preempt-rt: allow immediate Magic SysRq output for PREEMPT_RT_FULL

Index: b/drivers/tty/sysrq.c
===================================================================
@@ -492,6 +492,23 @@ static void __sysrq_put_key_op(int key, 
                 sysrq_key_table[i] = op_p;
 }
 
+#ifdef CONFIG_MAGIC_SYSRQ_FORCE_PRINTK
+
+int sysrq_in_progress;
+
+static void set_sysrq_in_progress(int value)
+{
+	sysrq_in_progress = value;
+}
+
+#else
+
+static void set_sysrq_in_progress(int value)
+{
+}
+
+#endif
+
 void __handle_sysrq(int key, bool check_mask)
 {
 	struct sysrq_key_op *op_p;

@@ -500,6 +517,9 @@ void __handle_sysrq(int key, bool check_
 	unsigned long flags;
 
 	spin_lock_irqsave(&sysrq_key_table_lock, flags);
+
+	set_sysrq_in_progress(1);
+
 	/*
 	 * Raise the apparent loglevel to maximum so that the sysrq header
 	 * is shown to provide the user with positive feedback.  We do not

@@ -541,6 +561,9 @@ void __handle_sysrq(int key, bool check_
 		printk("\n");
 		console_loglevel = orig_log_level;
 	}
+
+	set_sysrq_in_progress(0);
+
 	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 }
 

Index: b/include/linux/kernel.h
===================================================================
@@ -327,6 +327,11 @@ unsigned long int_sqrt(unsigned long);
 extern void bust_spinlocks(int yes);
 extern void wake_up_klogd(void);
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */
+#ifdef CONFIG_MAGIC_SYSRQ_FORCE_PRINTK
+extern int sysrq_in_progress;
+#else
+#define sysrq_in_progress 0
+#endif
 extern int panic_timeout;
 extern int panic_on_oops;
 extern int panic_on_unrecovered_nmi;

Index: b/kernel/printk.c
===================================================================
@@ -831,8 +831,8 @@ 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 = (!early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
+		!preempt_count()) || sysrq_in_progress;
 #else
 	int lock = 1;
 #endif

Index: b/drivers/tty/serial/bcm63xx_uart.c
===================================================================
@@ -722,7 +722,7 @@ static void bcm_console_write(struct con
 	if (port->sysrq) {
 		/* bcm_uart_interrupt() already took the lock */
 		locked = 0;
-	} else if (oops_in_progress) {
+	} else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&port->lock);
 	} else {
 		spin_lock(&port->lock);

Index: b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
===================================================================
@@ -1225,7 +1225,7 @@ static void cpm_uart_console_write(struc
 {
 	struct uart_cpm_port *pinfo = &cpm_uart_ports[co->index];
 	unsigned long flags;
-	int nolock = oops_in_progress;
+	int nolock = oops_in_progress || sysrq_in_progress;
 
 	if (unlikely(nolock)) {
 		local_irq_save(flags);

Index: b/drivers/tty/serial/mfd.c
===================================================================
@@ -1118,7 +1118,7 @@ serial_hsu_console_write(struct console 
 	local_irq_save(flags);
 	if (up->port.sysrq)
 		locked = 0;
-	else if (oops_in_progress) {
+	else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&up->port.lock);
 	} else
 		spin_lock(&up->port.lock);

Index: b/drivers/tty/serial/nwpserial.c
===================================================================
@@ -70,7 +70,7 @@ nwpserial_console_write(struct console *
 	unsigned long flags;
 	int locked = 1;
 
-	if (oops_in_progress)
+	if (oops_in_progress || sysrq_in_progress)
 		locked = spin_trylock_irqsave(&up->port.lock, flags);
 	else
 		spin_lock_irqsave(&up->port.lock, flags);

Index: b/drivers/tty/serial/omap-serial.c
===================================================================
@@ -949,7 +949,7 @@ serial_omap_console_write(struct console
 
 	if (up->port.sysrq)
 		locked = 0;
-	else if (oops_in_progress)
+	else if (oops_in_progress || sysrq_in_progress)
 		locked = spin_trylock_irqsave(&up->port.lock, flags);
 	else
 		spin_lock_irqsave(&up->port.lock, flags);

Index: b/drivers/tty/serial/sunhv.c
===================================================================
@@ -435,7 +435,7 @@ static void sunhv_console_write_paged(st
 	local_irq_save(flags);
 	if (port->sysrq) {
 		locked = 0;
-	} else if (oops_in_progress) {
+	} else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&port->lock);
 	} else
 		spin_lock(&port->lock);

@@ -494,7 +494,7 @@ static void sunhv_console_write_bychar(s
 	local_irq_save(flags);
 	if (port->sysrq) {
 		locked = 0;
-	} else if (oops_in_progress) {
+	} else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&port->lock);
 	} else
 		spin_lock(&port->lock);

Index: b/drivers/tty/serial/sunsab.c
===================================================================
@@ -852,7 +852,7 @@ static void sunsab_console_write(struct 
 	local_irq_save(flags);
 	if (up->port.sysrq) {
 		locked = 0;
-	} else if (oops_in_progress) {
+	} else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&up->port.lock);
 	} else
 		spin_lock(&up->port.lock);

Index: b/drivers/tty/serial/sunsu.c
===================================================================
@@ -1297,7 +1297,7 @@ static void sunsu_console_write(struct c
 	local_irq_save(flags);
 	if (up->port.sysrq) {
 		locked = 0;
-	} else if (oops_in_progress) {
+	} else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&up->port.lock);
 	} else
 		spin_lock(&up->port.lock);

Index: b/drivers/tty/serial/sunzilog.c
===================================================================
@@ -1204,7 +1204,7 @@ sunzilog_console_write(struct console *c
 	local_irq_save(flags);
 	if (up->port.sysrq) {
 		locked = 0;
-	} else if (oops_in_progress) {
+	} else if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock(&up->port.lock);
 	} else
 		spin_lock(&up->port.lock);

Index: b/drivers/tty/serial/uartlite.c
===================================================================
@@ -387,7 +387,7 @@ static void ulite_console_write(struct c
 	unsigned int ier;
 	int locked = 1;
 
-	if (oops_in_progress) {
+	if (oops_in_progress || sysrq_in_progress) {
 		locked = spin_trylock_irqsave(&port->lock, flags);
 	} else
 		spin_lock_irqsave(&port->lock, flags);

Index: b/drivers/tty/serial/xilinx_uartps.c
===================================================================
@@ -834,7 +834,7 @@ static void xuartps_console_write(struct
 	unsigned int imr;
 	int locked = 1;
 
-	if (oops_in_progress)
+	if (oops_in_progress || sysrq_in_progress)
 		locked = spin_trylock_irqsave(&port->lock, flags);
 	else
 		spin_lock_irqsave(&port->lock, flags);

Index: b/drivers/tty/serial/8250.c
===================================================================
@@ -2898,7 +2898,7 @@ serial8250_console_write(struct console 
 	if (unlikely(in_kdb_printk())) {
 		locked = 0;
 	} else {
-		if (up->port.sysrq || oops_in_progress)
+		if (up->port.sysrq || oops_in_progress || sysrq_in_progress)
 			locked = spin_trylock_irqsave(&up->port.lock, flags);
 		else
 			spin_lock_irqsave(&up->port.lock, flags);