Commit 3d068261 authored by Dominik Brodowski's avatar Dominik Brodowski

pcmcia: add locking documentation

Tested-by: default avatarWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 00ce99ff
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
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 are on their own to provide proper locking.
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;
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