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serial: core: Remove unsafe x_char optimization
uart_unthrottle() attempts to avoid sending START and the previous x_char if the previous x_char has not yet been sent. However, this optimization could leave the sender in a throttled state; for example, if the sender is throttled and this unthrottle coincides with a manual tcflow(TCION) from user-space, then neither START would be sent. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -647,12 +647,8 @@ static void uart_unthrottle(struct tty_struct *tty)
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mask &= ~port->flags;
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mask &= ~port->flags;
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}
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}
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if (mask & UPF_SOFT_FLOW) {
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if (mask & UPF_SOFT_FLOW)
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if (port->x_char)
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uart_send_xchar(tty, START_CHAR(tty));
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port->x_char = 0;
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else
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uart_send_xchar(tty, START_CHAR(tty));
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}
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if (mask & UPF_HARD_FLOW)
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if (mask & UPF_HARD_FLOW)
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uart_set_mctrl(port, TIOCM_RTS);
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uart_set_mctrl(port, TIOCM_RTS);
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