src/patches/suse-2.6.27.39/patches.arch/ia64-page-migration.fix

   1 From: Russ Anderson <rja@sgi.com>
   2 Subject: ia64: cpe_migrate.ko causes deadlock.
   3 References: bnc#464676
   4
   5 schedule_on_each_cpu() deadlocks when called from an event thread.
   6 Change cpe_migrate to use a kthread to avoid the problem.
   7
   8 Signed-off-by: Russ Anderson <rja@sgi.com>
   9 Acked-by: Raymund Will <rw@suse.de>
  10
  11 ---
  12  arch/ia64/kernel/cpe_migrate.c |   72 +++++++++++++++++++++++++++++++----------
  13  1 file changed, 56 insertions(+), 16 deletions(-)
  14
  15 Index: linux/arch/ia64/kernel/cpe_migrate.c
  16 ===================================================================
  17 --- linux.orig/arch/ia64/kernel/cpe_migrate.c   2009-01-09 11:37:47.130269369 -0600
  18 +++ linux/arch/ia64/kernel/cpe_migrate.c        2009-01-09 11:44:43.658280930 -0600
  19 @@ -22,6 +22,7 @@
  20  #include <linux/page-isolation.h>
  21  #include <linux/memcontrol.h>
  22  #include <linux/kobject.h>
  23 +#include <linux/kthread.h>
  24
  25  #include <asm/page.h>
  26  #include <asm/system.h>
  27 @@ -40,12 +41,15 @@ static struct cpe_info cpe[CE_HISTORY_LE
  28  static int cpe_polling_enabled = 1;
  29  static int cpe_head;
  30  static int cpe_tail;
  31 -static int work_scheduled;
  32  static int mstat_cannot_isolate;
  33  static int mstat_failed_to_discard;
  34  static int mstat_already_marked;
  35  static int mstat_already_on_list;
  36
  37 +/* IRQ handler notifies this wait queue on receipt of an IRQ */
  38 +DECLARE_WAIT_QUEUE_HEAD(cpe_activate_IRQ_wq);
  39 +static DECLARE_COMPLETION(kthread_cpe_migrated_exited);
  40 +int cpe_active;
  41  DEFINE_SPINLOCK(cpe_migrate_lock);
  42
  43  static void
  44 @@ -159,12 +163,12 @@ ia64_mca_cpe_move_page(u64 paddr, u32 no
  45  }
  46
  47  /*
  48 - * ia64_mca_cpe_migrate
  49 - *     The worker that does the actual migration.  It pulls a
  50 - *     physical address off the list and calls the migration code.
  51 + * cpe_process_queue
  52 + *     Pulls the physical address off the list and calls the migration code.
  53 + *     Will process all the addresses on the list.
  54   */
  55 -static void
  56 -ia64_mca_cpe_migrate(struct work_struct *unused)
  57 +void
  58 +cpe_process_queue(void)
  59  {
  60         int ret;
  61         u64 paddr;
  62 @@ -192,10 +196,36 @@ ia64_mca_cpe_migrate(struct work_struct
  63                         cpe_tail = 0;
  64
  65         } while (cpe_tail != cpe_head);
  66 -       work_scheduled = 0;
  67 +       return;
  68 +}
  69 +
  70 +inline int
  71 +cpe_list_empty(void)
  72 +{
  73 +       return (cpe_head == cpe_tail) && (!cpe[cpe_head].paddr);
  74 +}
  75 +
  76 +/*
  77 + * kthread_cpe_migrate
  78 + *     kthread_cpe_migrate is created at module load time and lives
  79 + *     until the module is removed.  When not active, it will sleep.
  80 + */
  81 +static int
  82 +kthread_cpe_migrate(void *ignore)
  83 +{
  84 +       while (cpe_active) {
  85 +               /*
  86 +                * wait for work
  87 +                */
  88 +               (void)wait_event_interruptible(cpe_activate_IRQ_wq,
  89 +                                               (!cpe_list_empty() ||
  90 +                                               !cpe_active));
  91 +               cpe_process_queue();            /* process work */
  92 +       }
  93 +       complete(&kthread_cpe_migrated_exited);
  94 +       return 0;
  95  }
  96
  97 -static DECLARE_WORK(cpe_enable_work, ia64_mca_cpe_migrate);
  98  DEFINE_SPINLOCK(cpe_list_lock);
  99
 100  /*
 101 @@ -227,10 +257,7 @@ cpe_setup_migrate(void *rec)
 102         if (ret < 0)
 103                 return -EINVAL;
 104
 105 -       if ((cpe_head != cpe_tail) || (cpe[cpe_head].paddr != 0))
 106 -               /*
 107 -                * List not empty
 108 -                */
 109 +       if (!cpe_list_empty())
 110                 for (i = 0; i < CE_HISTORY_LENGTH; i++) {
 111                         if (PAGE_ALIGN(cpe[i].paddr) == PAGE_ALIGN(paddr)) {
 112                                 mstat_already_on_list++;
 113 @@ -255,10 +282,7 @@ cpe_setup_migrate(void *rec)
 114         }
 115         spin_unlock(&cpe_list_lock);
 116
 117 -       if (!work_scheduled) {
 118 -               work_scheduled = 1;
 119 -               schedule_work(&cpe_enable_work);
 120 -       }
 121 +       wake_up_interruptible(&cpe_activate_IRQ_wq);
 122
 123         return 1;
 124  }
 125 @@ -395,12 +419,23 @@ static int __init
 126  cpe_migrate_external_handler_init(void)
 127  {
 128         int error;
 129 +       struct task_struct *kthread;
 130
 131         error = sysfs_create_file(kernel_kobj, &badram_attr.attr);
 132         if (error)
 133                 return -EINVAL;
 134
 135         /*
 136 +        * set up the kthread
 137 +        */
 138 +       cpe_active = 1;
 139 +       kthread = kthread_run(kthread_cpe_migrate, NULL, "cpe_migrate");
 140 +       if (IS_ERR(kthread)) {
 141 +               complete(&kthread_cpe_migrated_exited);
 142 +               return -EFAULT;
 143 +       }
 144 +
 145 +       /*
 146          * register external ce handler
 147          */
 148         if (ia64_reg_CE_extension(cpe_setup_migrate)) {
 149 @@ -418,6 +453,11 @@ cpe_migrate_external_handler_exit(void)
 150  {
 151         /* unregister external mca handlers */
 152         ia64_unreg_CE_extension();
 153 +
 154 +       /* Stop kthread */
 155 +       cpe_active = 0;                 /* tell kthread_cpe_migrate to exit */
 156 +       wake_up_interruptible(&cpe_activate_IRQ_wq);
 157 +       wait_for_completion(&kthread_cpe_migrated_exited);
 158
 159         sysfs_remove_file(kernel_kobj, &badram_attr.attr);
 160  }
 161