[Freeipmi-devel] libfreipmi: Locking and Synchronization

[Anand Babu]

Implements mutex based on Sys V Semaphores.

IPMI_IPCKEY 

   PATH: "/var/lock/libfreeipmi/ipckey"
   Uses ftok () and PROJ_ID to generate KEYS.


IPCKEY APIs:

   IPMI_LAN_IPCKEY ()
   IPMI_KCS_IPCKEY ()
   IPMI_SMIC_IPCKEY ()
   IPMI_BT_IPCKEY ()
   Returns 'key'.


Initialization API:

   int ipmi_mutex_init (key_t key);
   Returns 'semid'.


Locking APIs:

   IPMI_MUTEX_LOCK(semid)
   IPMI_MUTEX_UNLOCK(semid)
   IPMI_MUTEX_DOWN (semid)
   IPMI_MUTEX_UP (semid)
   Returns 'void'

   IPMI_MUTEX_LOCK_INTERRUPTIBLE (semid)
   IPMI_MUTEX_LOCK_ASYNC (semid)
   IPMI_MUTEX_DOWN_INTERRUPTIBLE (semid)
   IPMI_MUTEX_DOWN_ASYNC (semid)
   Return '0' on success, otherwise it returns '-1' with errno
   indicating the error. Should restart when errno is 'EAGAIN'.

KCS Driver:

   int ipmi_kcs_get_mutex_semid (void);

   int ipmi_kcs_io_init (u_int16_t sms_io_base, unsigned long
                        sleep_usecs);
   Initialized locking internally.
                        
   int8_t ipmi_kcs_cmd (u_int16_t sms_io_base, u_int8_t lun, u_int8_t
                fn, fiid_obj_t obj_cmd_rq, fiid_template_t
                tmpl_cmd_rq, fiid_obj_t obj_cmd_rs, fiid_template_t
                tmpl_cmd_rs);
   Locking handled internally. Handles BMC transaction - write and
   read.

   int8_t ipmi_kcs_cmd_interruptible (u_int16_t sms_io_base, u_int8_t
             lun, u_int8_t fn, fiid_obj_t obj_cmd_rq, fiid_template_t
             tmpl_cmd_rq, fiid_obj_t obj_cmd_rs, fiid_template_t
             tmpl_cmd_rs);
   Interruptible Locking. Should retry when errno is EAGAIN.
    Handles BMC transaction - write and read.


Notes:
  * Unlocking on exit or crash is handled automatically.
  * You can use "ipcs" and "ipcrm" utilities to view and manipulate
    these mutexes. 
    
-- 
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