type, task) \
    - if ((task = find_task_by_pid_type(type, who))) { \
    - prefetch(pid_next(task, type)); \
    - do {
    +/* obsolete */
    +#define do_each_task_pid(who, type, task) \
    + do for_each_task_pid(who, type, task)

    -#define while_each_task_pid(who, type, task) \
    - } while (pid_next(task, type) && ({ \
    - task = pid_next_task(task, type); \
    - rcu_dereference(task); \
    - prefetch(pid_next(task, type)); \
    - 1; }) ); \
    - }
    +#define while_each_task_pid(who, type, task) \
    + while (0)

    #endif /* _LINUX_PID_H */
    -
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