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Critical section - fix for cortex-a #1856

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Merged
merged 1 commit into from
Jun 6, 2016
Merged

Critical section - fix for cortex-a #1856

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26 changes: 18 additions & 8 deletions hal/common/critical.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,24 +27,34 @@
#define EXCLUSIVE_ACCESS (!defined (__CORTEX_M0) && !defined (__CORTEX_M0PLUS))

static volatile uint32_t interrupt_enable_counter = 0;
static volatile uint32_t critical_primask = 0;
static volatile uint32_t critical_interrupts_disabled = 0;

static inline uint32_t get_interrupts_disabled(void)
{
#if defined(__CORTEX_A9)
uint32_t interrupts_disabled = (__get_CPSR() & 0x80) >> 7;
#else
uint32_t interrupts_disabled = __get_PRIMASK();
#endif
return interrupts_disabled;
}

void core_util_critical_section_enter()
{
uint32_t primask = __get_PRIMASK(); /* get the current interrupt enabled state */
uint32_t interrupts_disabled = get_interrupts_disabled();
__disable_irq();

/* Save the interrupt enabled state as it was prior to any nested critical section lock use */
/* Save the interrupt disabled state as it was prior to any nested critical section lock use */
if (!interrupt_enable_counter) {
critical_primask = primask & 0x1;
critical_interrupts_disabled = interrupts_disabled & 0x1;
}

/* If the interrupt_enable_counter overflows or we are in a nested critical section and interrupts
are enabled, then something has gone badly wrong thus assert an error.
*/
MBED_ASSERT(interrupt_enable_counter < UINT32_MAX);
if (interrupt_enable_counter > 0) {
MBED_ASSERT(primask & 0x1);
MBED_ASSERT(interrupts_disabled & 0x1);
}
interrupt_enable_counter++;
}
Expand All @@ -54,16 +64,16 @@ void core_util_critical_section_exit()
/* If critical_section_enter has not previously been called, do nothing */
if (interrupt_enable_counter) {

uint32_t primask = __get_PRIMASK(); /* get the current interrupt enabled state */
uint32_t interrupts_disabled = get_interrupts_disabled(); /* get the current interrupt disabled state */

MBED_ASSERT(primask & 0x1); /* Interrupts must be disabled on invoking an exit from a critical section */
MBED_ASSERT(interrupts_disabled & 0x1); /* Interrupts must be disabled on invoking an exit from a critical section */

interrupt_enable_counter--;

/* Only re-enable interrupts if we are exiting the last of the nested critical sections and
interrupts were enabled on entry to the first critical section.
*/
if (!interrupt_enable_counter && !critical_primask) {
if (!interrupt_enable_counter && !critical_interrupts_disabled) {
__enable_irq();
}
}
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