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tty/serial: at91: handle IRQ status more safely 

Handle the changed flag of IRQ status in interruption
instead of handling it in tasklet due to the tasklet
may be scheduled more than once in one interruption.
Otherwise, the changed status may be processed more
than once which will lead to unexpected result. And
seriously, kernel will crash.

Signed-off-by: Leilei Zhao <leilei.zhao@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Leilei Zhao 2015-04-09 10:48:15 +08:00 committed by Greg Kroah-Hartman
parent 74a76089d2
commit d033e82db9
1 changed files with 7 additions and 6 deletions
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13
drivers/tty/serial/atmel_serial.c
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@ -165,6 +165,7 @@ struct atmel_uart_port {
struct tasklet_struct tasklet;
unsigned int irq_status;
unsigned int irq_status_prev;
unsigned int status_change;
struct circ_buf rx_ring;
@ -1177,6 +1178,9 @@ atmel_handle_status(struct uart_port *port, unsigned int pending,
if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
| ATMEL_US_CTSIC)) {
atmel_port->irq_status = status;
atmel_port->status_change = atmel_port->irq_status ^
atmel_port->irq_status_prev;
atmel_port->irq_status_prev = status;
tasklet_schedule(&atmel_port->tasklet);
}
}
@ -1523,17 +1527,14 @@ static void atmel_tasklet_func(unsigned long data)
{
struct uart_port *port = (struct uart_port *)data;
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
unsigned int status;
unsigned int status_change;
unsigned int status = atmel_port->irq_status;
unsigned int status_change = atmel_port->status_change;
/* The interrupt handler does not take the lock */
spin_lock(&port->lock);
atmel_port->schedule_tx(port);
status = atmel_port->irq_status;
status_change = status ^ atmel_port->irq_status_prev;
if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
| ATMEL_US_DCD | ATMEL_US_CTS)) {
/* TODO: All reads to CSR will clear these interrupts! */
@ -1548,7 +1549,7 @@ static void atmel_tasklet_func(unsigned long data)
wake_up_interruptible(&port->state->port.delta_msr_wait);
atmel_port->irq_status_prev = status;
atmel_port->status_change = 0;
}
atmel_port->schedule_rx(port);