revert "softirq: Add support for triggering softirq work on softirqs"

This commit was incomplete in that code to remove items from the per-cpu
lists was missing and never acquired a user in the 5 years it has been in
the tree.  We're going to implement what it seems to try to archive in a
simpler way, and this code is in the way of doing so.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index c9e831d..db43b58 100644 (file)
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -11,8 +11,6 @@
 #include <linux/irqnr.h>
 #include <linux/hardirq.h>
 #include <linux/irqflags.h>
-#include <linux/smp.h>
-#include <linux/percpu.h>
 #include <linux/hrtimer.h>
 #include <linux/kref.h>
 #include <linux/workqueue.h>
@@ -392,15 +390,6 @@ extern void __raise_softirq_irqoff(unsigned int nr);
 extern void raise_softirq_irqoff(unsigned int nr);
 extern void raise_softirq(unsigned int nr);
 
-/* This is the worklist that queues up per-cpu softirq work.
- *
- * send_remote_sendirq() adds work to these lists, and
- * the softirq handler itself dequeues from them.  The queues
- * are protected by disabling local cpu interrupts and they must
- * only be accessed by the local cpu that they are for.
- */
-DECLARE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list);
-
 DECLARE_PER_CPU(struct task_struct *, ksoftirqd);
 
 static inline struct task_struct *this_cpu_ksoftirqd(void)
@@ -408,17 +397,6 @@ static inline struct task_struct *this_cpu_ksoftirqd(void)
        return this_cpu_read(ksoftirqd);
 }
 
-/* Try to send a softirq to a remote cpu.  If this cannot be done, the
- * work will be queued to the local cpu.
- */
-extern void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq);
-
-/* Like send_remote_softirq(), but the caller must disable local cpu interrupts
- * and compute the current cpu, passed in as 'this_cpu'.
- */
-extern void __send_remote_softirq(struct call_single_data *cp, int cpu,
-                                 int this_cpu, int softirq);
-
 /* Tasklets --- multithreaded analogue of BHs.
 
    Main feature differing them of generic softirqs: tasklet

diff --git a/kernel/softirq.c b/kernel/softirq.c
index b249883..11025cc 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -6,8 +6,6 @@
  *     Distribute under GPLv2.
  *
  *     Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
- *
- *     Remote softirq infrastructure is by Jens Axboe.
  */
 
 #include <linux/export.h>
@@ -627,146 +625,17 @@ void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
 }
 EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
 
-/*
- * Remote softirq bits
- */
-
-DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list);
-EXPORT_PER_CPU_SYMBOL(softirq_work_list);
-
-static void __local_trigger(struct call_single_data *cp, int softirq)
-{
-       struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]);
-
-       list_add_tail(&cp->list, head);
-
-       /* Trigger the softirq only if the list was previously empty.  */
-       if (head->next == &cp->list)
-               raise_softirq_irqoff(softirq);
-}
-
-#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
-static void remote_softirq_receive(void *data)
-{
-       struct call_single_data *cp = data;
-       unsigned long flags;
-       int softirq;
-
-       softirq = *(int *)cp->info;
-       local_irq_save(flags);
-       __local_trigger(cp, softirq);
-       local_irq_restore(flags);
-}
-
-static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
-{
-       if (cpu_online(cpu)) {
-               cp->func = remote_softirq_receive;
-               cp->info = &softirq;
-               cp->flags = 0;
-
-               __smp_call_function_single(cpu, cp, 0);
-               return 0;
-       }
-       return 1;
-}
-#else /* CONFIG_USE_GENERIC_SMP_HELPERS */
-static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
-{
-       return 1;
-}
-#endif
-
-/**
- * __send_remote_softirq - try to schedule softirq work on a remote cpu
- * @cp: private SMP call function data area
- * @cpu: the remote cpu
- * @this_cpu: the currently executing cpu
- * @softirq: the softirq for the work
- *
- * Attempt to schedule softirq work on a remote cpu.  If this cannot be
- * done, the work is instead queued up on the local cpu.
- *
- * Interrupts must be disabled.
- */
-void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq)
-{
-       if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq))
-               __local_trigger(cp, softirq);
-}
-EXPORT_SYMBOL(__send_remote_softirq);
-
-/**
- * send_remote_softirq - try to schedule softirq work on a remote cpu
- * @cp: private SMP call function data area
- * @cpu: the remote cpu
- * @softirq: the softirq for the work
- *
- * Like __send_remote_softirq except that disabling interrupts and
- * computing the current cpu is done for the caller.
- */
-void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
-{
-       unsigned long flags;
-       int this_cpu;
-
-       local_irq_save(flags);
-       this_cpu = smp_processor_id();
-       __send_remote_softirq(cp, cpu, this_cpu, softirq);
-       local_irq_restore(flags);
-}
-EXPORT_SYMBOL(send_remote_softirq);
-
-static int remote_softirq_cpu_notify(struct notifier_block *self,
-                                              unsigned long action, void *hcpu)
-{
-       /*
-        * If a CPU goes away, splice its entries to the current CPU
-        * and trigger a run of the softirq
-        */
-       if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
-               int cpu = (unsigned long) hcpu;
-               int i;
-
-               local_irq_disable();
-               for (i = 0; i < NR_SOFTIRQS; i++) {
-                       struct list_head *head = &per_cpu(softirq_work_list[i], cpu);
-                       struct list_head *local_head;
-
-                       if (list_empty(head))
-                               continue;
-
-                       local_head = &__get_cpu_var(softirq_work_list[i]);
-                       list_splice_init(head, local_head);
-                       raise_softirq_irqoff(i);
-               }
-               local_irq_enable();
-       }
-
-       return NOTIFY_OK;
-}
-
-static struct notifier_block remote_softirq_cpu_notifier = {
-       .notifier_call  = remote_softirq_cpu_notify,
-};
-
 void __init softirq_init(void)
 {
        int cpu;
 
        for_each_possible_cpu(cpu) {
-               int i;
-
                per_cpu(tasklet_vec, cpu).tail =
                        &per_cpu(tasklet_vec, cpu).head;
                per_cpu(tasklet_hi_vec, cpu).tail =
                        &per_cpu(tasklet_hi_vec, cpu).head;
-               for (i = 0; i < NR_SOFTIRQS; i++)
-                       INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu));
        }
 
-       register_hotcpu_notifier(&remote_softirq_cpu_notifier);
-
        open_softirq(TASKLET_SOFTIRQ, tasklet_action);
        open_softirq(HI_SOFTIRQ, tasklet_hi_action);
 }