I believe this was originally done by Dipankar Sarma. I pulled these
changes from the -rt kernel.

For better preformance, RCU should use a softirq instead of a
tasklet.

Signed-off-by: Steven Rostedt <[EMAIL PROTECTED]>

Index: linux-2.6-test/include/linux/interrupt.h
===================================================================
--- linux-2.6-test.orig/include/linux/interrupt.h
+++ linux-2.6-test/include/linux/interrupt.h
@@ -245,6 +245,9 @@ enum
 #ifdef CONFIG_HIGH_RES_TIMERS
        HRTIMER_SOFTIRQ,
 #endif
+       RCU_SOFTIRQ,    /* Preferable RCU should always be the last softirq */
+       /* Entries after this are ignored in split softirq mode */
+       MAX_SOFTIRQ,
 };
 
 /* softirq mask and active fields moved to irq_cpustat_t in
Index: linux-2.6-test/kernel/rcupdate.c
===================================================================
--- linux-2.6-test.orig/kernel/rcupdate.c
+++ linux-2.6-test/kernel/rcupdate.c
@@ -67,7 +67,6 @@ DEFINE_PER_CPU(struct rcu_data, rcu_data
 DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
 
 /* Fake initialization required by compiler */
-static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
 static int blimit = 10;
 static int qhimark = 10000;
 static int qlowmark = 100;
@@ -253,7 +252,7 @@ static void rcu_do_batch(struct rcu_data
        if (!rdp->donelist)
                rdp->donetail = &rdp->donelist;
        else
-               tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
+               raise_softirq(RCU_SOFTIRQ);
 }
 
 /*
@@ -405,7 +404,6 @@ static void rcu_offline_cpu(int cpu)
                                        &per_cpu(rcu_bh_data, cpu));
        put_cpu_var(rcu_data);
        put_cpu_var(rcu_bh_data);
-       tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
 }
 
 #else
@@ -417,7 +415,7 @@ static void rcu_offline_cpu(int cpu)
 #endif
 
 /*
- * This does the RCU processing work from tasklet context. 
+ * This does the RCU processing work from softirq context.
  */
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
                                        struct rcu_data *rdp)
@@ -462,7 +460,7 @@ static void __rcu_process_callbacks(stru
                rcu_do_batch(rdp);
 }
 
-static void rcu_process_callbacks(unsigned long unused)
+static void rcu_process_callbacks(struct softirq_action *unused)
 {
        __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
        __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
@@ -526,7 +524,7 @@ void rcu_check_callbacks(int cpu, int us
                rcu_bh_qsctr_inc(cpu);
        } else if (!in_softirq())
                rcu_bh_qsctr_inc(cpu);
-       tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
+       raise_softirq(RCU_SOFTIRQ);
 }
 
 static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
@@ -549,7 +547,7 @@ static void __devinit rcu_online_cpu(int
 
        rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
        rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
-       tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
+       open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
 }
 
 static int __cpuinit rcu_cpu_notify(struct notifier_block *self,

-- 
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