cpu/native: fix lockup on libucontext

maribu · crasbe · maribu · commit 87af1a4b583d · 2025-11-26T12:43:09.000+01:00
The `setcontext()` implementation of glibc does restore the signal mask to the target thread during the switch, libucontext [does not][1] [1]: https://man.archlinux.org/man/libucontext.3.en#CAVEATS Instead, we just manually enable signals again just before the call to `setcontext()`. With this, tests like `tests/core/mutex_canel` or `tests/core/irq` now pass on `native64` when using libucontext. Co-authored-by: crasbe <crasbe@gmail.com>
diff --git a/cpu/native/cpu.c b/cpu/native/cpu.c
@@ -78,6 +78,17 @@ void _isr_switch_to_user(void) {
     /* Now we want to go to _native_isr_leave before resuming execution at _native_user_fptr. */
     _context_set_fptr(context, (uintptr_t)_native_isr_leave);
 
+    /* libucontext does not restore signal mask on setcontext() [1], so we
+     * need to enable signals again to not get locked up
+     *
+     * [1]: https://man.archlinux.org/man/libucontext.3.en#CAVEATS
+     */
+    if (IS_ACTIVE(USE_LIBUCONTEXT)) {
+        if (sigprocmask(SIG_SETMASK, &_native_sig_set, NULL) == -1) {
+            err(EXIT_FAILURE, "irq_enable: sigprocmask");
+        }
+    }
+
     if (setcontext(context) == -1) {
         err(EXIT_FAILURE, "_isr_schedule_and_switch: setcontext");
     }
diff --git a/cpu/native/include/native_internal.h b/cpu/native/include/native_internal.h
@@ -86,6 +86,12 @@ void native_cpu_init(void);
  */
 extern volatile bool _native_interrupts_enabled;
 
+/**
+ * @brief Signal set during "IRQs enabled"
+ * @internal
+ */
+extern sigset_t _native_sig_set;
+
 /**
  * @brief Pipe yielding signals
  * @private
diff --git a/cpu/native/irq.c b/cpu/native/irq.c
@@ -40,7 +40,7 @@ ucontext_t *_native_current_context = NULL;
 
 volatile uintptr_t _native_user_fptr;
 
-static sigset_t _native_sig_set;
+sigset_t _native_sig_set;
 static sigset_t _native_sig_set_dint;
 volatile int _native_pending_signals;
 int _signal_pipe_fd[2];
