serial: samsung: fix potential soft lockup during uart write
Certain tty line discipline implementations such slip and bluetooth hci invoke the serial core uart_write() api in their write_wakeup callback. This leads to a soft lockup with samsung serial driver since the uart port lock is taken in the driver's interrupt handler and uart_write() attempts to take the same lock again. Fix this issue by releasing the uart port lock before the call to uart_write_wakeup() in the tx handler. Also move the spin-lock/unlock sequence from s3c64xx_serial_handle_irq() function into the tx and rx irq handlers so that this change is applicable to s3c24xx platforms as well. Reported-by: Kyungmin Park <kyungmin.park@samsung.com> Reported-by: Hyeonkook Kim <hk619.kim@samsung.com> Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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daa74a25cc
Коммит
c15c3747ee
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@ -223,8 +223,11 @@ s3c24xx_serial_rx_chars(int irq, void *dev_id)
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struct uart_port *port = &ourport->port;
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struct tty_struct *tty = port->state->port.tty;
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unsigned int ufcon, ch, flag, ufstat, uerstat;
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unsigned long flags;
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int max_count = 64;
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spin_lock_irqsave(&port->lock, flags);
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while (max_count-- > 0) {
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ufcon = rd_regl(port, S3C2410_UFCON);
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ufstat = rd_regl(port, S3C2410_UFSTAT);
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@ -299,6 +302,7 @@ s3c24xx_serial_rx_chars(int irq, void *dev_id)
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tty_flip_buffer_push(tty);
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out:
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spin_unlock_irqrestore(&port->lock, flags);
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return IRQ_HANDLED;
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}
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@ -307,8 +311,11 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id)
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struct s3c24xx_uart_port *ourport = id;
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struct uart_port *port = &ourport->port;
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struct circ_buf *xmit = &port->state->xmit;
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unsigned long flags;
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int count = 256;
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spin_lock_irqsave(&port->lock, flags);
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if (port->x_char) {
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wr_regb(port, S3C2410_UTXH, port->x_char);
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port->icount.tx++;
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@ -336,13 +343,17 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id)
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port->icount.tx++;
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}
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if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
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if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) {
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spin_unlock(&port->lock);
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uart_write_wakeup(port);
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spin_lock(&port->lock);
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}
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if (uart_circ_empty(xmit))
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s3c24xx_serial_stop_tx(port);
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out:
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spin_unlock_irqrestore(&port->lock, flags);
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return IRQ_HANDLED;
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}
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@ -352,10 +363,8 @@ static irqreturn_t s3c64xx_serial_handle_irq(int irq, void *id)
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struct s3c24xx_uart_port *ourport = id;
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struct uart_port *port = &ourport->port;
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unsigned int pend = rd_regl(port, S3C64XX_UINTP);
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unsigned long flags;
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irqreturn_t ret = IRQ_HANDLED;
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spin_lock_irqsave(&port->lock, flags);
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if (pend & S3C64XX_UINTM_RXD_MSK) {
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ret = s3c24xx_serial_rx_chars(irq, id);
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wr_regl(port, S3C64XX_UINTP, S3C64XX_UINTM_RXD_MSK);
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@ -364,7 +373,6 @@ static irqreturn_t s3c64xx_serial_handle_irq(int irq, void *id)
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ret = s3c24xx_serial_tx_chars(irq, id);
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wr_regl(port, S3C64XX_UINTP, S3C64XX_UINTM_TXD_MSK);
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}
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spin_unlock_irqrestore(&port->lock, flags);
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return ret;
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}
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