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kernel: mempool: fix race condition in rt_mp_alloc

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When thread wake up from waiting for memory, there is a chance that
there is no memory available in high pressure. So use a loop to check
again. Otherwise, there will be a NULL reference.
This commit is contained in:
Grissiom
2014-08-20 10:16:04 +08:00
parent 0135dd38cf
commit b8bf6bef76
1 changed files with 56 additions and 55 deletions
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43
src/mempool.c
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@@ -323,23 +323,15 @@ void *rt_mp_alloc(rt_mp_t mp, rt_int32_t time)
rt_uint8_t *block_ptr; rt_uint8_t *block_ptr;
register rt_base_t level; register rt_base_t level;
struct rt_thread *thread; struct rt_thread *thread;
rt_uint32_t before_sleep = 0;
/* get current thread */
thread = rt_thread_self();
/* disable interrupt */ /* disable interrupt */
level = rt_hw_interrupt_disable(); level = rt_hw_interrupt_disable();
if (mp->block_free_count) while (mp->block_free_count == 0)
{
/* memory block is available. decrease the free block counter */
mp->block_free_count --;
/* get block from block list */
block_ptr = mp->block_list;
mp->block_list = *(rt_uint8_t **)block_ptr;
/* point to memory pool */
*(rt_uint8_t **)block_ptr = (rt_uint8_t *)mp;
}
else
{ {
/* memory block is unavailable. */ /* memory block is unavailable. */
if (time == 0) if (time == 0)
@@ -347,14 +339,12 @@ void *rt_mp_alloc(rt_mp_t mp, rt_int32_t time)
/* enable interrupt */ /* enable interrupt */
rt_hw_interrupt_enable(level); rt_hw_interrupt_enable(level);
rt_set_errno(-RT_ETIMEOUT);
return RT_NULL; return RT_NULL;
} }
else
{
RT_DEBUG_NOT_IN_INTERRUPT;
/* get current thread */ RT_DEBUG_NOT_IN_INTERRUPT;
thread = rt_thread_self();
thread->error = RT_EOK; thread->error = RT_EOK;
@@ -365,6 +355,9 @@ void *rt_mp_alloc(rt_mp_t mp, rt_int32_t time)
if (time > 0) if (time > 0)
{ {
/* get the start tick of timer */
before_sleep = rt_tick_get();
/* init thread timer and start it */ /* init thread timer and start it */
rt_timer_control(&(thread->thread_timer), rt_timer_control(&(thread->thread_timer),
RT_TIMER_CTRL_SET_TIME, RT_TIMER_CTRL_SET_TIME,
@@ -381,20 +374,28 @@ void *rt_mp_alloc(rt_mp_t mp, rt_int32_t time)
if (thread->error != RT_EOK) if (thread->error != RT_EOK)
return RT_NULL; return RT_NULL;
if (time > 0)
{
time -= rt_tick_get() - before_sleep;
if (time < 0)
time = 0;
}
/* disable interrupt */ /* disable interrupt */
level = rt_hw_interrupt_disable(); level = rt_hw_interrupt_disable();
}
/* decrease free block */ /* memory block is available. decrease the free block counter */
mp->block_free_count--; mp->block_free_count--;
/* get block from block list */ /* get block from block list */
block_ptr = mp->block_list; block_ptr = mp->block_list;
RT_ASSERT(block_ptr != RT_NULL);
/* Setup the next free node. */
mp->block_list = *(rt_uint8_t **)block_ptr; mp->block_list = *(rt_uint8_t **)block_ptr;
/* point to memory pool */ /* point to memory pool */
*(rt_uint8_t **)block_ptr = (rt_uint8_t *)mp; *(rt_uint8_t **)block_ptr = (rt_uint8_t *)mp;
}
}
/* enable interrupt */ /* enable interrupt */
rt_hw_interrupt_enable(level); rt_hw_interrupt_enable(level);