how to use sys_heap_alloc() stablely?

[brook]

In my design, many sys_heap_alloc() would be used to push msg(data) to k_fifo.

but, it always return NULL and cause ASSERT..

the following is my code:

#define HEAP_SIZE   4096

static char heap_mem[HEAP_SIZE];

static struct sys_heap heap;

sys_heap_init(&heap, heap_mem, HEAP_SIZE);

In other location:

sys_heap_alloc(&heap, len);

sys_heap_free(&heap, p);

I would call this frequently. sometimes it would works well.

but it return NULL frequently.

how to use the heap_alloc rightly? 

what requirement is need by SIZE?

what requirement is need by len?

alignment?

I have no idea about this.

thanks in advance.

[brook]

when the sys_heap_alloc fail to allocate memory. it sometimes report:

unexpected heap state

I really donot know what happened

[Håkon Alseth]

Hi,

 

The heap will return NULL if you're out of memory for instance. Based on your statement:

I would call this frequently. sometimes it would works well.

but it return NULL frequently.

This could be a possible source of the alloc operation failing due to space issues.

 

how to use the heap_alloc rightly? 

what requirement is need by SIZE?

what requirement is need by len?

The API and usage of it is documented here: https://docs.zephyrproject.org/latest/kernel/memory_management/heap.html

brook said:

unexpected heap state

This output?

https://github.com/nrfconnect/sdk-zephyr/blob/v3.3.99-ncs1-1/lib/os/heap.c#L176

 

That can indicate a double-free scenario. Are you potentially free'ing the same pointer in different contexts?

 

Kind regards,

Håkon