linux-kernel - [patch 03/14] tasklets: Provide tasklet_disable_in

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Message-Id: <20210309084241.563164193@linutronix.de>
Date:   Tue, 09 Mar 2021 09:42:06 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        ath9k-devel@....qualcomm.com, Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless@...r.kernel.org, Chas Williams <3chas3@...il.com>,
        linux-atm-general@...ts.sourceforge.net,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-hyperv@...r.kernel.org, linux-pci@...r.kernel.org,
        Stefan Richter <stefanr@...6.in-berlin.de>,
        linux1394-devel@...ts.sourceforge.net
Subject: [patch 03/14] 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>
---
 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);