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atomic.h
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atomic.h
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/*
* This file is part of Cleanflight.
*
* Cleanflight is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Cleanflight is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Cleanflight. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
// only set_BASEPRI is implemented in device library. It does always create memory barrier
// missing versions are implemented here
#ifdef UNIT_TEST
static inline void __set_BASEPRI(uint32_t basePri) {(void)basePri;}
static inline void __set_BASEPRI_MAX(uint32_t basePri) {(void)basePri;}
static inline void __set_BASEPRI_nb(uint32_t basePri) {(void)basePri;}
static inline void __set_BASEPRI_MAX_nb(uint32_t basePri) {(void)basePri;}
#else
// set BASEPRI and BASEPRI_MAX register, but do not create memory barrier
__attribute__( ( always_inline ) ) static inline void __set_BASEPRI_nb(uint32_t basePri)
{
__ASM volatile ("\tMSR basepri, %0\n" : : "r" (basePri) );
}
__attribute__( ( always_inline ) ) static inline void __set_BASEPRI_MAX_nb(uint32_t basePri)
{
__ASM volatile ("\tMSR basepri_max, %0\n" : : "r" (basePri) );
}
#endif // UNIT_TEST
// cleanup BASEPRI restore function, with global memory barrier
static inline void __basepriRestoreMem(uint8_t *val)
{
__set_BASEPRI(*val);
}
// set BASEPRI_MAX function, with global memory barrier, returns true
static inline uint8_t __basepriSetMemRetVal(uint8_t prio)
{
__set_BASEPRI_MAX(prio);
return 1;
}
// cleanup BASEPRI restore function, no memory barrier
static inline void __basepriRestore(uint8_t *val)
{
__set_BASEPRI_nb(*val);
}
// set BASEPRI_MAX function, no memory barrier, returns true
static inline uint8_t __basepriSetRetVal(uint8_t prio)
{
__set_BASEPRI_MAX_nb(prio);
return 1;
}
// Run block with elevated BASEPRI (using BASEPRI_MAX), restoring BASEPRI on exit. All exit paths are handled
// Full memory barrier is placed at start and exit of block
#ifdef UNIT_TEST
#define ATOMIC_BLOCK(prio) {}
#define ATOMIC_BLOCK_NB(prio) {}
#else
#define ATOMIC_BLOCK(prio) for ( uint8_t __basepri_save __attribute__((__cleanup__(__basepriRestoreMem))) = __get_BASEPRI(), \
__ToDo = __basepriSetMemRetVal(prio); __ToDo ; __ToDo = 0 )
// Run block with elevated BASEPRI (using BASEPRI_MAX), but do not create any (explicit) memory barrier.
// Be careful when using this, you must use some method to prevent optimizer form breaking things
// - lto is used for Cleanflight compilation, so function call is not memory barrier
// - use ATOMIC_BARRIER or proper volatile to protect used variables
// - gcc 4.8.4 does write all values in registers to memory before 'asm volatile', so this optimization does not help much
// but that can change in future versions
#define ATOMIC_BLOCK_NB(prio) for ( uint8_t __basepri_save __attribute__((__cleanup__(__basepriRestore))) = __get_BASEPRI(), \
__ToDo = __basepriSetRetVal(prio); __ToDo ; __ToDo = 0 ) \
#endif // UNIT_TEST
// ATOMIC_BARRIER
// Create memory barrier
// - at the beginning (all data must be reread from memory)
// - at exit of block (all exit paths) (all data must be written, but may be cached in register for subsequent use)
// ideally this would only protect memory passed as parameter (any type should work), but gcc is currently creating almost full barrier
// this macro can be used only ONCE PER LINE, but multiple uses per block are fine
#if (__GNUC__ > 7)
#warning "Please verify that ATOMIC_BARRIER works as intended"
// increment version number is BARRIER works
// TODO - use flag to disable ATOMIC_BARRIER and use full barrier instead
// you should check that local variable scope with cleanup spans entire block
#endif
#ifndef __UNIQL
# define __UNIQL_CONCAT2(x,y) x ## y
# define __UNIQL_CONCAT(x,y) __UNIQL_CONCAT2(x,y)
# define __UNIQL(x) __UNIQL_CONCAT(x,__LINE__)
#endif
// this macro uses local function for cleanup. CLang block can be substituted
#define ATOMIC_BARRIER(data) \
__extension__ void __UNIQL(__barrierEnd)(typeof(data) **__d) { \
__asm__ volatile ("\t# barier(" #data ") end\n" : : "m" (**__d)); \
} \
typeof(data) __attribute__((__cleanup__(__UNIQL(__barrierEnd)))) *__UNIQL(__barrier) = &data; \
__asm__ volatile ("\t# barier (" #data ") start\n" : "+m" (*__UNIQL(__barrier)))
// define these wrappers for atomic operations, use gcc buildins
#define ATOMIC_OR(ptr, val) __sync_fetch_and_or(ptr, val)
#define ATOMIC_AND(ptr, val) __sync_fetch_and_and(ptr, val)