releases/6.6.26/driver-core-introduce-device_link_wait_removal.patch

   1 From 0462c56c290a99a7f03e817ae5b843116dfb575c Mon Sep 17 00:00:00 2001
   2 From: Herve Codina <herve.codina@bootlin.com>
   3 Date: Mon, 25 Mar 2024 16:21:25 +0100
   4 Subject: driver core: Introduce device_link_wait_removal()
   5
   6 From: Herve Codina <herve.codina@bootlin.com>
   7
   8 commit 0462c56c290a99a7f03e817ae5b843116dfb575c upstream.
   9
  10 The commit 80dd33cf72d1 ("drivers: base: Fix device link removal")
  11 introduces a workqueue to release the consumer and supplier devices used
  12 in the devlink.
  13 In the job queued, devices are release and in turn, when all the
  14 references to these devices are dropped, the release function of the
  15 device itself is called.
  16
  17 Nothing is present to provide some synchronisation with this workqueue
  18 in order to ensure that all ongoing releasing operations are done and
  19 so, some other operations can be started safely.
  20
  21 For instance, in the following sequence:
  22   1) of_platform_depopulate()
  23   2) of_overlay_remove()
  24
  25 During the step 1, devices are released and related devlinks are removed
  26 (jobs pushed in the workqueue).
  27 During the step 2, OF nodes are destroyed but, without any
  28 synchronisation with devlink removal jobs, of_overlay_remove() can raise
  29 warnings related to missing of_node_put():
  30   ERROR: memory leak, expected refcount 1 instead of 2
  31
  32 Indeed, the missing of_node_put() call is going to be done, too late,
  33 from the workqueue job execution.
  34
  35 Introduce device_link_wait_removal() to offer a way to synchronize
  36 operations waiting for the end of devlink removals (i.e. end of
  37 workqueue jobs).
  38 Also, as a flushing operation is done on the workqueue, the workqueue
  39 used is moved from a system-wide workqueue to a local one.
  40
  41 Cc: stable@vger.kernel.org
  42 Signed-off-by: Herve Codina <herve.codina@bootlin.com>
  43 Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
  44 Reviewed-by: Nuno Sa <nuno.sa@analog.com>
  45 Reviewed-by: Saravana Kannan <saravanak@google.com>
  46 Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  47 Link: https://lore.kernel.org/r/20240325152140.198219-2-herve.codina@bootlin.com
  48 Signed-off-by: Rob Herring <robh@kernel.org>
  49 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  50 ---
  51  drivers/base/core.c    |   26 +++++++++++++++++++++++---
  52  include/linux/device.h |    1 +
  53  2 files changed, 24 insertions(+), 3 deletions(-)
  54
  55 --- a/drivers/base/core.c
  56 +++ b/drivers/base/core.c
  57 @@ -44,6 +44,7 @@ static bool fw_devlink_is_permissive(voi
  58  static void __fw_devlink_link_to_consumers(struct device *dev);
  59  static bool fw_devlink_drv_reg_done;
  60  static bool fw_devlink_best_effort;
  61 +static struct workqueue_struct *device_link_wq;
  62
  63  /**
  64   * __fwnode_link_add - Create a link between two fwnode_handles.
  65 @@ -531,12 +532,26 @@ static void devlink_dev_release(struct d
  66         /*
  67          * It may take a while to complete this work because of the SRCU
  68          * synchronization in device_link_release_fn() and if the consumer or
  69 -        * supplier devices get deleted when it runs, so put it into the "long"
  70 -        * workqueue.
  71 +        * supplier devices get deleted when it runs, so put it into the
  72 +        * dedicated workqueue.
  73          */
  74 -       queue_work(system_long_wq, &link->rm_work);
  75 +       queue_work(device_link_wq, &link->rm_work);
  76  }
  77
  78 +/**
  79 + * device_link_wait_removal - Wait for ongoing devlink removal jobs to terminate
  80 + */
  81 +void device_link_wait_removal(void)
  82 +{
  83 +       /*
  84 +        * devlink removal jobs are queued in the dedicated work queue.
  85 +        * To be sure that all removal jobs are terminated, ensure that any
  86 +        * scheduled work has run to completion.
  87 +        */
  88 +       flush_workqueue(device_link_wq);
  89 +}
  90 +EXPORT_SYMBOL_GPL(device_link_wait_removal);
  91 +
  92  static struct class devlink_class = {
  93         .name = "devlink",
  94         .dev_groups = devlink_groups,
  95 @@ -4090,9 +4105,14 @@ int __init devices_init(void)
  96         sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj);
  97         if (!sysfs_dev_char_kobj)
  98                 goto char_kobj_err;
  99 +       device_link_wq = alloc_workqueue("device_link_wq", 0, 0);
 100 +       if (!device_link_wq)
 101 +               goto wq_err;
 102
 103         return 0;
 104
 105 + wq_err:
 106 +       kobject_put(sysfs_dev_char_kobj);
 107   char_kobj_err:
 108         kobject_put(sysfs_dev_block_kobj);
 109   block_kobj_err:
 110 --- a/include/linux/device.h
 111 +++ b/include/linux/device.h
 112 @@ -1250,6 +1250,7 @@ void device_link_del(struct device_link
 113  void device_link_remove(void *consumer, struct device *supplier);
 114  void device_links_supplier_sync_state_pause(void);
 115  void device_links_supplier_sync_state_resume(void);
 116 +void device_link_wait_removal(void);
 117
 118  /* Create alias, so I can be autoloaded. */
 119  #define MODULE_ALIAS_CHARDEV(major,minor) \