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    Subject[PATCH] CMWQ: Set workqueue name before we process one work.
    Date
    Now in CMWQ, workqueue threads are named as 'kworker/*'. So it is
    a little boring to see in the 'top'(below) and actually it isn't
    meaningful for the users.
    12606 root 20 0 0 0 0 S 2 0.0 0:03.22 kworker/u:0
    12607 root 20 0 0 0 0 S 1 0.0 0:03.69 kworker/u:4

    So this patch just try to set the proper workqueue name if it does
    exist. Yes, workqueue now is a thread pool and the data may be not
    accurate but I think it is better(below) than the 'kworker*' stuff.
    And if there is something block the workqueue, we can find the caller
    easily.
    12606 root 20 0 0 0 0 D 2 0.0 0:02.90 dlm_wq
    12607 root 20 0 0 0 0 D 0 0.0 0:03.21 ocfs2_wq

    What's more, in ocfs2, we sometimes want to print some debug info in
    the system log and we use 'current->comm' to print the thread and this
    change also does help.

    The only thing I am not clear is that do we need [gs]et_task_comm?
    I guess not and this patch just try to use strlcpy without task_lock.

    Cc: Tejun Heo <tj@kernel.org>
    Signed-off-by: Tao Ma <tao.ma@oracle.com>
    ---
    kernel/workqueue.c | 10 ++++++++++
    1 files changed, 10 insertions(+), 0 deletions(-)

    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index 2994a0e..69402f8 100644
    --- a/kernel/workqueue.c
    +++ b/kernel/workqueue.c
    @@ -1730,6 +1730,7 @@ static void process_one_work(struct worker *worker, struct work_struct *work)
    work_func_t f = work->func;
    int work_color;
    struct worker *collision;
    + char comm_saved[TASK_COMM_LEN];
    #ifdef CONFIG_LOCKDEP
    /*
    * It is permissible to free the struct work_struct from
    @@ -1790,7 +1791,16 @@ static void process_one_work(struct worker *worker, struct work_struct *work)
    work_clear_pending(work);
    lock_map_acquire(&cwq->wq->lockdep_map);
    lock_map_acquire(&lockdep_map);
    + if (cwq->wq->name) {
    + strlcpy(comm_saved, worker->task->comm,
    + sizeof(comm_saved));
    + strlcpy(worker->task->comm, cwq->wq->name,
    + sizeof(worker->task->comm));
    + }
    f(work);
    + if (cwq->wq->name)
    + strlcpy(worker->task->comm, comm_saved,
    + sizeof(worker->task->comm));
    lock_map_release(&lockdep_map);
    lock_map_release(&cwq->wq->lockdep_map);

    --
    1.7.1.GIT


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