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fix nordic critical section #5595

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merged 2 commits into from Jan 4, 2018
Merged

fix nordic critical section #5595

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b084812
current critical section implementation makes possible that interrupt
nvlsianpu Nov 28, 2017
ae41c7d
Implementation of critical section primitives
nvlsianpu Dec 22, 2017
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99 changes: 72 additions & 27 deletions targets/TARGET_NORDIC/TARGET_NRF5/nordic_critical.c
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Expand Up @@ -15,43 +15,88 @@
* limitations under the License.
*/

#include <stdint.h> // uint32_t, UINT32_MAX
#include <assert.h> // uint32_t, UINT32_MAX
#include "cmsis.h"
#include "nrf_soc.h"
#include "nrf_sdm.h"
#include "nrf_nvic.h"
#include <stdint.h>
#include "app_util_platform.h"

static uint8_t _sd_state = 0;
static volatile uint32_t _entry_count = 0;
#if defined(SOFTDEVICE_PRESENT)
static volatile uint32_t nordic_cr_nested = 0;

static void nordic_nvic_critical_region_enter(void);
static void nordic_nvic_critical_region_exit(void);
#endif

void core_util_critical_section_enter()
{
// if a critical section has already been entered, just update the counter
if (_entry_count) {
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@nvlsianpu nvlsianpu Dec 21, 2017 •
edited

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The one of possibles scenerio for 'previous code 'is:
In routine A _enter_count check could had been positive, then execution of routine can been interrupted by routine B which would call core_util_critical_section_exit. In result after routine A executed core_util_critical_section_enter the critical section is not enabled - and the _entry_count value is equal to 1.

So _entry_count check-modify must be a atomic operation in order to mitigate this and similar scenarios.
This Is exactly how app_util_critical_region_ente call work.

@pan- , @0xc0170
This is answer to:

@nvlsianpu Could you explain what was the root cause ?

++_entry_count;
return;
}

// in this path, a critical section has never been entered
// routine of SD V11 work even if the softdevice is not active
sd_nvic_critical_region_enter(&_sd_state);
#ifdef NRF52
ASSERT(APP_LEVEL_PRIVILEGED == privilege_level_get())
#endif

assert(_entry_count == 0); // entry count should always be equal to 0 at this point
++_entry_count;
#if defined(SOFTDEVICE_PRESENT)
/* return value can be safely ignored */
nordic_nvic_critical_region_enter();
#else
app_util_disable_irq();
#endif
}

void core_util_critical_section_exit()
{
assert(_entry_count > 0);
--_entry_count;
#ifdef NRF52
ASSERT(APP_LEVEL_PRIVILEGED == privilege_level_get())
#endif

#if defined(SOFTDEVICE_PRESENT)
/* return value can be safely ignored */
nordic_nvic_critical_region_exit();
#else
app_util_enable_irq();
#endif
}

#if defined(SOFTDEVICE_PRESENT)
/**@brief Enters critical region.
*
* @post Application interrupts will be disabled.
* @sa nordic_nvic_critical_region_exit
*/
static inline void nordic_nvic_critical_region_enter(void)
{
int was_masked = __sd_nvic_irq_disable();

// If their is other segments which have entered the critical section, just leave
if (_entry_count) {
return;
if (nordic_cr_nested == 0) {
nrf_nvic_state.__irq_masks[0] = ( NVIC->ICER[0] & __NRF_NVIC_APP_IRQS_0 );
NVIC->ICER[0] = __NRF_NVIC_APP_IRQS_0;
#ifdef NRF52
nrf_nvic_state.__irq_masks[1] = ( NVIC->ICER[1] & __NRF_NVIC_APP_IRQS_1 );
NVIC->ICER[1] = __NRF_NVIC_APP_IRQS_1;
#endif
}

// This is the last segment of the critical section, state should be restored as before entering
// the critical section
sd_nvic_critical_region_exit(_sd_state);
nordic_cr_nested++;

if (!was_masked) {
__sd_nvic_irq_enable();
}
}

/**@brief Exit critical region.
*
* @pre Application has entered a critical region using ::nordic_nvic_critical_region_enter.
* @post If not in a nested critical region, the application interrupts will restored to the state before ::nordic_nvic_critical_region_enter was called.
*/
static inline void nordic_nvic_critical_region_exit(void)
{
nordic_cr_nested--;

if (nordic_cr_nested == 0) {
int was_masked = __sd_nvic_irq_disable();
NVIC->ISER[0] = nrf_nvic_state.__irq_masks[0];
#ifdef NRF52
NVIC->ISER[1] = nrf_nvic_state.__irq_masks[1];
#endif
if (!was_masked) {
__sd_nvic_irq_enable();
}
}
}
#endif