linux-kernel - [PATCH RT] convert RCU Preempt tasklet into softirq.

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Message-Id: <1181240819.10408.14.camel@localhost.localdomain>
Date:	Thu, 07 Jun 2007 14:26:59 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	john stultz <johnstul@...ibm.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Oleg Nesterov <oleg@...sign.ru>,
	LKML <linux-kernel@...r.kernel.org>,
	Dipankar Sarma <dipankar@...ibm.com>,
	RT <linux-rt-users@...r.kernel.org>
Subject: [PATCH RT] convert RCU Preempt tasklet into softirq.

Following Dipankar's lead, I converted the tasklet in rcupreempt.c into
a softirq.

I've compiled and booted with this patch, but ran no other tests.

Paul,  I'm disappointed, this was so trivial I didn't get a chance to
learn anything ;-)


Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

Index: linux-2.6.21-rt9/include/linux/rcupreempt.h
===================================================================
--- linux-2.6.21-rt9.orig/include/linux/rcupreempt.h
+++ linux-2.6.21-rt9/include/linux/rcupreempt.h
@@ -63,7 +63,9 @@ extern void rcu_check_callbacks(int cpu,
 extern void rcu_restart_cpu(int cpu);
 extern long rcu_batches_completed(void);
 
-extern void rcu_process_callbacks(unsigned long unused);
+struct softirq_action;
+
+extern void rcu_process_callbacks(struct softirq_action *unused);
 
 #endif /* __KERNEL__ */
 #endif /* __LINUX_RCUPREEMPT_H */
Index: linux-2.6.21-rt9/kernel/rcupreempt.c
===================================================================
--- linux-2.6.21-rt9.orig/kernel/rcupreempt.c
+++ linux-2.6.21-rt9/kernel/rcupreempt.c
@@ -57,7 +57,6 @@
 struct rcu_data {
 	raw_spinlock_t	lock;
 	long		completed;	/* Number of last completed batch. */
-	struct tasklet_struct rcu_tasklet;
 	struct rcu_head *nextlist;
 	struct rcu_head **nexttail;
 	struct rcu_head *waitlist;
@@ -255,7 +254,7 @@ void rcu_check_callbacks(int cpu, int us
 		spin_unlock_irqrestore(&rcu_data.lock, oldirq);
 	} else {
 		spin_unlock_irqrestore(&rcu_data.lock, oldirq);
-		tasklet_schedule(&rcu_data.rcu_tasklet);
+		raise_softirq(RCU_SOFTIRQ);
 	}
 }
 
@@ -279,7 +278,7 @@ void rcu_advance_callbacks(int cpu, int 
 	spin_unlock_irqrestore(&rcu_data.lock, oldirq);
 }
 
-void rcu_process_callbacks(unsigned long unused)
+void rcu_process_callbacks(struct softirq_action *unused)
 {
 	unsigned long flags;
 	struct rcu_head *next, *list;
@@ -367,7 +366,7 @@ void __init __rcu_init(void)
 	rcu_data.waittail = &rcu_data.waitlist;
 	rcu_data.donelist = NULL;
 	rcu_data.donetail = &rcu_data.donelist;
-	tasklet_init(&rcu_data.rcu_tasklet, rcu_process_callbacks, 0UL);
+	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
 }
 
 /*


-
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