releases/2.6.24.1/pci-fix-fakephp-deadlock.patch

   1 From stable-bounces@linux.kernel.org Mon Feb  4 06:11:08 2008
   2 From: Ian Abbott <abbotti@mev.co.uk>
   3 Date: Mon, 04 Feb 2008 13:43:13 +0000
   4 Subject: PCI: Fix fakephp deadlock
   5 To: stable@kernel.org
   6 Cc: linux-pci@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org
   7 Message-ID: <47A71671.7080306@mev.co.uk>
   8
   9
  10 From: Ian Abbott <abbotti@mev.co.uk>
  11
  12 This patch works around a problem in the fakephp driver when a process
  13 writing "0" to a "power" sysfs file to fake removal of a PCI device ends
  14 up deadlocking itself in the sysfs code.
  15
  16 The patch was recently accepted into Linus' tree after the 2.6.24 release:
  17 http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=5c796ae7a7ebe56967ed9b9963d7c16d733635ff
  18
  19 Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
  20 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  21
  22 ---
  23  drivers/pci/hotplug/fakephp.c |   39 +++++++++++++++++++++++++++++++++++----
  24  1 file changed, 35 insertions(+), 4 deletions(-)
  25
  26 --- a/drivers/pci/hotplug/fakephp.c
  27 +++ b/drivers/pci/hotplug/fakephp.c
  28 @@ -39,6 +39,7 @@
  29  #include <linux/init.h>
  30  #include <linux/string.h>
  31  #include <linux/slab.h>
  32 +#include <linux/workqueue.h>
  33  #include "../pci.h"
  34
  35  #if !defined(MODULE)
  36 @@ -63,10 +64,16 @@ struct dummy_slot {
  37         struct list_head node;
  38         struct hotplug_slot *slot;
  39         struct pci_dev *dev;
  40 +       struct work_struct remove_work;
  41 +       unsigned long removed;
  42  };
  43
  44  static int debug;
  45  static LIST_HEAD(slot_list);
  46 +static struct workqueue_struct *dummyphp_wq;
  47 +
  48 +static void pci_rescan_worker(struct work_struct *work);
  49 +static DECLARE_WORK(pci_rescan_work, pci_rescan_worker);
  50
  51  static int enable_slot (struct hotplug_slot *slot);
  52  static int disable_slot (struct hotplug_slot *slot);
  53 @@ -109,7 +116,7 @@ static int add_slot(struct pci_dev *dev)
  54         slot->name = &dev->dev.bus_id[0];
  55         dbg("slot->name = %s\n", slot->name);
  56
  57 -       dslot = kmalloc(sizeof(struct dummy_slot), GFP_KERNEL);
  58 +       dslot = kzalloc(sizeof(struct dummy_slot), GFP_KERNEL);
  59         if (!dslot)
  60                 goto error_info;
  61
  62 @@ -164,6 +171,14 @@ static void remove_slot(struct dummy_slo
  63                 err("Problem unregistering a slot %s\n", dslot->slot->name);
  64  }
  65
  66 +/* called from the single-threaded workqueue handler to remove a slot */
  67 +static void remove_slot_worker(struct work_struct *work)
  68 +{
  69 +       struct dummy_slot *dslot =
  70 +               container_of(work, struct dummy_slot, remove_work);
  71 +       remove_slot(dslot);
  72 +}
  73 +
  74  /**
  75   * pci_rescan_slot - Rescan slot
  76   * @temp: Device template. Should be set: bus and devfn.
  77 @@ -267,11 +282,17 @@ static inline void pci_rescan(void) {
  78         pci_rescan_buses(&pci_root_buses);
  79  }
  80
  81 +/* called from the single-threaded workqueue handler to rescan all pci buses */
  82 +static void pci_rescan_worker(struct work_struct *work)
  83 +{
  84 +       pci_rescan();
  85 +}
  86
  87  static int enable_slot(struct hotplug_slot *hotplug_slot)
  88  {
  89         /* mis-use enable_slot for rescanning of the pci bus */
  90 -       pci_rescan();
  91 +       cancel_work_sync(&pci_rescan_work);
  92 +       queue_work(dummyphp_wq, &pci_rescan_work);
  93         return -ENODEV;
  94  }
  95
  96 @@ -306,6 +327,10 @@ static int disable_slot(struct hotplug_s
  97                 err("Can't remove PCI devices with other PCI devices behind it yet.\n");
  98                 return -ENODEV;
  99         }
 100 +       if (test_and_set_bit(0, &dslot->removed)) {
 101 +               dbg("Slot already scheduled for removal\n");
 102 +               return -ENODEV;
 103 +       }
 104         /* search for subfunctions and disable them first */
 105         if (!(dslot->dev->devfn & 7)) {
 106                 for (func = 1; func < 8; func++) {
 107 @@ -328,8 +353,9 @@ static int disable_slot(struct hotplug_s
 108         /* remove the device from the pci core */
 109         pci_remove_bus_device(dslot->dev);
 110
 111 -       /* blow away this sysfs entry and other parts. */
 112 -       remove_slot(dslot);
 113 +       /* queue work item to blow away this sysfs entry and other parts. */
 114 +       INIT_WORK(&dslot->remove_work, remove_slot_worker);
 115 +       queue_work(dummyphp_wq, &dslot->remove_work);
 116
 117         return 0;
 118  }
 119 @@ -340,6 +366,7 @@ static void cleanup_slots (void)
 120         struct list_head *next;
 121         struct dummy_slot *dslot;
 122
 123 +       destroy_workqueue(dummyphp_wq);
 124         list_for_each_safe (tmp, next, &slot_list) {
 125                 dslot = list_entry (tmp, struct dummy_slot, node);
 126                 remove_slot(dslot);
 127 @@ -351,6 +378,10 @@ static int __init dummyphp_init(void)
 128  {
 129         info(DRIVER_DESC "\n");
 130
 131 +       dummyphp_wq = create_singlethread_workqueue(MY_NAME);
 132 +       if (!dummyphp_wq)
 133 +               return -ENOMEM;
 134 +
 135         return pci_scan_buses();
 136  }
 137