From 6c4f56723c24bbf2f21c5a29f81b30917f9144e1 Mon Sep 17 00:00:00 2001
From: Ruize Tang <1466040111@qq.com>
Date: Mon, 11 Nov 2024 20:41:56 +0800
Subject: [PATCH] Fix futex lost wakeup

---
 kernel/src/process/posix_thread/futex.rs |   9 +-
 test/apps/pthread/pthread_signal_test.c  | 109 +++++++++++++++++++++++
 2 files changed, 115 insertions(+), 3 deletions(-)
 create mode 100644 test/apps/pthread/pthread_signal_test.c

diff --git a/kernel/src/process/posix_thread/futex.rs b/kernel/src/process/posix_thread/futex.rs
index 26af862c..c44e9beb 100644
--- a/kernel/src/process/posix_thread/futex.rs
+++ b/kernel/src/process/posix_thread/futex.rs
@@ -253,7 +253,9 @@ impl FutexBucket {
             }
 
             let item = item_cursor.remove().unwrap();
-            item.wake();
+            if !item.wake() {
+                continue;
+            }
             count += 1;
         }
 
@@ -323,8 +325,9 @@ impl FutexItem {
         (futex_item, waiter)
     }
 
-    pub fn wake(&self) {
-        self.waker.wake_up();
+    #[must_use]
+    pub fn wake(&self) -> bool {
+        self.waker.wake_up()
     }
 
     pub fn match_up(&self, another: &Self) -> bool {
diff --git a/test/apps/pthread/pthread_signal_test.c b/test/apps/pthread/pthread_signal_test.c
new file mode 100644
index 00000000..c84c4206
--- /dev/null
+++ b/test/apps/pthread/pthread_signal_test.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: MPL-2.0
+// A regression test for the futex lost wakeup bug fixed in https://github.com/asterinas/asterinas/pull/1642
+
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdatomic.h>
+
+pthread_mutex_t mutex;
+atomic_int sync_flag = ATOMIC_VAR_INIT(0); // Atomic flag for synchronization
+
+// Signal handler for SIGUSR1
+void signal_handler(int signum)
+{
+	atomic_store(&sync_flag, 2);
+}
+
+// Thread function that tries to lock the mutex and waits if it is locked
+void *thread_function(void *arg)
+{
+	printf("Thread: Trying to lock mutex...\n");
+
+	// Set the atomic flag to signal the main thread
+	atomic_store(&sync_flag, 1);
+
+	// Try to lock the mutex
+	pthread_mutex_lock(&mutex);
+	printf("Thread: Got the mutex!\n");
+
+	printf("Thread: Exiting.\n");
+	pthread_mutex_unlock(&mutex);
+
+	// Set the atomic flag to signal the main thread
+	atomic_store(&sync_flag, 3);
+	return NULL;
+}
+
+int main()
+{
+	pthread_t thread;
+
+	// Initialize mutex
+	if (pthread_mutex_init(&mutex, NULL) != 0) {
+		perror("Mutex initialization failed");
+		return -1;
+	}
+
+	// Set up signal handler for SIGUSR1
+	struct sigaction sa;
+	sa.sa_handler = signal_handler;
+	sa.sa_flags = 0;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(SIGUSR1, &sa, NULL) == -1) {
+		perror("sigaction failed");
+		return -1;
+	}
+
+	// Main thread locks the mutex
+	pthread_mutex_lock(&mutex);
+	printf("Main thread: Mutex locked.\n");
+
+	// Create the second thread
+	if (pthread_create(&thread, NULL, thread_function, NULL) != 0) {
+		perror("Thread creation failed");
+		return -1;
+	}
+
+	// Detach the thread to allow it to run independently
+	if (pthread_detach(thread) != 0) {
+		perror("Thread detachment failed");
+		return -1;
+	}
+
+	// Wait for the second thread to prepare
+	while (atomic_load(&sync_flag) != 1) {
+	}
+	sleep(1);
+
+	// Send signal to the second thread
+	pthread_kill(thread, SIGUSR1);
+	printf("Main thread: Signal sent to the thread.\n");
+
+	// Wait for the second thread to process signal
+	while (atomic_load(&sync_flag) != 2) {
+	}
+	sleep(1);
+
+	// Unlock the mutex
+	pthread_mutex_unlock(&mutex);
+	printf("Main thread: Mutex unlocked.\n");
+
+	// Wait for the second thread to exit
+	int count = 3;
+	while (atomic_load(&sync_flag) != 3 && count--) {
+		sleep(1);
+	}
+	if (atomic_load(&sync_flag) != 3) {
+		printf("ERROR: Thread does not exit after timeout.\n");
+		exit(EXIT_FAILURE);
+	}
+
+	// Destroy mutex
+	pthread_mutex_destroy(&mutex);
+
+	printf("All tests passed.\n");
+	return 0;
+}