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    SubjectRe: [PATCH] tty: hold lock across tty buffer finding and buffer filling
    On 03/16/2012 10:49 AM, Du, Alek wrote:
    > The tty structure is protect and not null, the tty->buf.tail is null. Many people think the tty reference count isn't protected and cause this bug, it is not true. :-)

    You protect the pointer, not what is inside that structure. If you
    increment a tty reference count, tty->buf.tail won't be NULL iff tty is
    not NULL. IOW, you have to use tty_port_tty_set/get all around.

    > For the flush case, it need acquire the spinlock to free the buffer and put buf.tail to NULL. So this patch will help:
    > Here is the example place, you can see the __tty_buffer_flush is inside the spinlock.

    I'm not talking about flush. I'm talking about prepare. It returns a
    pointer to a tty buffer which may be concurrently freed by flush.

    A B
    memcpy(chars, data_from_HW); <- chars is freed now

    suse labs

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      Last update: 2012-03-16 10:59    [W:0.022 / U:18.744 seconds]
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