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workaround serial hang with SMP enabled 

SVN-Revision: 22557
lede-17.01
Imre Kaloz 2010-08-09 11:27:14 +00:00
parent 0f5d0f69ab
commit 16478f7dd6
1 changed files with 39 additions and 0 deletions
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39
target/linux/cns3xxx/patches-2.6.31/210-cns3xxx_smp_serial_fix.patch Normal file
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@ -0,0 +1,39 @@
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1743,6 +1743,7 @@ static void serial8250_backup_timeout(un
unsigned int iir, ier = 0, lsr;
unsigned long flags;
+ spin_lock_irqsave(&up->port.lock, flags);
/*
* Must disable interrupts or else we risk racing with the interrupt
* based handler.
@@ -1760,10 +1761,8 @@ static void serial8250_backup_timeout(un
* the "Diva" UART used on the management processor on many HP
* ia64 and parisc boxes.
*/
- spin_lock_irqsave(&up->port.lock, flags);
lsr = serial_in(up, UART_LSR);
up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
- spin_unlock_irqrestore(&up->port.lock, flags);
if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&
(!uart_circ_empty(&up->port.info->xmit) || up->port.x_char) &&
(lsr & UART_LSR_THRE)) {
@@ -1771,12 +1770,14 @@ static void serial8250_backup_timeout(un
iir |= UART_IIR_THRI;
}
- if (!(iir & UART_IIR_NO_INT))
- serial8250_handle_port(up);
-
if (is_real_interrupt(up->port.irq))
serial_out(up, UART_IER, ier);
+ spin_unlock_irqrestore(&up->port.lock, flags);
+
+ if (!(iir & UART_IIR_NO_INT))
+ serial8250_handle_port(up);
+
/* Standard timer interval plus 0.2s to keep the port running */
mod_timer(&up->timer,
jiffies + poll_timeout(up->port.timeout) + HZ / 5);