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authorDominik Brodowski <linux@dominikbrodowski.net>2010-01-16 09:17:10 +0100
committerDominik Brodowski <linux@dominikbrodowski.net>2010-02-17 17:48:21 +0100
commit3d068261854b00c930df4516cd617900935e7706 (patch)
treef2f4a188f74a4b128cca6c1268be9f8b4ae31bcd
parent00ce99ff506a17882747a7d6874e3f5206a99043 (diff)
downloadlinux-linaro-stable-3d068261854b00c930df4516cd617900935e7706.tar.gz
pcmcia: add locking documentation
Tested-by: Wolfram Sang <w.sang@pengutronix.de> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
-rw-r--r--Documentation/pcmcia/locking.txt92
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diff --git a/Documentation/pcmcia/locking.txt b/Documentation/pcmcia/locking.txt
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+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;