linux-kernel - [tip: irq/core] tasklets: Provide tasklet_disable_in

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Date:   Wed, 17 Mar 2021 15:48:59 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, maz@...nel.org
Subject: [tip: irq/core] tasklets: Provide tasklet_disable_in_atomic()

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@...utronix.de>
AuthorDate:    Tue, 09 Mar 2021 09:42:06 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.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@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.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);