kgdb/serial: Short term workaround

On 07/27/2011 04:37 PM, Thomas Gleixner wrote:
>  - KGDB (not yet disabled) is reportedly unusable on -rt right now due
>    to missing hacks in the console locking which I dropped on purpose.
>

To work around this in the short term you can use this patch, in
addition to the clocksource watchdog patch that Thomas brewed up.

Comments are welcome of course.  Ultimately the right solution is to
change separation between the console and the HW to have a polled mode
+ work queue so as not to introduce any kind of latency.

Thanks,
Jason.

1 files changed, 2 insertions, 4 deletions

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index bb9520f0f6ff..eb68a9dd0f11 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -553,7 +553,6 @@ int vkdb_printf(const char *fmt, va_list ap)
 	int diag;
 	int linecount;
 	int logging, saved_loglevel = 0;
-	int saved_trap_printk;
 	int got_printf_lock = 0;
 	int retlen = 0;
 	int fnd, len;
@@ -564,8 +563,6 @@ int vkdb_printf(const char *fmt, va_list ap)
 	unsigned long uninitialized_var(flags);
 
 	preempt_disable();
-	saved_trap_printk = kdb_trap_printk;
-	kdb_trap_printk = 0;
 
 	/* Serialize kdb_printf if multiple cpus try to write at once.
 	 * But if any cpu goes recursive in kdb, just print the output,
@@ -821,7 +818,6 @@ kdb_print_out:
 	} else {
 		__release(kdb_printf_lock);
 	}
-	kdb_trap_printk = saved_trap_printk;
 	preempt_enable();
 	return retlen;
 }
@@ -831,9 +827,11 @@ int kdb_printf(const char *fmt, ...)
 	va_list ap;
 	int r;
 
+	kdb_trap_printk++;
 	va_start(ap, fmt);
 	r = vkdb_printf(fmt, ap);
 	va_end(ap);
+	kdb_trap_printk--;
 
 	return r;
 }