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    Subject[PATCH 52/80] vt: remove bogus lock dropping
    Date
    From: Alan Cox <alan@redhat.com>

    For hysterical raisins the vt layer drops and retakes locks in the write
    method. This is a left over from the days when user/kernel data was passed
    directly to the tty not pre-buffered.

    Signed-off-by: Alan Cox <alan@redhat.com>
    ---

    drivers/char/vt.c | 18 ------------------
    1 files changed, 0 insertions(+), 18 deletions(-)


    diff --git a/drivers/char/vt.c b/drivers/char/vt.c
    index 05ca1c5..ec94521 100644
    --- a/drivers/char/vt.c
    +++ b/drivers/char/vt.c
    @@ -2136,27 +2136,9 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
    release_console_sem();
    return 0;
    }
    - release_console_sem();
    -
    orig_buf = buf;
    orig_count = count;

    - /* At this point 'buf' is guaranteed to be a kernel buffer
    - * and therefore no access to userspace (and therefore sleeping)
    - * will be needed. The con_buf_mtx serializes all tty based
    - * console rendering and vcs write/read operations. We hold
    - * the console spinlock during the entire write.
    - */
    -
    - acquire_console_sem();
    -
    - vc = tty->driver_data;
    - if (vc == NULL) {
    - printk(KERN_ERR "vt: argh, driver_data _became_ NULL !\n");
    - release_console_sem();
    - goto out;
    - }
    -
    himask = vc->vc_hi_font_mask;
    charmask = himask ? 0x1ff : 0xff;



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