Locking

This file explains the locking and exclusion scheme used in the PCCARD and PCMCIA subsystems.

A) Overview, Locking Hierarchy:

pcmcia_socket_list_rwsem

• protects only the list of sockets

• skt_mutex

  • serializes card insert / ejection

  • ops_mutex

    • serializes socket operation

B) Exclusion

The following functions and callbacks to struct pcmcia_socket must be called with “skt_mutex” held:

socket_detect_change()
send_event()
socket_reset()
socket_shutdown()
socket_setup()
socket_remove()
socket_insert()
socket_early_resume()
socket_late_resume()
socket_resume()
socket_suspend()

struct pcmcia_callback  *callback

The following functions and callbacks to struct pcmcia_socket must be called with “ops_mutex” held:

socket_reset()
socket_setup()

struct pccard_operations        *ops
struct pccard_resource_ops      *resource_ops;

Note that send_event() and struct pcmcia_callback *callback must not be called with “ops_mutex” held.

C) Protection

1. Global Data:

struct list_head pcmcia_socket_list;

protected by pcmcia_socket_list_rwsem;

2. Per-Socket Data:

The resource_ops and their data are protected by ops_mutex.

The “main” struct pcmcia_socket is protected as follows (read-only fields or single-use fields not mentioned):

• by pcmcia_socket_list_rwsem:

  struct list_head        socket_list;
  

• by thread_lock:

  unsigned int            thread_events;
  

• by skt_mutex:

  u_int                   suspended_state;
  void                    (*tune_bridge);
  struct pcmcia_callback  *callback;
  int                     resume_status;
  

• by ops_mutex:

  socket_state_t          socket;
  u_int                   state;
  u_short                 lock_count;
  pccard_mem_map          cis_mem;
  void __iomem            *cis_virt;
  struct { }              irq;
  io_window_t             io[];
  pccard_mem_map          win[];
  struct list_head        cis_cache;
  size_t                  fake_cis_len;
  u8                      *fake_cis;
  u_int                   irq_mask;
  void                    (*zoom_video);
  int                     (*power_hook);
  u8                      resource...;
  struct list_head        devices_list;
  u8                      device_count;
  struct                  pcmcia_state;
  

3. Per PCMCIA-device Data:

The “main” struct pcmcia_device is protected as follows (read-only fields or single-use fields not mentioned):

• by pcmcia_socket->ops_mutex:

  struct list_head        socket_device_list;
  struct config_t         *function_config;
  u16                     _irq:1;
  u16                     _io:1;
  u16                     _win:4;
  u16                     _locked:1;
  u16                     allow_func_id_match:1;
  u16                     suspended:1;
  u16                     _removed:1;
  

• by the PCMCIA driver:

  io_req_t                io;
  irq_req_t               irq;
  config_req_t            conf;
  window_handle_t         win;