[tip: irq/core] tasklets: Provide tasklet_disable_in_atomic()

tip-bot2 for Thomas Gleixner
2021-03-17T15:50:53Z

The following commit has been merged into the irq/core branch of tip:

Commit-ID: ca5f625118955fc544c3cb3dee7055d33ecadafb
Gitweb: https://git.kernel.org/tip/ca5f625118955fc544c3cb3dee7055d33ecadafb
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Tue, 09 Mar 2021 09:42:06 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 17 Mar 2021 16:33:52 +01:00

tasklets: Provide tasklet_disable_in_atomic()

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 <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210309084241.563164193@linutronix.de

---
include/linux/interrupt.h | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 0a4ce25..3c8a291 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -675,10 +675,21 @@ static inline void tasklet_unlock_wait(struct tasklet_struct *t)
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_nosync(struct tasklet_struct *t)
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);