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XorShift128: Add some protection to handle the case where this logic could be called from the interrupt level.

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This commit is contained in:
Gregory Nutt 2016-08-20 17:27:41 -06:00
parent 53b2de18eb
commit 757023a909
1 changed files with 52 additions and 1 deletions
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53
libc/misc/lib_xorshift128.c
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@ -42,7 +42,19 @@
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <sched.h>
#include <nuttx/irq.h>
/****************************************************************************
* Private Types
****************************************************************************/
#ifndef CONFIG_CPULOAD_ONESHOT_ENTROPY
# define CONFIG_CPULOAD_ONESHOT_ENTROPY 0
#endif
/****************************************************************************
* Private Types
@ -82,12 +94,30 @@ static struct xorshift128_state_s g_prng;
void xorshift128_seed(uint32_t w, uint32_t x, uint32_t y, uint32_t z)
{
/* With CONFIG_CPULOAD_ONESHOT_ENTROPY > 0, this PRNG could be called from
* the interrupt handling state (currently is not).
*/
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
irqstate_t flags;
flags = enter_critical_section();
#else
sched_lock();
#endif
/* Seed the PRNG */
g_prng.w = w;
g_prng.x = x;
g_prng.y = y;
g_prng.z = z;
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
leave_critical_section(flags);
#else
sched_unlock();
#endif
}
/****************************************************************************
@ -106,8 +136,21 @@ void xorshift128_seed(uint32_t w, uint32_t x, uint32_t y, uint32_t z)
uint32_t xorshift128(void)
{
uint32_t ret;
uint32_t t;
/* With CONFIG_CPULOAD_ONESHOT_ENTROPY > 0, this PRNG will be called from
* the interrupt handling state.
*/
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
irqstate_t flags;
flags = enter_critical_section();
#else
sched_lock();
#endif
t = g_prng.x;
t ^= t << 11;
t ^= t >> 8;
@ -119,5 +162,13 @@ uint32_t xorshift128(void)
g_prng.w ^= g_prng.w >> 19;
g_prng.w ^= t;
return g_prng.w;
ret = g_prng.w;
#if CONFIG_CPULOAD_ONESHOT_ENTROPY > 0
leave_critical_section(flags);
#else
sched_unlock();
#endif
return ret;
}