releases/3.18.49/net-pktgen-remove-rcu-locking-in-pktgen_change_name.patch

   1 From foo@baz Mon Feb 20 16:34:36 CET 2017
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Sat, 15 Oct 2016 17:50:49 +0200
   4 Subject: [PATCH 087/760] net: pktgen: remove rcu locking in pktgen_change_name()
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8
   9 [ Upstream commit 9a0b1e8ba4061778897b544afc898de2163382f7 ]
  10
  11 After Jesper commit back in linux-3.18, we trigger a lockdep
  12 splat in proc_create_data() while allocating memory from
  13 pktgen_change_name().
  14
  15 This patch converts t->if_lock to a mutex, since it is now only
  16 used from control path, and adds proper locking to pktgen_change_name()
  17
  18 1) pktgen_thread_lock to protect the outer loop (iterating threads)
  19 2) t->if_lock to protect the inner loop (iterating devices)
  20
  21 Note that before Jesper patch, pktgen_change_name() was lacking proper
  22 protection, but lockdep was not able to detect the problem.
  23
  24 Fixes: 8788370a1d4b ("pktgen: RCU-ify "if_list" to remove lock in next_to_run()")
  25 Reported-by: John Sperbeck <jsperbeck@google.com>
  26 Signed-off-by: Eric Dumazet <edumazet@google.com>
  27 Cc: Jesper Dangaard Brouer <brouer@redhat.com>
  28 Signed-off-by: David S. Miller <davem@davemloft.net>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  31 ---
  32  net/core/pktgen.c |   17 ++++++++++-------
  33  1 file changed, 10 insertions(+), 7 deletions(-)
  34
  35 --- a/net/core/pktgen.c
  36 +++ b/net/core/pktgen.c
  37 @@ -211,8 +211,8 @@
  38  #define T_REMDEV      (1<<3)   /* Remove one dev */
  39
  40  /* If lock -- protects updating of if_list */
  41 -#define   if_lock(t)           spin_lock(&(t->if_lock));
  42 -#define   if_unlock(t)           spin_unlock(&(t->if_lock));
  43 +#define   if_lock(t)           mutex_lock(&(t->if_lock));
  44 +#define   if_unlock(t)           mutex_unlock(&(t->if_lock));
  45
  46  /* Used to help with determining the pkts on receive */
  47  #define PKTGEN_MAGIC 0xbe9be955
  48 @@ -418,7 +418,7 @@ struct pktgen_net {
  49  };
  50
  51  struct pktgen_thread {
  52 -       spinlock_t if_lock;             /* for list of devices */
  53 +       struct mutex if_lock;           /* for list of devices */
  54         struct list_head if_list;       /* All device here */
  55         struct list_head th_list;
  56         struct task_struct *tsk;
  57 @@ -1952,11 +1952,13 @@ static void pktgen_change_name(const str
  58  {
  59         struct pktgen_thread *t;
  60
  61 +       mutex_lock(&pktgen_thread_lock);
  62 +
  63         list_for_each_entry(t, &pn->pktgen_threads, th_list) {
  64                 struct pktgen_dev *pkt_dev;
  65
  66 -               rcu_read_lock();
  67 -               list_for_each_entry_rcu(pkt_dev, &t->if_list, list) {
  68 +               if_lock(t);
  69 +               list_for_each_entry(pkt_dev, &t->if_list, list) {
  70                         if (pkt_dev->odev != dev)
  71                                 continue;
  72
  73 @@ -1971,8 +1973,9 @@ static void pktgen_change_name(const str
  74                                        dev->name);
  75                         break;
  76                 }
  77 -               rcu_read_unlock();
  78 +               if_unlock(t);
  79         }
  80 +       mutex_unlock(&pktgen_thread_lock);
  81  }
  82
  83  static int pktgen_device_event(struct notifier_block *unused,
  84 @@ -3656,7 +3659,7 @@ static int __net_init pktgen_create_thre
  85                 return -ENOMEM;
  86         }
  87
  88 -       spin_lock_init(&t->if_lock);
  89 +       mutex_init(&t->if_lock);
  90         t->cpu = cpu;
  91
  92         INIT_LIST_HEAD(&t->if_list);