WARNING: this is a hack to support debugging.


For CONFIG_PREEMPT_RT_FULL console_trylock_for_printk() will not attempt to
lock the console if:
   !early_boot_irqs_disabled && !irqs_disabled_flags(flags) && !preempt_count()
thus vprintk() will not print out the buffers.

Allow console_trylock_for_printk() attempt to lock the console if
sysrq_in_progress.

This hack patch sets oops_in_progress so that sysrq output can maybe get
delivered to the console without delay.


Using oops_in_progress is important because that also affects the locking
methods used by the serial driver.


---
 kernel/printk.c |    5 	3 +	2 -	0 !
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: b/kernel/printk.c
===================================================================
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -824,8 +824,9 @@ static int console_trylock_for_printk(un
 	__releases(&logbuf_lock)
 {
 #ifdef CONFIG_PREEMPT_RT_FULL
-	int lock = !early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
-		!preempt_count();
+	int lock = oops_in_progress ||
+		(!early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
+		!preempt_count());
 #else
 	int lock = 1;
 #endif
---
 drivers/tty/sysrq.c |    3 	3 +	0 -	0 !
 1 file changed, 3 insertions(+)

Index: b/drivers/tty/sysrq.c
===================================================================
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -499,6 +499,8 @@ void __handle_sysrq(int key, bool check_
 	int i;
 	unsigned long flags;
 
+int save_oops_in_progress = oops_in_progress;
+oops_in_progress = 1;
 	spin_lock_irqsave(&sysrq_key_table_lock, flags);
 	/*
 	 * Raise the apparent loglevel to maximum so that the sysrq header
@@ -542,6 +544,7 @@ void __handle_sysrq(int key, bool check_
 		console_loglevel = orig_log_level;
 	}
 	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
+oops_in_progress = save_oops_in_progress;
 }
 
 void handle_sysrq(int key)