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[Xen-devel] [RFC PATCH v1 5/5] tasklet: Remove the scaffolding.



To catch any bisection issues, we had been replacing parts of
the tasklet code one functionality on top of each other. Now
that all of it is per-cpu and working we can remove the
old scaffolding and collapse functions.

We also remove the 'is_percpu' flag that is not needed
anymore. Most of this is code deletion and code
motion. No new functionality is added.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 xen/common/tasklet.c      | 110 ++++++++++++++++++----------------------------
 xen/include/xen/tasklet.h |   9 ++--
 2 files changed, 46 insertions(+), 73 deletions(-)

diff --git a/xen/common/tasklet.c b/xen/common/tasklet.c
index 618e73b..192fa79 100644
--- a/xen/common/tasklet.c
+++ b/xen/common/tasklet.c
@@ -49,7 +49,6 @@ static void percpu_tasklet_feed(void *arg)
     while ( !list_empty(list) )
     {
         t = list_entry(list->next, struct tasklet, list);
-        BUG_ON(!t->is_percpu);
         list_del(&t->list);
 
         if ( t->is_softirq )
@@ -76,59 +75,44 @@ out:
 static void tasklet_enqueue(struct tasklet *t)
 {
     unsigned int cpu = t->scheduled_on;
+    unsigned long flags;
+    struct list_head *list;
 
-    if ( t->is_percpu )
-    {
-        unsigned long flags;
-        struct list_head *list;
-
-        INIT_LIST_HEAD(&t->list);
-
-        if ( cpu != smp_processor_id() )
-        {
-            spin_lock_irqsave(&feeder_lock, flags);
-
-            list = &per_cpu(tasklet_feeder, cpu);
-            list_add_tail(&t->list, list);
-
-            spin_unlock_irqrestore(&feeder_lock, flags);
-            on_selected_cpus(cpumask_of(cpu), percpu_tasklet_feed, NULL, 1);
-            return;
-        }
-        if ( t->is_softirq )
-        {
-
-            local_irq_save(flags);
-
-            list = &__get_cpu_var(softirq_list);
-            list_add_tail(&t->list, list);
-            raise_softirq(TASKLET_SOFTIRQ);
+    INIT_LIST_HEAD(&t->list);
 
-            local_irq_restore(flags);
-            return;
-        }
-        else
-        {
-            unsigned long *work_to_do = &__get_cpu_var(tasklet_work_to_do);
+    if ( cpu != smp_processor_id() )
+    {
+        spin_lock_irqsave(&feeder_lock, flags);
 
-            local_irq_save(flags);
+        list = &per_cpu(tasklet_feeder, cpu);
+        list_add_tail(&t->list, list);
 
-            list = &__get_cpu_var(tasklet_list);
-            list_add_tail(&t->list, list);
-            if ( !test_and_set_bit(_TASKLET_enqueued, work_to_do) )
-                raise_softirq(SCHEDULE_SOFTIRQ);
+        spin_unlock_irqrestore(&feeder_lock, flags);
+        on_selected_cpus(cpumask_of(cpu), percpu_tasklet_feed, NULL, 1);
+        return;
+     }
+     if ( t->is_softirq )
+     {
+         local_irq_save(flags);
+
+         list = &__get_cpu_var(softirq_list);
+         list_add_tail(&t->list, list);
+         raise_softirq(TASKLET_SOFTIRQ);
+
+         local_irq_restore(flags);
+     }
+     else
+     {
+          unsigned long *work_to_do = &__get_cpu_var(tasklet_work_to_do);
+
+          local_irq_save(flags);
+
+          list = &__get_cpu_var(tasklet_list);
+          list_add_tail(&t->list, list);
+          if ( !test_and_set_bit(_TASKLET_enqueued, work_to_do) )
+            raise_softirq(SCHEDULE_SOFTIRQ);
 
-            local_irq_restore(flags);
-            return;
-        }
-    }
-    if ( t->is_softirq )
-    {
-        BUG();
-    }
-    else
-    {
-        BUG();
+          local_irq_restore(flags);
     }
 }
 
@@ -137,16 +121,11 @@ void tasklet_schedule_on_cpu(struct tasklet *t, unsigned 
int cpu)
     if ( !tasklets_initialised || t->is_dead )
         return;
 
-    if ( t->is_percpu )
+    if ( !test_and_set_bit(TASKLET_STATE_SCHED, &t->state) )
     {
-        if ( !test_and_set_bit(TASKLET_STATE_SCHED, &t->state) )
-        {
-            t->scheduled_on = cpu;
-            tasklet_enqueue(t);
-        }
-        return;
+        t->scheduled_on = cpu;
+        tasklet_enqueue(t);
     }
-    BUG();
 }
 
 void tasklet_schedule(struct tasklet *t)
@@ -306,19 +285,15 @@ static void tasklet_softirq_action(void)
 
 void tasklet_kill(struct tasklet *t)
 {
-    if ( t->is_percpu )
+    while ( test_and_set_bit(TASKLET_STATE_SCHED, &t->state) )
     {
-        while ( test_and_set_bit(TASKLET_STATE_SCHED, &t->state) )
-        {
-            do {
+        do {
                 process_pending_softirqs();
-            } while ( test_bit(TASKLET_STATE_SCHED, &t->state) );
-        }
-        tasklet_unlock_wait(t);
-        clear_bit(TASKLET_STATE_SCHED, &t->state);
-        t->is_dead = 1;
-        return;
+        } while ( test_bit(TASKLET_STATE_SCHED, &t->state) );
     }
+    tasklet_unlock_wait(t);
+    clear_bit(TASKLET_STATE_SCHED, &t->state);
+    t->is_dead = 1;
 }
 
 static void migrate_tasklets_from_cpu(unsigned int cpu, struct list_head *list)
@@ -348,7 +323,6 @@ void tasklet_init(
     t->scheduled_on = -1;
     t->func = func;
     t->data = data;
-    t->is_percpu = 1;
 }
 
 void softirq_tasklet_init(
diff --git a/xen/include/xen/tasklet.h b/xen/include/xen/tasklet.h
index 21efe7b..b7a6a81 100644
--- a/xen/include/xen/tasklet.h
+++ b/xen/include/xen/tasklet.h
@@ -22,19 +22,18 @@ struct tasklet
     bool_t is_softirq;
     bool_t is_running;
     bool_t is_dead;
-    bool_t is_percpu;
     void (*func)(unsigned long);
     unsigned long data;
 };
 
-#define _DECLARE_TASKLET(name, func, data, softirq, percpu)             \
+#define _DECLARE_TASKLET(name, func, data, softirq)                     \
     struct tasklet name = {                                             \
-        LIST_HEAD_INIT(name.list), 0, -1, softirq, 0, 0, percpu,        \
+        LIST_HEAD_INIT(name.list), 0, -1, softirq, 0, 0,                \
         func, data }
 #define DECLARE_TASKLET(name, func, data)               \
-    _DECLARE_TASKLET(name, func, data, 0, 0)
+    _DECLARE_TASKLET(name, func, data, 0)
 #define DECLARE_SOFTIRQ_TASKLET(name, func, data)       \
-    _DECLARE_TASKLET(name, func, data, 1, 1)
+    _DECLARE_TASKLET(name, func, data, 1)
 
 /* Indicates status of tasklet work on each CPU. */
 DECLARE_PER_CPU(unsigned long, tasklet_work_to_do);
-- 
1.9.3


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