my problem is how to use malloc or free function in interrupt function,because the function like malloc() or free() is non_reentrant.But i have to do it in interrupt function to save memory. what shall i do? please help me! i use timer0 to free the memory when memeory is no applied,but after three times,the timero is closed auto. the warning is: multi call to a segment free() or malloc(); i describe my algorithm as below: 1)i make the data to link list firstly; 2)in timer0, i will write the node of the link list to CAN bus buffer, after it ,i will free the node.but the timer0 just work 3 times,when it gets the fourth ,the timer0 is closed auto, what shall i do?? regards!! thanks !!
The memory pool accessed via malloc() is a shared resource, with shared internal data structures. Like any shared resource, if you are going to use it from two different contexts -- such as the main code and an ISR -- you're going to need to assure that only one context can have access to the critical section at a time. In short, all your accesses to malloc() will have to be wrapped in calls to disable the interrupt that also calls malloc(). (The other solutions to reentrancy -- writing two routines or declaring the routine reentrant -- do not apply in this case because it's not the code in the function that's the problem so much as the shared memory heap.) Malloc has a relatively long and variable execution time that may make it undesirable in your interrupt handler. Do you really need a linked list for your CAN data to be output, or will a ring buffer do? Unless you actually need the ability of the list to insert into the middle of existing data, the list management is likely to be overhead you don't need.
"Unless you actually need the ability of the list to insert into the middle of existing data" You don't even need malloc to do that! Just have a fixed-size pool of list entries, which are either "free" or "in-use" You can then easily take a "free" entry and "splice" it anywhere into your "in-use" list by simply adjusting the link pointers.