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ABB semaphore protection overhaul The ABB semaphone protection logic that came with TCS211 from TI was broken in several ways: * Some semaphore-protected functions were called from Application_Initialize() context. NU_Obtain_Semaphore() called with NU_SUSPEND fails with NU_INVALID_SUSPEND in this context, but the return value wasn't checked, and NU_Release_Semaphore() would be called unconditionally at the end. The latter call would increment the semaphore count past 1, making the semaphore no longer binary and thus no longer effective for resource protection. The fix is to check the return value from NU_Obtain_Semaphore() and skip the NU_Release_Semaphore() call if the semaphore wasn't properly obtained. * Some SPI hardware manipulation was being done before entering the semaphore- protected critical section. The fix is to reorder the code: first obtain the semaphore, then do everything else. * In the corner case of L1/DSP recovery, l1_abb_power_on() would call some non-semaphore-protected ABB & SPI init functions. The fix is to skip those calls in the case of recovery. * A few additional corner cases existed, all of which are fixed by making ABB semaphore protection 100% consistent for all ABB functions and code paths. There is still one remaining problem of priority inversion: suppose a low- priority task calls an ABB function, and some medium-priority task just happens to preempt right in the middle of that semaphore-protected ABB operation. Then the high-priority SPI task is locked out for a non-deterministic time until that medium-priority task finishes its work and goes back to sleep. This priority inversion problem remains outstanding for now.
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 26 Apr 2021 20:55:25 +0000
parents fa8dc04885d8
children
line wrap: on
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/*  
+-----------------------------------------------------------------------------
|  Project :  GSM-F&D (8411)
|  Modul   :  gdd_sys.h
+-----------------------------------------------------------------------------
|  Copyright 2005 Texas Instruments Berlin, AG
|                 All rights reserved.
|
|                 This file is confidential and a trade secret of Texas
|                 Instruments Berlin, AG
|                 The receipt of or possession of this file does not convey
|                 any rights to reproduce or disclose its contents or to
|                 manufacture, use, or sell anything it may describe, in
|                 whole, or in part, without the specific written consent of
|                 Texas Instruments Berlin, AG.
+-----------------------------------------------------------------------------
|  Purpose :  API for limited system functionality offered to application
|             domain libraries.
+-----------------------------------------------------------------------------
*/

#ifndef GDD_SYS_H 
#define GDD_SYS_H

/*==== DEFINITIONS ==========================================================*/

typedef int T_GDD_SEM;


/*==== DYNAMIC MEMORY FUNCTIONS =============================================*/


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_mem_malloc
+------------------------------------------------------------------------------
| Description : Allocate memory.
|
| Parameters  : size           - Size of memory required.
|
| Return      : Pointer to first byte of allocated memory.
|               0 if allocation failed.
+------------------------------------------------------------------------------
*/
void * gdd_sys_mem_malloc(int size);


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_mem_free
+------------------------------------------------------------------------------
| Description : Release memory which was previously allocated.
|
| Parameters  : p              - Pointer to memory to be deallocated
+------------------------------------------------------------------------------
*/
void gdd_sys_mem_free(void * p);


/*==== SEMAPHORE FUNCTIONS ==================================================*/


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_sem_open
+------------------------------------------------------------------------------
| Description : Opens a (counting) semaphore specified by its name. If the
|               semaphore does not exist, it will be created with the initial
|               count given. If the semaphore already exists the parameter count
|               will be ignored.
|
| Parameters  : name              - Some name to identify the semaphore
|               count             - initial count (e.g. 1 for a binary sem.)
|
| Return      : Returns handle to created semaphore, or -1 if an error occured.
+------------------------------------------------------------------------------
*/
T_GDD_SEM gdd_sys_sem_open(char * name, unsigned short count);


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_sem_close
+------------------------------------------------------------------------------
| Description : Closes a semaphore
|
| Parameters  : sem               - handle of semaphore
|
| Return      : 0 = succees
|               1 = error
+------------------------------------------------------------------------------
*/
int gdd_sys_sem_close(T_GDD_SEM sem);


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_sem_down
+------------------------------------------------------------------------------
| Description : This functions obtains the specified semaphore, i.e.
|               the counter is decremented, if it is greater than zero.
|               If the counter is equal to zero, than the calling task is
|               suspended until the counter is incremented by another task.
|               If the caller is a non-task thread the function returns
|               immediately regardless if the request can be satisfied or not.
|               In this case, -1 is returned if the counter was already zero. 
|
| Parameters  : sem               - handle of semaphore
|
| Return      : 0 = succees
|               1 = error
+------------------------------------------------------------------------------
*/
int gdd_sys_sem_down(T_GDD_SEM sem);


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_sem_down
+------------------------------------------------------------------------------
| Description : Releases a semaphore, i.e. counter is incremented.
|
| Parameters  : sem               - handle of semaphore
|
| Return      : 0 = succees
|               1 = error
+------------------------------------------------------------------------------
*/
int gdd_sys_sem_up(T_GDD_SEM sem);


/*
+------------------------------------------------------------------------------
| Function    : gdd_sys_sem_status
+------------------------------------------------------------------------------
| Description : Query (obtain) the counter of a semaphore.
|
| Parameters  : sem               - handle of semaphore
|               count             - output variable to pass back the counter
|
| Return      : 0 = succees
|               1 = error
+------------------------------------------------------------------------------
*/
int gdd_sys_sem_status(T_GDD_SEM sem, /*out*/ unsigned short * count);


#endif /* GDD_SYS_H */