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mruby-task: fix crash by setting vmexec flag during task execution

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Fix task termination crash caused by fiber_terminate freeing task
context resources. When a task completes, the VM would call
fiber_terminate which frees cibase/stbase, then next resume attempt
crashes dereferencing NULL pointers.

Solution unifies task and fiber lifecycle management:
- Set vmexec flag before calling mrb_vm_exec to prevent fiber_terminate
  from being called during normal task completion
- Save proc/pc to local variables to avoid CI_PROC_SET macro corruption
- Add termination check in mrb_task_free to prevent double-free

Tasks now follow the same execution pattern as Fiber, leveraging
VM's built-in context management.

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2025-10-09 10:58:23 +09:00
parent 8eb275b665
commit 61f99385ba
1 changed files with 19 additions and 7 deletions
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mrbgems/mruby-task/src/task.c
+19 -7
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@@ -54,12 +54,14 @@ mrb_task_free(mrb_state *mrb, void *ptr)
/* Unregister from GC protection */
mrb_gc_unregister(mrb, t->self);
/* Free context resources */
if (t->c.stbase) {
mrb_free(mrb, t->c.stbase);
}
if (t->c.cibase) {
mrb_free(mrb, t->c.cibase);
/* Free context resources only if not already terminated by fiber_terminate */
if (t->c.status != MRB_FIBER_TERMINATED) {
if (t->c.stbase) {
mrb_free(mrb, t->c.stbase);
}
if (t->c.cibase) {
mrb_free(mrb, t->c.cibase);
}
}
/* Free the task structure itself */
mrb_free(mrb, t);
@@ -377,8 +379,18 @@ mrb_tasks_run(mrb_state *mrb)
/* Set status to RUNNING so VM can transition it properly */
t->c.status = MRB_FIBER_RUNNING;
/* Save proc and PC to locals before calling mrb_vm_exec */
const struct RProc *proc = t->c.ci->proc;
const mrb_code *pc = t->c.ci->pc;
/* Set vmexec flag to prevent fiber_terminate from being called */
t->c.vmexec = TRUE;
/* Execute task - PC is saved in ci->pc from previous run */
t->result = mrb_vm_exec(mrb, t->c.ci->proc, t->c.ci->pc);
t->result = mrb_vm_exec(mrb, proc, pc);
/* Clear vmexec flag */
t->c.vmexec = FALSE;
/* Restore context */
mrb->c = prev_c;