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Merge pull request #5596 from kjbracey-arm/strong_cas 

Make LDREX/STREX CAS functions strong
pull/5586/merge
Martin Kojtal 2017-11-30 18:04:14 +00:00 committed by GitHub
parent 244d8a9c9d 59508d46a6
commit b076565ac0
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 47 additions and 28 deletions
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51
platform/mbed_critical.c
View File

@ -110,39 +110,42 @@ MBED_WEAK void core_util_critical_section_exit(void)
bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue) bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue)
{ {
uint8_t currentValue = __LDREXB((volatile uint8_t*)ptr); do {
if (currentValue != *expectedCurrentValue) { uint8_t currentValue = __LDREXB((volatile uint8_t*)ptr);
*expectedCurrentValue = currentValue; if (currentValue != *expectedCurrentValue) {
__CLREX(); *expectedCurrentValue = currentValue;
return false; __CLREX();
} return false;
}
return !__STREXB(desiredValue, (volatile uint8_t*)ptr); } while (__STREXB(desiredValue, (volatile uint8_t*)ptr));
return true;
} }
bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue) bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue)
{ {
uint16_t currentValue = __LDREXH((volatile uint16_t*)ptr); do {
if (currentValue != *expectedCurrentValue) { uint16_t currentValue = __LDREXH((volatile uint16_t*)ptr);
*expectedCurrentValue = currentValue; if (currentValue != *expectedCurrentValue) {
__CLREX(); *expectedCurrentValue = currentValue;
return false; __CLREX();
} return false;
}
return !__STREXH(desiredValue, (volatile uint16_t*)ptr); } while (__STREXH(desiredValue, (volatile uint16_t*)ptr));
return true;
} }
bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue) bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue)
{ {
uint32_t currentValue = __LDREXW((volatile uint32_t*)ptr); do {
if (currentValue != *expectedCurrentValue) { uint32_t currentValue = __LDREXW((volatile uint32_t*)ptr);
*expectedCurrentValue = currentValue; if (currentValue != *expectedCurrentValue) {
__CLREX(); *expectedCurrentValue = currentValue;
return false; __CLREX();
} return false;
}
return !__STREXW(desiredValue, (volatile uint32_t*)ptr); } while (__STREXW(desiredValue, (volatile uint32_t*)ptr));
return true;
} }
uint8_t core_util_atomic_incr_u8(uint8_t *valuePtr, uint8_t delta) uint8_t core_util_atomic_incr_u8(uint8_t *valuePtr, uint8_t delta)

24
platform/mbed_critical.h
View File

@ -121,7 +121,7 @@ void core_util_critical_section_exit(void);
* } * }
* *
* @note: In the failure case (where the destination isn't set), the value * @note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value. * pointed to by expectedCurrentValue is instead updated with the current value.
* This property helps writing concise code for the following incr: * This property helps writing concise code for the following incr:
* *
* function incr(p : pointer to int, a : int) returns int { * function incr(p : pointer to int, a : int) returns int {
@ -132,6 +132,10 @@ void core_util_critical_section_exit(void);
* } * }
* return value + a * return value + a
* } * }
*
* @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
* always succeeds if the current value is expected, as per the pseudocode
* above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
*/ */
bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue); bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue);
@ -174,7 +178,7 @@ bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_
* } * }
* *
* @note: In the failure case (where the destination isn't set), the value * @note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value. * pointed to by expectedCurrentValue is instead updated with the current value.
* This property helps writing concise code for the following incr: * This property helps writing concise code for the following incr:
* *
* function incr(p : pointer to int, a : int) returns int { * function incr(p : pointer to int, a : int) returns int {
@ -185,6 +189,10 @@ bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_
* } * }
* return value + a * return value + a
* } * }
*
* @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
* always succeeds if the current value is expected, as per the pseudocode
* above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
*/ */
bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue); bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue);
@ -227,7 +235,7 @@ bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uin
* } * }
* *
* @note: In the failure case (where the destination isn't set), the value * @note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value. * pointed to by expectedCurrentValue is instead updated with the current value.
* This property helps writing concise code for the following incr: * This property helps writing concise code for the following incr:
* *
* function incr(p : pointer to int, a : int) returns int { * function incr(p : pointer to int, a : int) returns int {
@ -237,6 +245,10 @@ bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uin
* done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
* } * }
* return value + a * return value + a
*
* @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
* always succeeds if the current value is expected, as per the pseudocode
* above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
* } * }
*/ */
bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue); bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue);
@ -280,7 +292,7 @@ bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uin
* } * }
* *
* @note: In the failure case (where the destination isn't set), the value * @note: In the failure case (where the destination isn't set), the value
* pointed to by expectedCurrentValue is still updated with the current value. * pointed to by expectedCurrentValue is instead updated with the current value.
* This property helps writing concise code for the following incr: * This property helps writing concise code for the following incr:
* *
* function incr(p : pointer to int, a : int) returns int { * function incr(p : pointer to int, a : int) returns int {
@ -291,6 +303,10 @@ bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uin
* } * }
* return value + a * return value + a
* } * }
*
* @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
* always succeeds if the current value is expected, as per the pseudocode
* above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
*/ */
bool core_util_atomic_cas_ptr(void **ptr, void **expectedCurrentValue, void *desiredValue); bool core_util_atomic_cas_ptr(void **ptr, void **expectedCurrentValue, void *desiredValue);