proc: more signal determinism, proper process exit in mt mode

kernel/libk/src/task/process.rs

@@ -324,13 +324,32 @@ impl Process {
     }
 
     /// Raises a signal for the specified process
-    pub fn raise_signal(self: &Arc<Self>, signal: Signal) {
-        let thread = self.inner.read().threads[0].clone();
-        thread.raise_signal(signal);
+    ///
+    /// If sender is Some(id) - signal was sent by some thread in some (possibly this) process.
+    /// If sender is None - signal was caused by some fault or some other non-deliberate cause.
+    pub fn raise_signal(self: &Arc<Self>, sender: Option<ThreadId>, signal: Signal) {
+        // If signal was raised by a thread within the process, consider the signal a
+        // "synchronous-like" and deliver it to the same thread that issued it.
+
+        let destination = {
+            let inner = self.inner.read();
+            if let Some(thread) = sender.and_then(|id| inner.threads.iter().find(|t| t.id == id)) {
+                // Behave like a "synchronous" signal, because a thread within a process asked to
+                // do something with the process itself. Make the requesting thread handle the
+                // signal.
+                thread.clone()
+            } else {
+                // Asynchronous signal not caused by any thread within the process, basically,
+                // any thread can handle it, but for determinism's sake, let it be the main one
+                inner.threads[0].clone()
+            }
+        };
+
+        destination.raise_signal(signal);
     }
 
     /// Raises a signal for the specified process group
-    pub fn signal_group(group_id: ProcessGroupId, signal: Signal) {
+    pub fn signal_group(sender: Option<ThreadId>, group_id: ProcessGroupId, signal: Signal) {
         MANAGER.for_each(|_, proc| {
             let inner = proc.inner.read();
             if !proc.has_exited() && inner.group_id == group_id {
@@ -342,7 +361,7 @@ impl Process {
                     signal
                 );
                 drop(inner);
-                proc.raise_signal(signal);
+                proc.raise_signal(sender, signal);
             }
         });
     }
@@ -398,6 +417,9 @@ impl Process {
         Ok(())
     }
 
+    /// Terminates all threads with the exclusion of `except`. This may be useful when a thread
+    /// wants the whole process to terminate: the asking thread itself must be exempt from this
+    /// termination, as it's the one doing the cleanup.
     pub async fn terminate_others(&self, except: ThreadId) {
         let mut inner = self.inner.write();
 
@@ -407,7 +429,9 @@ impl Process {
             }
 
             log::info!("Terminate thread {}", thread.id);
-            thread.terminate().await;
+            thread.terminate();
+            thread.exit.wait().await;
+            log::debug!("{} died", thread.id);
         }
 
         inner.retain_thread(except);

kernel/libk/src/task/sched.rs

@@ -82,6 +82,14 @@ impl CpuQueue {
             assert!(sched.in_queue);
             assert!(core::ptr::eq(self, sched.queue.unwrap()));
 
+            if thread.kill.is_signalled() {
+                sched.state = ThreadState::Terminated;
+                sched.in_queue = false;
+                sched.queue = None;
+                thread.set_terminated();
+                continue;
+            }
+
             match sched.state {
                 ThreadState::Ready => {
                     sched.state = ThreadState::Running;

kernel/libk/src/task/thread.rs

@@ -81,6 +81,7 @@ pub struct Thread {
     signal_queue: SegQueue<Signal>,
 
     pub exit: Arc<BoolEvent>,
+    pub kill: BoolEvent,
 
     /// CPU scheduling affinity mask
     pub affinity: ThreadAffinity,
@@ -135,6 +136,7 @@ impl Thread {
             inner: IrqSafeSpinlock::new(ThreadInner { signal_entry: None }),
             signal_queue: SegQueue::new(),
             exit: Arc::new(BoolEvent::new()),
+            kill: BoolEvent::new(),
 
             affinity: ThreadAffinity::any_cpu(),
         });
@@ -403,11 +405,16 @@ impl Thread {
         self.enqueue_to(queue);
     }
 
