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Merge pull request #1843 from c1728p9/atomic_access 

Add functions for atomic access
pull/1856/head
Martin Kojtal 2016-06-06 11:29:32 +01:00
parent d1ec4beabe f3b1d45963
commit 47e2e09df4
2 changed files with 423 additions and 0 deletions
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209
hal/api/critical.h
View File

@ -18,6 +18,8 @@
#ifndef __MBED_UTIL_CRITICAL_H__
#define __MBED_UTIL_CRITICAL_H__
#include <stdbool.h>
#ifdef __cplusplus
extern "C" {
#endif
@ -48,6 +50,213 @@ void core_util_critical_section_enter();
*/
void core_util_critical_section_exit();
/**
* Atomic compare and set. It compares the contents of a memory location to a
* given value and, only if they are the same, modifies the contents of that
* memory location to a given new value. This is done as a single atomic
* operation. The atomicity guarantees that the new value is calculated based on
* up-to-date information; if the value had been updated by another thread in
* the meantime, the write would fail due to a mismatched expectedCurrentValue.
*
* Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
* you to the article on compare-and swap].
*
* @param ptr The target memory location.
* @param[in,out] expectedCurrentValue A pointer to some location holding the
* expected current value of the data being set atomically.
* The computed 'desiredValue' should be a function of this current value.
* @Note: This is an in-out parameter. In the
* failure case of atomic_cas (where the
* destination isn't set), the pointee of expectedCurrentValue is
* updated with the current value.
* @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
*
* @return true if the memory location was atomically
* updated with the desired value (after verifying
* that it contained the expectedCurrentValue),
* false otherwise. In the failure case,
* exepctedCurrentValue is updated with the new
* value of the target memory location.
*
* pseudocode:
* function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
* if *p != *old {
* *old = *p
* return false
* }
* *p = new
* return true
* }
*
* @Note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value.
* This property helps writing concise code for the following incr:
*
* function incr(p : pointer to int, a : int) returns int {
* done = false
* *value = *p // This fetch operation need not be atomic.
* while not done {
* done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
* }
* return value + a
* }
*/
bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue);
/**
* Atomic compare and set. It compares the contents of a memory location to a
* given value and, only if they are the same, modifies the contents of that
* memory location to a given new value. This is done as a single atomic
* operation. The atomicity guarantees that the new value is calculated based on
* up-to-date information; if the value had been updated by another thread in
* the meantime, the write would fail due to a mismatched expectedCurrentValue.
*
* Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
* you to the article on compare-and swap].
*
* @param ptr The target memory location.
* @param[in,out] expectedCurrentValue A pointer to some location holding the
* expected current value of the data being set atomically.
* The computed 'desiredValue' should be a function of this current value.
* @Note: This is an in-out parameter. In the
* failure case of atomic_cas (where the
* destination isn't set), the pointee of expectedCurrentValue is
* updated with the current value.
* @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
*
* @return true if the memory location was atomically
* updated with the desired value (after verifying
* that it contained the expectedCurrentValue),
* false otherwise. In the failure case,
* exepctedCurrentValue is updated with the new
* value of the target memory location.
*
* pseudocode:
* function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
* if *p != *old {
* *old = *p
* return false
* }
* *p = new
* return true
* }
*
* @Note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value.
* This property helps writing concise code for the following incr:
*
* function incr(p : pointer to int, a : int) returns int {
* done = false
* *value = *p // This fetch operation need not be atomic.
* while not done {
* done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
* }
* return value + a
* }
*/
bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue);
/**
* Atomic compare and set. It compares the contents of a memory location to a
* given value and, only if they are the same, modifies the contents of that
* memory location to a given new value. This is done as a single atomic
* operation. The atomicity guarantees that the new value is calculated based on
* up-to-date information; if the value had been updated by another thread in
* the meantime, the write would fail due to a mismatched expectedCurrentValue.
*
* Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
* you to the article on compare-and swap].
*
* @param ptr The target memory location.
* @param[in,out] expectedCurrentValue A pointer to some location holding the
* expected current value of the data being set atomically.
* The computed 'desiredValue' should be a function of this current value.
