linux-kernel - [ANNOUNCE] 4.19.115-rt49

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Date:   Mon, 27 Apr 2020 14:30:18 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        John Kacur <jkacur@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Daniel Wagner <wagi@...om.org>,
        Clark Williams <williams@...hat.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: [ANNOUNCE] 4.19.115-rt49

Hello RT Folks!

I'm pleased to announce the 4.19.115-rt49 stable release.

You can get this release via the git tree at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

  branch: v4.19-rt
  Head SHA1: 7ef3100b1ce706450de2fa2b76003b1e47e12131

Or to build 4.19.115-rt49 directly, the following patches should be applied:

  https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.19.tar.xz

  https://www.kernel.org/pub/linux/kernel/v4.x/patch-4.19.115.xz

  https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/patch-4.19.115-rt49.patch.xz

You can also build from 4.19.115-rt48 by applying the incremental patch:

  https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/incr/patch-4.19.115-rt48-rt49.patch.xz

Enjoy!

   Tom

Changes from v4.19.115-rt48:
---

Tom Zanussi (1):
      Linux 4.19.115-rt49

Zhang Xiao (1):
      tasklet: Address a race resulting in double-enqueue
---
include/linux/interrupt.h | 5 ++++-
 kernel/softirq.c          | 6 +++++-
 localversion-rt           | 2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)
---
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 97d9ba26915e..a3b5edb26bc5 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -579,12 +579,15 @@ enum
 {
 	TASKLET_STATE_SCHED,	/* Tasklet is scheduled for execution */
 	TASKLET_STATE_RUN,	/* Tasklet is running (SMP only) */
-	TASKLET_STATE_PENDING	/* Tasklet is pending */
+	TASKLET_STATE_PENDING,	/* Tasklet is pending */
+	TASKLET_STATE_CHAINED	/* Tasklet is chained */
 };
 
 #define TASKLET_STATEF_SCHED	(1 << TASKLET_STATE_SCHED)
 #define TASKLET_STATEF_RUN	(1 << TASKLET_STATE_RUN)
 #define TASKLET_STATEF_PENDING	(1 << TASKLET_STATE_PENDING)
+#define TASKLET_STATEF_CHAINED	(1 << TASKLET_STATE_CHAINED)
+#define TASKLET_STATEF_RC	(TASKLET_STATEF_RUN | TASKLET_STATEF_CHAINED)
 
 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
 static inline int tasklet_trylock(struct tasklet_struct *t)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 25bcf2f2714b..73dae64bfc9c 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -947,6 +947,10 @@ static void __tasklet_schedule_common(struct tasklet_struct *t,
 	 * is locked before adding it to the list.
 	 */
 	if (test_bit(TASKLET_STATE_SCHED, &t->state)) {
+		if (test_and_set_bit(TASKLET_STATE_CHAINED, &t->state)) {
+			tasklet_unlock(t);
+			return;
+		}
 		t->next = NULL;
 		*head->tail = t;
 		head->tail = &(t->next);
@@ -1040,7 +1044,7 @@ static void tasklet_action_common(struct softirq_action *a,
 again:
 		t->func(t->data);
 
-		while (!tasklet_tryunlock(t)) {
+		while (cmpxchg(&t->state, TASKLET_STATEF_RC, 0) != TASKLET_STATEF_RC) {
 			/*
 			 * If it got disabled meanwhile, bail out:
 			 */
diff --git a/localversion-rt b/localversion-rt
index 24707986c321..4b7dca68a5b4 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt48
+-rt49