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    Subject[PATCH] loop: potential kernel hang waiting for kthread

    Hi Andrew! Folks!

    just stumbled over the following issue with loop_set_fd()
    calling kernel_thread(loop_thread), ignoring the return
    value, even if it is an error, then doing wait_for_completion()
    on the device, which, in beforementioned error case, would
    wait forever (keeping a process stuck in 'D' state)

    I can imagine at least three other solutions, but this
    one seemed quite organic to me, YMMV ...

    best,
    Herbert

    Signed-off-by: Herbert Poetzl <herbert@13thfloor.at>
    ---
    --- linux/drivers/block/loop.c 2006-03-24 03:37:07 +0100
    +++ linux/drivers/block/loop.c 2006-03-25 02:30:37 +0100
    @@ -747,6 +747,7 @@ static int loop_set_fd(struct loop_devic
    int lo_flags = 0;
    int error;
    loff_t size;
    + pid_t pid;

    /* This is safe, since we have a reference from open(). */
    __module_get(THIS_MODULE);
    @@ -839,10 +840,14 @@ static int loop_set_fd(struct loop_devic

    set_blocksize(bdev, lo_blocksize);

    - kernel_thread(loop_thread, lo, CLONE_KERNEL);
    + pid = kernel_thread(loop_thread, lo, CLONE_KERNEL);
    + if (pid < 0)
    + goto out_err;
    wait_for_completion(&lo->lo_done);
    return 0;

    + out_err:
    + error = (int)pid;
    out_putf:
    fput(file);
    out:
    -
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