* @Note: This is an in-out parameter. In the
* failure case of atomic_cas (where the
* destination isn't set), the pointee of expectedCurrentValue is
* updated with the current value.
* @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
*
* @return true if the memory location was atomically
* updated with the desired value (after verifying
* that it contained the expectedCurrentValue),
* false otherwise. In the failure case,
* exepctedCurrentValue is updated with the new
* value of the target memory location.
*
* pseudocode:
* function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
* if *p != *old {
* *old = *p
* return false
* }
* *p = new
* return true
* }
*
* @Note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value.
* This property helps writing concise code for the following incr:
*
* function incr(p : pointer to int, a : int) returns int {
* done = false
* *value = *p // This fetch operation need not be atomic.
* while not done {
* done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
* }
* return value + a
* }
*/
bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue);
/**
* Atomic increment.
* @param valuePtr Target memory location being incremented.
* @param delta The amount being incremented.
* @return The new incremented value.
*/
uint8_t core_util_atomic_incr_u8(uint8_t * valuePtr, uint8_t delta);
/**
* Atomic increment.
* @param valuePtr Target memory location being incremented.
* @param delta The amount being incremented.
* @return The new incremented value.
*/
uint16_t core_util_atomic_incr_u16(uint16_t * valuePtr, uint16_t delta);
/**
* Atomic increment.
* @param valuePtr Target memory location being incremented.
* @param delta The amount being incremented.
* @return The new incremented value.
*/
uint32_t core_util_atomic_incr_u32(uint32_t * valuePtr, uint32_t delta);
/**
* Atomic decrement.
* @param valuePtr Target memory location being decremented.
* @param delta The amount being decremented.
* @return The new decremented value.
*/
uint8_t core_util_atomic_decr_u8(uint8_t * valuePtr, uint8_t delta);
/**
* Atomic decrement.
* @param valuePtr Target memory location being decremented.
* @param delta The amount being decremented.
* @return The new decremented value.
*/
uint16_t core_util_atomic_decr_u16(uint16_t * valuePtr, uint16_t delta);
/**
* Atomic decrement.
* @param valuePtr Target memory location being decremented.
* @param delta The amount being decremented.
* @return The new decremented value.
*/
uint32_t core_util_atomic_decr_u32(uint32_t * valuePtr, uint32_t delta);
#ifdef __cplusplus
} // extern "C"
#endif

214
hal/common/critical.c
View File

@ -24,6 +24,8 @@
// Module include
#include "critical.h"
#define EXCLUSIVE_ACCESS (!defined (__CORTEX_M0) && !defined (__CORTEX_M0PLUS))
static volatile uint32_t interrupt_enable_counter = 0;
static volatile uint32_t critical_primask = 0;
@ -66,3 +68,215 @@ void core_util_critical_section_exit()
}
}
}
#if EXCLUSIVE_ACCESS
bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue)
{
uint8_t currentValue = __LDREXB((volatile uint8_t*)ptr);
if (currentValue != *expectedCurrentValue) {
*expectedCurrentValue = currentValue;
__CLREX();
return false;
}
return !__STREXB(desiredValue, (volatile uint8_t*)ptr);
}
bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue)
{
uint16_t currentValue = __LDREXH((volatile uint16_t*)ptr);
if (currentValue != *expectedCurrentValue) {
*expectedCurrentValue = currentValue;
__CLREX();
return false;
}
return !__STREXH(desiredValue, (volatile uint16_t*)ptr);
}
bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue)
{
uint32_t currentValue = __LDREXW((volatile uint32_t*)ptr);
if (currentValue != *expectedCurrentValue) {
*expectedCurrentValue = currentValue;
__CLREX();
return false;
}
return !__STREXW(desiredValue, (volatile uint32_t*)ptr);
}
