[MODERATED] [PATCH v4 19/28] MDSv4 14

[Andi Kleen <andi@firstfloor.org>]

By default we assume tasklets might touch user data and schedule
a cpu clear on next kernel exit.

Add new interfaces to allow audited tasklets to opt-out.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 include/linux/interrupt.h | 16 +++++++++++++++-
 kernel/softirq.c          | 25 +++++++++++++++++++------
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 291b7fee3afe..81b852fb5ecf 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -571,11 +571,22 @@ struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(0), func, data }
 #define DECLARE_TASKLET_DISABLED(name, func, data) \
 struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(1), func, data }
 
+#define DECLARE_TASKLET_NOUSER(name, func, data) \
+struct tasklet_struct name = { NULL, TASKLET_NO_USER, ATOMIC_INIT(0), func, data }
+
+#define DECLARE_TASKLET_DISABLED_NOUSER(name, func, data) \
+struct tasklet_struct name = { NULL, TASKLET_NO_USER, ATOMIC_INIT(1), func, data }
 
 enum
 {
 	TASKLET_STATE_SCHED,	/* Tasklet is scheduled for execution */
-	TASKLET_STATE_RUN	/* Tasklet is running (SMP only) */
+	TASKLET_STATE_RUN,	/* Tasklet is running (SMP only) */
+
+	/*
+	 * Set this flag when the tasklet is known to not touch user data,
+	 * so doesn't need extra CPU state clearing.
+	 */
+	TASKLET_NO_USER		= 1 << 5,
 };
 
 #ifdef CONFIG_SMP
@@ -639,6 +650,9 @@ extern void tasklet_kill(struct tasklet_struct *t);
 extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
 extern void tasklet_init(struct tasklet_struct *t,
 			 void (*func)(unsigned long), unsigned long data);
+extern void tasklet_init_flags(struct tasklet_struct *t,
+			 void (*func)(unsigned long), unsigned long data,
+			 unsigned flags);
 
 struct tasklet_hrtimer {
 	struct hrtimer		timer;
diff --git a/kernel/softirq.c b/kernel/softirq.c
index d28813306b2c..fdd4e3be3db7 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -26,6 +26,7 @@
 #include <linux/smpboot.h>
 #include <linux/tick.h>
 #include <linux/irq.h>
+#include <linux/clearcpu.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/irq.h>
@@ -522,6 +523,8 @@ static void tasklet_action_common(struct softirq_action *a,
 					BUG();
 				t->func(t->data);
 				tasklet_unlock(t);
+				if (!(t->state & TASKLET_NO_USER))
+					lazy_clear_cpu();
 				continue;
 			}
 			tasklet_unlock(t);
@@ -546,15 +549,23 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
 	tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
 }
 
-void tasklet_init(struct tasklet_struct *t,
-		  void (*func)(unsigned long), unsigned long data)
+void tasklet_init_flags(struct tasklet_struct *t,
+		  void (*func)(unsigned long), unsigned long data,
+		  unsigned flags)
 {
 	t->next = NULL;
-	t->state = 0;
+	t->state = flags;
 	atomic_set(&t->count, 0);
 	t->func = func;
 	t->data = data;
 }
+EXPORT_SYMBOL(tasklet_init_flags);
+
+void tasklet_init(struct tasklet_struct *t,
+		  void (*func)(unsigned long), unsigned long data)
+{
+	tasklet_init_flags(t, func, data, 0);
+}
 EXPORT_SYMBOL(tasklet_init);
 
 void tasklet_kill(struct tasklet_struct *t)
@@ -609,7 +620,8 @@ static void __tasklet_hrtimer_trampoline(unsigned long data)
  * @ttimer:	 tasklet_hrtimer which is initialized
  * @function:	 hrtimer callback function which gets called from softirq context
  * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
- * @mode:	 hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
+ * @mode:	 hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL),
+ *		 HRTIMER_MODE_NO_USER
  */
 void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
 			  enum hrtimer_restart (*function)(struct hrtimer *),
@@ -617,8 +629,9 @@ void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
 {
 	hrtimer_init(&ttimer->timer, which_clock, mode);
 	ttimer->timer.function = __hrtimer_tasklet_trampoline;
-	tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
-		     (unsigned long)ttimer);
+	tasklet_init_flags(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
+		     (unsigned long)ttimer,
+		     (mode & HRTIMER_MODE_NO_USER) ? TASKLET_NO_USER : 0);
 	ttimer->function = function;
 }
 EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
-- 
2.17.2