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SubjectRe: [PATCH 4 of 4] Introduce aio system call submission and completion system calls
On Tue, 30 Jan 2007, Zach Brown wrote:

> +void asys_task_exiting(struct task_struct *tsk)
> +{
> + struct asys_result *res, *next;
> +
> + list_for_each_entry_safe(res, next, &tsk->asys_completed, item)
> + kfree(res);
> +
> + /*
> + * XXX this only works if tsk->fibril was allocated by
> + * sys_asys_submit(), not if its embedded in an asys_call. This
> + * implies that we must forbid sys_exit in asys_submit.
> + */
> + if (tsk->fibril) {
> + BUG_ON(!list_empty(&tsk->fibril->run_list));
> + kfree(tsk->fibril);
> + tsk->fibril = NULL;
> + }
> +}

What happens to lingering fibrils? Better keep track of both runnable and
sleepers, and do proper cleanup.



> +asmlinkage long sys_asys_submit(struct asys_input __user *user_inp,
> + unsigned long nr_inp)
> +{
> + struct asys_input inp;
> + struct asys_result *res;
> + struct asys_call *call;
> + struct thread_info *ti;
> + unsigned long i;
> + long err = 0;
> +
> + /* Allocate a fibril for the submitter's thread_info */
> + if (current->fibril == NULL) {
> + current->fibril = kzalloc(sizeof(struct fibril), GFP_KERNEL);
> + if (current->fibril == NULL)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&current->fibril->run_list);
> + current->fibril->state = TASK_RUNNING;
> + current->fibril->ti = current_thread_info();
> + }

Why do we need the "special" submission fibril?




> + for (i = 0; i < nr_inp; i++) {
> +
> + if (copy_from_user(&inp, &user_inp[i], sizeof(inp))) {
> + err = -EFAULT;
> + break;
> + }
> +
> + res = kmalloc(sizeof(struct asys_result), GFP_KERNEL);
> + if (res == NULL) {
> + err = -ENOMEM;
> + break;
> + }
> +
> + /* XXX kzalloc to init call.fibril.per_cpu, add helper */
> + call = kzalloc(sizeof(struct asys_call), GFP_KERNEL);
> + if (call == NULL) {
> + kfree(res);
> + err = -ENOMEM;
> + break;
> + }
> +
> + ti = alloc_thread_info(tsk);
> + if (ti == NULL) {
> + kfree(res);
> + kfree(call);
> + err = -ENOMEM;
> + break;
> + }
> +
> + err = asys_init_fibril(&call->fibril, ti, &inp);
> + if (err) {
> + kfree(res);
> + kfree(call);
> + free_thread_info(ti);
> + break;
> + }
> +
> + res->comp.cookie = inp.cookie;
> + call->result = res;
> + ti->task = current;
> +
> + sched_new_runnable_fibril(&call->fibril);
> + schedule();
> + }
> +
> + return i ? i : err;
> +}

Streamline error path (kfree(NULL) is OK):

err = -ENOMEM;
a = alloc();
b = alloc();
c = alloc();
if (!a || !b || !c)
goto error;
...
error:
kfree(c);
kfree(b);
kfree(a);
return err;

- Davide


-
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