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Subject: rt: Improve the serial console PASS_LIMIT
From: Ingo Molnar <mingo@elte.hu>
Date: Wed Dec 14 13:05:54 CET 2011
Beyond the warning:
drivers/tty/serial/8250/8250.c:1613:6: warning: unused variable ‘pass_counter’ [-Wunused-variable]
the solution of just looping infinitely was ugly - up it to 1 million to
give it a chance to continue in some really ugly situation.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
drivers/tty/serial/8250/8250.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
Index: linux-stable/drivers/tty/serial/8250/8250.c
===================================================================
--- linux-stable.orig/drivers/tty/serial/8250/8250.c
+++ linux-stable/drivers/tty/serial/8250/8250.c
@@ -80,7 +80,16 @@ static unsigned int skip_txen_test; /* f
#define DEBUG_INTR(fmt...) do { } while (0)
#endif
-#define PASS_LIMIT 512
+/*
+ * On -rt we can have a more delays, and legitimately
+ * so - so don't drop work spuriously and spam the
+ * syslog:
+ */
+#ifdef CONFIG_PREEMPT_RT_FULL
+# define PASS_LIMIT 1000000
+#else
+# define PASS_LIMIT 512
+#endif
#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
@@ -1549,14 +1558,12 @@ static irqreturn_t serial8250_interrupt(
l = l->next;
-#ifndef CONFIG_PREEMPT_RT_FULL
if (l == i->head && pass_counter++ > PASS_LIMIT) {
/* If we hit this, we're dead. */
printk_ratelimited(KERN_ERR
"serial8250: too much work for irq%d\n", irq);
break;
}
-#endif
} while (l != end);
spin_unlock(&i->lock);
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