Don't double-clear is_pending flag.

src/context/signal.rs

@@ -57,6 +57,7 @@ pub fn signal_handler() {
     // TODO: thumbs_down
     let Some((thread_ctl, proc_ctl, st)) = context.sigcontrol() else {
         // Discard signal if sigcontrol is unset.
+        log::trace!("no sigcontrol, returning");
         return;
     };
     let control_flags = SigcontrolFlags::from_bits_retain(thread_ctl.control_flags.load(Ordering::Acquire));
@@ -64,15 +65,20 @@ pub fn signal_handler() {
     if control_flags.contains(SigcontrolFlags::INHIBIT_DELIVERY) {
         // Signals are inhibited to protect critical sections inside libc, but this code will run
         // every time the context is switched to.
+        log::trace!("Inhibiting delivery, returning");
         return;
     }
 
     if !core::mem::take(&mut st.is_pending) {
+        log::trace!("Not pending, returning");
         return;
     }
 
+    let sigh_instr_ptr = st.user_handler.get();
+
     let Some(regs) = context.regs_mut() else {
         // TODO: is this even reachable?
+        log::trace!("No registers, returning");
         return;
     };
 
@@ -82,6 +88,8 @@ pub fn signal_handler() {
     let scratch_a = regs.scratch.a();
     let scratch_b = regs.scratch.b();
 
+    regs.set_instr_pointer(sigh_instr_ptr);
+
     let (thread_ctl, _, _) = context.sigcontrol()
         .expect("cannot have been unset while holding the lock");
 

src/context/switch.rs

@@ -50,7 +50,7 @@ unsafe fn update_runnable(context: &mut Context, cpu_id: LogicalCpuId) -> Update
 
     // Switch to context if it needs to run
     if context.status.is_runnable() {
-        UpdateResult::CanSwitch { signal: context.sig.as_mut().map_or(false, |s| mem::take(&mut s.is_pending)) }
+        UpdateResult::CanSwitch { signal: context.sig.as_mut().map_or(false, |s| s.is_pending) }
     } else {
         UpdateResult::Skip
     }