[patch 03/14] tasklets: Provide tasklet_disable_in_atomic()

[Thomas Gleixner]

Replacing the spin wait loops in tasklet_unlock_wait() with
wait_var_event() is not possible as a handful of tasklet_disable()
invocations are happening in atomic context. All other invocations are in
teardown paths which can sleep.

Provide tasklet_disable_in_atomic() and tasklet_unlock_spin_wait() to
convert the few atomic use cases over, which allows to change
tasklet_disable() and tasklet_unlock_wait() in a later step.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 include/linux/interrupt.h |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -675,10 +675,21 @@ static inline void tasklet_unlock_wait(s
        while (test_bit(TASKLET_STATE_RUN, &t->state))
                cpu_relax();
 }
+
+/*
+ * Do not use in new code. Waiting for tasklets from atomic contexts is
+ * error prone and should be avoided.
+ */
+static inline void tasklet_unlock_spin_wait(struct tasklet_struct *t)
+{
+       while (test_bit(TASKLET_STATE_RUN, &t->state))
+               cpu_relax();
+}
 #else
 static inline int tasklet_trylock(struct tasklet_struct *t) { return 1; }
 static inline void tasklet_unlock(struct tasklet_struct *t) { }
 static inline void tasklet_unlock_wait(struct tasklet_struct *t) { }
+static inline void tasklet_unlock_spin_wait(struct tasklet_struct *t) { }
 #endif
 
 extern void __tasklet_schedule(struct tasklet_struct *t);
@@ -703,6 +714,17 @@ static inline void tasklet_disable_nosyn
        smp_mb__after_atomic();
 }
 
+/*
+ * Do not use in new code. Disabling tasklets from atomic contexts is
+ * error prone and should be avoided.
+ */
+static inline void tasklet_disable_in_atomic(struct tasklet_struct *t)
+{
+       tasklet_disable_nosync(t);
+       tasklet_unlock_spin_wait(t);
+       smp_mb();
+}
+
 static inline void tasklet_disable(struct tasklet_struct *t)
 {
        tasklet_disable_nosync(t);