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found some racing condition and fixed them

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- fixed the racing condition
- introduce a minimal systick LOAD restriction
- add some comments
This commit is contained in:
Gabriel Wang 2021-01-11 18:50:02 +00:00
parent 6ec7874669
commit 2e465bc4c2
4 changed files with 176 additions and 49 deletions
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80
lib/perf_counter.h
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@ -155,26 +155,21 @@
/*============================ LOCAL VARIABLES ===============================*/
/*============================ PROTOTYPES ====================================*/
/* Function: initialise cycle counter service
* and don't forget to tell the function whether the systick is already
* used by user applications.
* Don't worry, this cycle counter service won't affect your existing
* systick service.
*/
extern void init_cycle_counter(bool bSysTickIsOccupied);
/* Function : start_time
This function will be called right before starting the timed portion of the benchmark.
Implementation may be capturing a system timer (as implemented in the example code)
or zeroing some system parameters - e.g. setting the cpu clocks cycles to 0.
*/
extern void start_cycle_counter(void);
/* Function : stop_time
This function will be called right after ending the timed portion of the benchmark.
Implementation may be capturing a system timer (as implemented in the example code)
or other system parameters - e.g. reading the current value of cpu cycles counter.
/*! \brief try to set a start pointer for the performance counter
*! \retval false the LOAD register is too small
*! \retval true performance counter starts
*/
extern bool start_cycle_counter(void);
/*! \brief calculate the elapsed cycle count since the last start point
*!
*! \note you can have multiple stop_cycle_counter following one start point
*!
*! \return the elapsed cycle count.
*/
extern int32_t stop_cycle_counter(void);
/* Function : delay specified us with the help from systick
@ -207,4 +202,55 @@ __attribute__((nothrow))
extern int64_t clock(void);
#endif
/*----------------------------------------------------------------------------*
* Please ignore the following APIs unless you have encountered some known *
* special conditions *
*----------------------------------------------------------------------------*/
/*! \brief initialise cycle counter service
*! and don't forget to tell the function whether the systick is already
*! used by user applications.
*! Don't worry, this cycle counter service won't affect your existing
*! systick service.
*!
*! \note Usually the perf_counter can initialise itself with the help of
*! __attribute__((constructor(255))), this works fine in Arm Compiler
*! 5 (armcc), Arm Compiler 6 (armclang), arm gcc and llvm. It doesn't
*! work for IAR. So, when you are using IAR, please call this function
*! manually to initialise the perf_counter service.
*!
*! \note Perf_counter library assumes that:
*! a. Your project has already using SysTick
*! b. It assumes that you have already implemented the SysTick_Handler
*! c. It assumes that you have enabled the exception handling for
*! SysTick.
*! If these are not the case, please:
*! a. Add an empty SysTick_Handler to your project if you don't have
*! one
*! b. Make sure you have the SysTick Exception handling enabled
*! c. And call function init_cycle_counter(false) if you doesn't
*! use SysTick in your project at all.
*!
*! \param bSysTickIsOccupied A boolean value which indicates whether SysTick
*! is already used by user application.
*/
extern void init_cycle_counter(bool bSysTickIsOccupied);
/*! \note if you are using a compiler rather than armcc or armclang, e.g. iar,
*! arm gcc etc, the systick_wrapper_ual.o doesn't work with the linker
*! of your target toolchain as it use the $Super$$ which is only supported
*! by armlink. For this condition, you have to manually put this function
*! into your existing SysTick_Handler to make the perf_counter library
*! work.
*!
*! \note if you are using Arm Compiler 5 (armcc) or Arm Compiler 6 (armclang)
*! you do NOT have to insert this function into your SysTick_Handler,
*! the systick_wrapper_ual.s will do the work for you.
*/
extern void user_code_insert_to_systick_handler(void);
#endif

