Merge tag 'v3.18.11-rt7-lno1' of git://git.linaro.org/people/anders.roxell/linux-rt into linux-linaro-lsk-v3.18-rt

Linux 3.18.11-rt7

* tag 'v3.18.11-rt7-lno1' of git://git.linaro.org/people/anders.roxell/linux-rt: (2276 commits)
  localversion.patch
  workqueue: Prevent deadlock/stall on RT
  sched: Do not clear PF_NO_SETAFFINITY flag in select_fallback_rq()
  md: disable bcache
  rt,ntp: Move call to schedule_delayed_work() to helper thread
  scheduling while atomic in cgroup code
  cgroups: use simple wait in css_release()
  a few open coded completions
  completion: Use simple wait queues
  rcu-more-swait-conversions.patch
  kernel/treercu: use a simple waitqueue
  work-simple: Simple work queue implemenation
  simple-wait: rename and export the equivalent of waitqueue_active()
  wait-simple: Rework for use with completions
  wait-simple: Simple waitqueue implementation
  wait.h: include atomic.h
  drm/i915: drop trace_i915_gem_ring_dispatch on rt
  gpu/i915: don't open code these things
  mmc: sdhci: don't provide hard irq handler
  mmci: Remove bogus local_irq_save()
  ...

3 files changed, 26 insertions, 15 deletions

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index e5c31eadb0ac..dbd63ae2d079 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -37,6 +37,7 @@
 #include <linux/nmi.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/kdb.h>
 #include <linux/uaccess.h>
 #include <linux/pm_runtime.h>
 #ifdef CONFIG_SPARC
@@ -81,7 +82,16 @@ static unsigned int skip_txen_test; /* force skip of txen test at init time */
 #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)
 
@@ -3197,7 +3207,7 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
 
 	serial8250_rpm_get(up);
 
-	if (port->sysrq || oops_in_progress)
+	if (port->sysrq || oops_in_progress || in_kdb_printk())
 		locked = spin_trylock_irqsave(&port->lock, flags);
 	else
 		spin_lock_irqsave(&port->lock, flags);
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 02016fcd91b8..5ef2c62bb904 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1935,13 +1935,19 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
 
 	clk_enable(uap->clk);
 
-	local_irq_save(flags);
+	/*
+	 * local_irq_save(flags);
+	 *
+	 * This local_irq_save() is nonsense. If we come in via sysrq
+	 * handling then interrupts are already disabled. Aside of
+	 * that the port.sysrq check is racy on SMP regardless.
+	*/
 	if (uap->port.sysrq)
 		locked = 0;
 	else if (oops_in_progress)
-		locked = spin_trylock(&uap->port.lock);
+		locked = spin_trylock_irqsave(&uap->port.lock, flags);
 	else
-		spin_lock(&uap->port.lock);
+		spin_lock_irqsave(&uap->port.lock, flags);
 
 	/*
 	 *	First save the CR then disable the interrupts
@@ -1963,8 +1969,7 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
 	writew(old_cr, uap->port.membase + UART011_CR);
 
 	if (locked)
-		spin_unlock(&uap->port.lock);
-	local_irq_restore(flags);
+		spin_unlock_irqrestore(&uap->port.lock, flags);
 
 	clk_disable(uap->clk);
 }
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 18c30cabe27f..6f0629ead171 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1270,13 +1270,10 @@ serial_omap_console_write(struct console *co, const char *s,
 
 	pm_runtime_get_sync(up->dev);
 
-	local_irq_save(flags);
-	if (up->port.sysrq)
-		locked = 0;
-	else if (oops_in_progress)
-		locked = spin_trylock(&up->port.lock);
+	if (up->port.sysrq || oops_in_progress)
+		locked = spin_trylock_irqsave(&up->port.lock, flags);
 	else
-		spin_lock(&up->port.lock);
+		spin_lock_irqsave(&up->port.lock, flags);
 
 	/*
 	 * First save the IER then disable the interrupts
@@ -1305,8 +1302,7 @@ serial_omap_console_write(struct console *co, const char *s,
 	pm_runtime_mark_last_busy(up->dev);
 	pm_runtime_put_autosuspend(up->dev);
 	if (locked)
-		spin_unlock(&up->port.lock);
-	local_irq_restore(flags);
+		spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
 static int __init