uint8_t core_util_atomic_incr_u8(uint8_t * valuePtr, uint8_t delta)
{
uint8_t newValue;
do {
newValue = __LDREXB((volatile uint8_t*)valuePtr) + delta;
} while (__STREXB(newValue, (volatile uint8_t*)valuePtr));
return newValue;
}
uint16_t core_util_atomic_incr_u16(uint16_t * valuePtr, uint16_t delta)
{
uint16_t newValue;
do {
newValue = __LDREXH((volatile uint16_t*)valuePtr) + delta;
} while (__STREXH(newValue, (volatile uint16_t*)valuePtr));
return newValue;
}
uint32_t core_util_atomic_incr_u32(uint32_t * valuePtr, uint32_t delta)
{
uint32_t newValue;
do {
newValue = __LDREXW((volatile uint32_t*)valuePtr) + delta;
} while (__STREXW(newValue, (volatile uint32_t*)valuePtr));
return newValue;
}
uint8_t core_util_atomic_decr_u8(uint8_t * valuePtr, uint8_t delta)
{
uint8_t newValue;
do {
newValue = __LDREXB((volatile uint8_t*)valuePtr) - delta;
} while (__STREXB(newValue, (volatile uint8_t*)valuePtr));
return newValue;
}
uint16_t core_util_atomic_decr_u16(uint16_t * valuePtr, uint16_t delta)
{
uint16_t newValue;
do {
newValue = __LDREXH((volatile uint16_t*)valuePtr) - delta;
} while (__STREXH(newValue, (volatile uint16_t*)valuePtr));
return newValue;
}
uint32_t core_util_atomic_decr_u32(uint32_t * valuePtr, uint32_t delta)
{
uint32_t newValue;
do {
newValue = __LDREXW((volatile uint32_t*)valuePtr) - delta;
} while (__STREXW(newValue, (volatile uint32_t*)valuePtr));
return newValue;
}
#else
bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue)
{
bool success;
uint8_t currentValue;
core_util_critical_section_enter();
currentValue = *ptr;
if (currentValue == *expectedCurrentValue) {
*ptr = desiredValue;
success = true;
} else {
*expectedCurrentValue = currentValue;
success = false;
}
core_util_critical_section_exit();
return success;
}
bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue)
{
bool success;
uint16_t currentValue;
core_util_critical_section_enter();
currentValue = *ptr;
if (currentValue == *expectedCurrentValue) {
*ptr = desiredValue;
success = true;
} else {
*expectedCurrentValue = currentValue;
success = false;
}
core_util_critical_section_exit();
return success;
}
bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue)
{
bool success;
uint32_t currentValue;
core_util_critical_section_enter();
currentValue = *ptr;
if (currentValue == *expectedCurrentValue) {
*ptr = desiredValue;
success = true;
} else {
*expectedCurrentValue = currentValue;
success = false;
}
core_util_critical_section_exit();
return success;
}
uint8_t core_util_atomic_incr_u8(uint8_t * valuePtr, uint8_t delta)
{
uint8_t newValue;
core_util_critical_section_enter();
newValue = *valuePtr + delta;
*valuePtr = newValue;
core_util_critical_section_exit();
return newValue;
}
uint16_t core_util_atomic_incr_u16(uint16_t * valuePtr, uint16_t delta)
{
uint16_t newValue;
core_util_critical_section_enter();
newValue = *valuePtr + delta;
*valuePtr = newValue;
core_util_critical_section_exit();
return newValue;
}
uint32_t core_util_atomic_incr_u32(uint32_t * valuePtr, uint32_t delta)
{
uint32_t newValue;
core_util_critical_section_enter();
newValue = *valuePtr + delta;
*valuePtr = newValue;
core_util_critical_section_exit();
return newValue;
}
uint8_t core_util_atomic_decr_u8(uint8_t * valuePtr, uint8_t delta)
{
uint8_t newValue;
core_util_critical_section_enter();
newValue = *valuePtr - delta;
*valuePtr = newValue;
core_util_critical_section_exit();
return newValue;
}
uint16_t core_util_atomic_decr_u16(uint16_t * valuePtr, uint16_t delta)
{
uint16_t newValue;
core_util_critical_section_enter();
newValue = *valuePtr - delta;
*valuePtr = newValue;
core_util_critical_section_exit();
return newValue;
}
uint32_t core_util_atomic_decr_u32(uint32_t * valuePtr, uint32_t delta)
{
uint32_t newValue;
core_util_critical_section_enter();
newValue = *valuePtr - delta;
*valuePtr = newValue;
core_util_critical_section_exit();
return newValue;
}
#endif