rt-patches/0109-softirq-Check-preemption-after-reenabling-interrupts.patch

   1 From f3697f0972f10a5c91aefa7f48cbc6a66388610d Mon Sep 17 00:00:00 2001
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Sun, 13 Nov 2011 17:17:09 +0100
   4 Subject: [PATCH 109/366] softirq: Check preemption after reenabling interrupts
   5
   6 raise_softirq_irqoff() disables interrupts and wakes the softirq
   7 daemon, but after reenabling interrupts there is no preemption check,
   8 so the execution of the softirq thread might be delayed arbitrarily.
   9
  10 In principle we could add that check to local_irq_enable/restore, but
  11 that's overkill as the rasie_softirq_irqoff() sections are the only
  12 ones which show this behaviour.
  13
  14 Reported-by: Carsten Emde <cbe@osadl.org>
  15 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  16 ---
  17  block/blk-iopoll.c      | 3 +++
  18  block/blk-softirq.c     | 3 +++
  19  include/linux/preempt.h | 3 +++
  20  net/core/dev.c          | 7 +++++++
  21  4 files changed, 16 insertions(+)
  22
  23 diff --git a/block/blk-iopoll.c b/block/blk-iopoll.c
  24 index 0736729..3e21e31 100644
  25 --- a/block/blk-iopoll.c
  26 +++ b/block/blk-iopoll.c
  27 @@ -35,6 +35,7 @@ void blk_iopoll_sched(struct blk_iopoll *iop)
  28         list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
  29         __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
  30         local_irq_restore(flags);
  31 +       preempt_check_resched_rt();
  32  }
  33  EXPORT_SYMBOL(blk_iopoll_sched);
  34
  35 @@ -132,6 +133,7 @@ static void blk_iopoll_softirq(struct softirq_action *h)
  36                 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
  37
  38         local_irq_enable();
  39 +       preempt_check_resched_rt();
  40  }
  41
  42  /**
  43 @@ -201,6 +203,7 @@ static int blk_iopoll_cpu_notify(struct notifier_block *self,
  44                                  this_cpu_ptr(&blk_cpu_iopoll));
  45                 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
  46                 local_irq_enable();
  47 +               preempt_check_resched_rt();
  48         }
  49
  50         return NOTIFY_OK;
  51 diff --git a/block/blk-softirq.c b/block/blk-softirq.c
  52 index 53b1737..81c3c0a 100644
  53 --- a/block/blk-softirq.c
  54 +++ b/block/blk-softirq.c
  55 @@ -51,6 +51,7 @@ static void trigger_softirq(void *data)
  56                 raise_softirq_irqoff(BLOCK_SOFTIRQ);
  57
  58         local_irq_restore(flags);
  59 +       preempt_check_resched_rt();
  60  }
  61
  62  /*
  63 @@ -93,6 +94,7 @@ static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
  64                                  this_cpu_ptr(&blk_cpu_done));
  65                 raise_softirq_irqoff(BLOCK_SOFTIRQ);
  66                 local_irq_enable();
  67 +               preempt_check_resched_rt();
  68         }
  69
  70         return NOTIFY_OK;
  71 @@ -150,6 +152,7 @@ do_local:
  72                 goto do_local;
  73
  74         local_irq_restore(flags);
  75 +       preempt_check_resched_rt();
  76  }
  77
  78  /**
  79 diff --git a/include/linux/preempt.h b/include/linux/preempt.h
  80 index 210bd26..2b761d0 100644
  81 --- a/include/linux/preempt.h
  82 +++ b/include/linux/preempt.h
  83 @@ -160,8 +160,10 @@ do { \
  84
  85  #ifdef CONFIG_PREEMPT_RT_BASE
  86  # define preempt_enable_no_resched() sched_preempt_enable_no_resched()
  87 +# define preempt_check_resched_rt() preempt_check_resched()
  88  #else
  89  # define preempt_enable_no_resched() preempt_enable()
  90 +# define preempt_check_resched_rt() barrier();
  91  #endif
  92
  93  #define preemptible()  (preempt_count() == 0 && !irqs_disabled())
  94 @@ -232,6 +234,7 @@ do { \
  95  #define preempt_disable_notrace()              barrier()
  96  #define preempt_enable_no_resched_notrace()    barrier()
  97  #define preempt_enable_notrace()               barrier()
  98 +#define preempt_check_resched_rt()             barrier()
  99  #define preemptible()                          0
 100
 101  #endif /* CONFIG_PREEMPT_COUNT */
 102 diff --git a/net/core/dev.c b/net/core/dev.c
 103 index 145731a..98997de 100644
 104 --- a/net/core/dev.c
 105 +++ b/net/core/dev.c
 106 @@ -2246,6 +2246,7 @@ static inline void __netif_reschedule(struct Qdisc *q)
 107         sd->output_queue_tailp = &q->next_sched;
 108         raise_softirq_irqoff(NET_TX_SOFTIRQ);
 109         local_irq_restore(flags);
 110 +       preempt_check_resched_rt();
 111  }
 112
 113  void __netif_schedule(struct Qdisc *q)
 114 @@ -2327,6 +2328,7 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
 115         __this_cpu_write(softnet_data.completion_queue, skb);
 116         raise_softirq_irqoff(NET_TX_SOFTIRQ);
 117         local_irq_restore(flags);
 118 +       preempt_check_resched_rt();
 119  }
 120  EXPORT_SYMBOL(__dev_kfree_skb_irq);
 121
 122 @@ -3525,6 +3527,7 @@ drop:
 123         rps_unlock(sd);
 124
 125         local_irq_restore(flags);
 126 +       preempt_check_resched_rt();
 127
 128         atomic_long_inc(&skb->dev->rx_dropped);
 129         kfree_skb(skb);
 130 @@ -4535,6 +4538,7 @@ static void net_rps_action_and_irq_enable(struct softnet_data *sd)
 131                 sd->rps_ipi_list = NULL;
 132
 133                 local_irq_enable();
 134 +               preempt_check_resched_rt();
 135
 136                 /* Send pending IPI's to kick RPS processing on remote cpus. */
 137                 while (remsd) {
 138 @@ -4548,6 +4552,7 @@ static void net_rps_action_and_irq_enable(struct softnet_data *sd)
 139         } else
 140  #endif
 141                 local_irq_enable();
 142 +       preempt_check_resched_rt();
 143  }
 144
 145  static bool sd_has_rps_ipi_waiting(struct softnet_data *sd)
 146 @@ -4629,6 +4634,7 @@ void __napi_schedule(struct napi_struct *n)
 147         local_irq_save(flags);
 148         ____napi_schedule(this_cpu_ptr(&softnet_data), n);
 149         local_irq_restore(flags);
 150 +       preempt_check_resched_rt();
 151  }
 152  EXPORT_SYMBOL(__napi_schedule);
 153
 154 @@ -7485,6 +7491,7 @@ static int dev_cpu_callback(struct notifier_block *nfb,
 155
 156         raise_softirq_irqoff(NET_TX_SOFTIRQ);
 157         local_irq_enable();
 158 +       preempt_check_resched_rt();
 159
 160         /* Process offline CPU's input_pkt_queue */
 161         while ((skb = __skb_dequeue(&oldsd->process_queue))) {
 162 --
 163 1.9.1
 164