-    /// Requests thread termination and blocks until said thread finishes fully
-    pub async fn terminate(self: &Arc<Self>) {
-        // Will not abort the execution: called from another thread
-        self.dequeue(ThreadState::Terminated);
-        self.exit.wait().await;
+    /// Requests thread termination. This function only asks the thread to terminate, which will
+    /// happen the next time it's seen by the scheduler.
+    pub fn terminate(self: &Arc<Self>) {
+        // Will not abort the execution: called from another thread.
+        //
+        // Instead of dequeueing the thread, like done with a synchronous exit (when the thread
+        // exits on its own), instead, the thread needs to be **enqueued**, because we need to wake
+        // it up in order to make it die itself.
+        self.kill.signal_saturating();
+        self.enqueue();
     }
 
     /// Returns the current thread on the CPU.
@@ -496,7 +503,6 @@ impl CurrentThread {
         unreachable!()
     }
 
-    // TODO: test multithreaded process exit
     /// Terminate the parent process of the thread, including all other threads and the current
     /// thread itself
     pub fn exit_process(&self, code: ExitCode) -> ! {

kernel/libk/src/vfs/terminal.rs

@@ -156,7 +156,7 @@ impl<O: TerminalOutput> Terminal<O> {
                     self.output.notify_readers();
 
                     if let Some(group_id) = *self.input.signal_pgroup.read() {
-                        Process::signal_group(group_id, Signal::Interrupted);
+                        Process::signal_group(None, group_id, Signal::Interrupted);
                         self.input.ready_ring.notify_all();
                         return;
                     }

kernel/src/syscall/imp/sys_process.rs

@@ -205,8 +205,9 @@ pub(crate) fn set_signal_entry(ip: usize, sp: usize) {
 }
 
 pub(crate) fn send_signal(pid: ProcessId, signal: Signal) -> Result<(), Error> {
+    let thread = Thread::current();
     let target = Process::get(pid).ok_or(Error::DoesNotExist)?;
-    target.raise_signal(signal);
+    target.raise_signal(Some(thread.id), signal);
     Ok(())
 }
 
@@ -275,9 +276,11 @@ pub(crate) fn wait_thread(id: u32) -> Result<(), Error> {
     let this_thread = Thread::current();
     let process = this_thread.process();
 
-    block!(process.wait_for_thread(tid).await)??;
+    log::debug!("wait_thread({id})");
+    let result = block!(process.wait_for_thread(tid).await)?;
+    log::debug!("www -> {result:?}");
 
-    Ok(())
+    result
 }
 
 pub(crate) fn get_thread_option(option: &mut ThreadOption) -> Result<(), Error> {

lib/abi/src/process/mod.rs

@@ -166,3 +166,13 @@ impl ProgramArgumentInner {
         }
     }
 }
+
+impl Signal {
+    pub fn is_synchronous(&self) -> bool {
+        matches!(self, Self::MemoryAccessViolation)
+    }
+
+    pub fn is_handleable(&self) -> bool {
+        !matches!(self, Self::Killed)
+    }
+}

test.c

@@ -2,31 +2,18 @@
 #include <assert.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <stdlib.h>
 #include <sys/yggdrasil.h>
 
-static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
-
 static void *function(void *arg) {
-    pthread_barrier_t *barrier = (pthread_barrier_t *) arg;
-    printf("[child] waiting for parent\n");
-    pthread_barrier_wait(barrier);
-    printf("[child] barrier signalled!!\n");
+    abort();
     return NULL;
 }
 
 int main(int argc, const char **argv) {
     pthread_t thread;
-    pthread_barrier_t barrier;
-
-    pthread_barrier_init(&barrier, NULL, 2);
-
-    printf("[main] will make the child wait on a barrier\n");
-    assert(pthread_create(&thread, NULL, function, (void *) &barrier) == 0);
-
-    sleep(3);
-    pthread_barrier_wait(&barrier);
-    printf("[main] barrier signalled!!\n");
 
+    assert(pthread_create(&thread, NULL, function, (void *) NULL) == 0);
     pthread_join(thread, NULL);
 
     return 0;