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Introduce ATOMIC_START and ATOMIC_END. 

As a sample application, use it in queue_empty().

There's also ATOMIC_BLOCK() coming with avr-libc, but this requires
a C99 compiler while Arduino IDE insists on running avr-gcc in C89 mode.
This commit is contained in:
Markus Hitter 2013-07-21 22:43:24 +02:00
parent 569adeecd1
commit 69da7c5b15
2 changed files with 13 additions and 7 deletions
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11
dda_queue.c
View File

@ -47,14 +47,11 @@ uint8_t queue_full() {
/// check if the queue is completely empty
uint8_t queue_empty() {
uint8_t save_reg = SREG;
cli();
CLI_SEI_BUG_MEMORY_BARRIER();
uint8_t result = ((mb_tail == mb_head) && (movebuffer[mb_tail].live == 0))?255:0;
uint8_t result;
MEMORY_BARRIER();
SREG = save_reg;
ATOMIC_START
result = ((mb_tail == mb_head) && (movebuffer[mb_tail].live == 0))?255:0;
ATOMIC_END
return result;
}

9
memory_barrier.h
View File

@ -28,4 +28,13 @@
#define CLI_SEI_BUG_MEMORY_BARRIER()
#endif
#define ATOMIC_START { \
uint8_t save_reg = SREG; \
cli(); \
CLI_SEI_BUG_MEMORY_BARRIER();
#define ATOMIC_END MEMORY_BARRIER(); \
SREG = save_reg; \
}
#endif