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lib/perf_counter.lib
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65
perf_counter.c
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@ -22,6 +22,10 @@
#include "cmsis_compiler.h"
#include "perf_counter.h"
#ifndef PERF_CNT_COMPENSATION_THRESHOLD
# define PERF_CNT_COMPENSATION_THRESHOLD 16
#endif
/*============================ MACROS ========================================*/
/* IO definitions (access restrictions to peripheral registers) */
/**
@ -192,6 +196,14 @@ void user_code_insert_to_systick_handler(void)
s_lSystemClockCounts += wLoad;
}
/*! \brief initialise cycle counter service
*! and don't forget to tell the function whether the systick is already
*! used by user applications.
*! Don't worry, this cycle counter service won't affect your existing
*! systick service.
*! \param bSysTickIsOccupied A boolean value which indicates whether SysTick
*! is already used by user application.
*/
void init_cycle_counter(bool bSysTickIsOccupied)
{
if (!bSysTickIsOccupied) {
@ -205,16 +217,20 @@ void init_cycle_counter(bool bSysTickIsOccupied)
__ensure_systick_wrapper();
}
/* Function : start_time
This function will be called right before starting the timed portion of the benchmark.
Implementation may be capturing a system timer (as implemented in the example code)
or zeroing some system parameters - e.g. setting the cpu clocks cycles to 0.
/*! \brief try to start the performance counter
*! \retval false the LOAD register is too small
*! \retval true performance counter starts
*/
void start_cycle_counter(void)
bool start_cycle_counter(void)
{
if (SysTick->LOAD < PERF_CNT_COMPENSATION_THRESHOLD) {
return false;
}
safe_atom_code(){
s_nCycleCounts = (int32_t)SysTick->VAL - (int32_t)SysTick->LOAD;
}
return true;
}
/*! \note this function should only be called when irq is disabled
@ -225,22 +241,41 @@ static __attribute__((always_inline)) int32_t check_systick(void)
{
int32_t nTemp = (int32_t)SysTick->LOAD - (int32_t)SysTick->VAL;
/*! \note here is a corner case: SysTick->VAL is zero and SysTick Pending bit is set.
*! we should check this corner condition with (nTemp != SysTick->LOAD)
/*! \note Since we cannot stop counting temporarily, there are several
*! conditions which we should take into consideration:
*! Condition one: when assign nTemp with the register value (LOAD-VAL),
*! the underflow didn't happen and when we check the PENDSTSET bit,
*! the underflow happens, for this condition, we should not
*! do any compensation. When this happens, the (LOAD-nTemp) is
*! smaller than PERF_CNT_COMPENSATION_THRESHOLD (a big value) as
*! long as LOAD is bigger than (or equals to) the
*! PERF_CNT_COMPENSATION_THRESHOLD;
*! Condition two: when assign nTemp with the register value (LOAD-VAL),
*! the VAL is zero and underflow happened and the PENDSTSET bit
*! is set, for this condition, we should not do any compensation.
*! When this happens, the (LOAD-nTemp) is equals to zero.
*! Condition Three: when initialising nTemp with the register value
*! VAL, the underflow has already happened, hence the PENDSTSET
*! is set, for this condition, we should compensate the return
*! value. When this happens, the (LOAD-nTemp) is bigger than (or
*! equals to) PERF_CNT_COMPENSATION_THRESHOLD.
*! The following code implements an equivalent logic.
*/
if ( (SCB->ICSR & SCB_ICSR_PENDSTSET_Msk)
&& (nTemp != SysTick->LOAD)) {
nTemp += SysTick->LOAD;
if (SCB->ICSR & SCB_ICSR_PENDSTSET_Msk){
if (((int32_t)SysTick->LOAD - nTemp) >= PERF_CNT_COMPENSATION_THRESHOLD) {
nTemp += SysTick->LOAD;
}
}
return nTemp;
}
/* Function : stop_time
This function will be called right after ending the timed portion of the benchmark.
Implementation may be capturing a system timer (as implemented in the example code)
or other system parameters - e.g. reading the current value of cpu cycles counter.
*/
/*! \brief calculate the elapsed cycle count since the last start point
*!
*! \note you can have multiple stop_cycle_counter following one start point
*!
*! \return the elapsed cycle count.
*/
int32_t stop_cycle_counter(void)
{
int32_t nTemp = 0;

80
perf_counter.h
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@ -155,26 +155,21 @@
/*============================ LOCAL VARIABLES ===============================*/
/*============================ PROTOTYPES ====================================*/
/* Function: initialise cycle counter service
* and don't forget to tell the function whether the systick is already
* used by user applications.
* Don't worry, this cycle counter service won't affect your existing
* systick service.
*/
extern void init_cycle_counter(bool bSysTickIsOccupied);
/* Function : start_time
This function will be called right before starting the timed portion of the benchmark.
Implementation may be capturing a system timer (as implemented in the example code)
or zeroing some system parameters - e.g. setting the cpu clocks cycles to 0.
*/
extern void start_cycle_counter(void);
/* Function : stop_time
This function will be called right after ending the timed portion of the benchmark.
Implementation may be capturing a system timer (as implemented in the example code)
or other system parameters - e.g. reading the current value of cpu cycles counter.
/*! \brief try to set a start pointer for the performance counter
*! \retval false the LOAD register is too small
*! \retval true performance counter starts
*/
extern bool start_cycle_counter(void);
/*! \brief calculate the elapsed cycle count since the last start point
*!
*! \note you can have multiple stop_cycle_counter following one start point
*!
*! \return the elapsed cycle count.
*/
extern int32_t stop_cycle_counter(void);
/* Function : delay specified us with the help from systick
@ -207,4 +202,55 @@ __attribute__((nothrow))
extern int64_t clock(void);
#endif
/*----------------------------------------------------------------------------*
* Please ignore the following APIs unless you have encountered some known *
* special conditions *
*----------------------------------------------------------------------------*/
/*! \brief initialise cycle counter service
*! and don't forget to tell the function whether the systick is already
*! used by user applications.
*! Don't worry, this cycle counter service won't affect your existing
*! systick service.
*!
*! \note Usually the perf_counter can initialise itself with the help of
*! __attribute__((constructor(255))), this works fine in Arm Compiler
*! 5 (armcc), Arm Compiler 6 (armclang), arm gcc and llvm. It doesn't
*! work for IAR. So, when you are using IAR, please call this function
*! manually to initialise the perf_counter service.
*!
*! \note Perf_counter library assumes that:
*! a. Your project has already using SysTick
*! b. It assumes that you have already implemented the SysTick_Handler
*! c. It assumes that you have enabled the exception handling for
*! SysTick.
*! If these are not the case, please:
*! a. Add an empty SysTick_Handler to your project if you don't have
*! one
*! b. Make sure you have the SysTick Exception handling enabled
*! c. And call function init_cycle_counter(false) if you doesn't
*! use SysTick in your project at all.
*!
*! \param bSysTickIsOccupied A boolean value which indicates whether SysTick
*! is already used by user application.
*/
extern void init_cycle_counter(bool bSysTickIsOccupied);
/*! \note if you are using a compiler rather than armcc or armclang, e.g. iar,
*! arm gcc etc, the systick_wrapper_ual.o doesn't work with the linker
*! of your target toolchain as it use the $Super$$ which is only supported
*! by armlink. For this condition, you have to manually put this function
*! into your existing SysTick_Handler to make the perf_counter library
*! work.
*!
*! \note if you are using Arm Compiler 5 (armcc) or Arm Compiler 6 (armclang)
*! you do NOT have to insert this function into your SysTick_Handler,
*! the systick_wrapper_ual.s will do the work for you.
*/
extern void user_code_insert_to_systick_handler(void);
#endif