From 45c5bf044a063a289fad6a53b8d27ce675d9c272 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sun, 10 Jul 2022 11:38:53 +0200
Subject: init/lib: implement "evil semaphores"

I started implementing native semaphores in the kernel, but then I've
realized that I can implement them in userland using pipes.

Thus, this hot garbage was born.
---
 src/init/tests/main.c      |  1 +
 src/init/tests/main.h      |  1 +
 src/init/tests/pipe.c      |  2 --
 src/init/tests/semaphore.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 72 insertions(+), 2 deletions(-)
 create mode 100644 src/init/tests/semaphore.c

(limited to 'src/init/tests')

diff --git a/src/init/tests/main.c b/src/init/tests/main.c
index f0845fe..9adb50c 100644
--- a/src/init/tests/main.c
+++ b/src/init/tests/main.c
@@ -146,5 +146,6 @@ void test_all(void) {
 	run_forked(test_memflag);
 	run_forked(test_malloc);
 	run_forked(test_pipe);
+	run_forked(test_semaphore);
 	run_forked(test_misc);
 }
diff --git a/src/init/tests/main.h b/src/init/tests/main.h
index 47c2507..ed11c5e 100644
--- a/src/init/tests/main.h
+++ b/src/init/tests/main.h
@@ -4,6 +4,7 @@ void stress_all(void);
 void test_all(void);
 
 void test_pipe(void);
+void test_semaphore(void);
 
 #ifdef TEST_MACROS
 
diff --git a/src/init/tests/pipe.c b/src/init/tests/pipe.c
index a980cb8..8e9d243 100644
--- a/src/init/tests/pipe.c
+++ b/src/init/tests/pipe.c
@@ -113,6 +113,4 @@ void test_pipe(void) {
 
 	// not a to.do detect when all processes that can read are stuck on writing to the pipe and vice versa
 	// it seems like linux just lets the process hang endlessly.
-
-	// TODO kill process that's waiting on a pipe
 }
diff --git a/src/init/tests/semaphore.c b/src/init/tests/semaphore.c
new file mode 100644
index 0000000..e542f0b
--- /dev/null
+++ b/src/init/tests/semaphore.c
@@ -0,0 +1,70 @@
+#define TEST_MACROS
+#include <init/lib/esemaphore.h>
+#include <init/stdlib.h>
+#include <init/tests/main.h>
+#include <shared/flags.h>
+#include <shared/syscalls.h>
+
+static void odd(struct evil_sem *sem1, struct evil_sem *sem2) {
+	printf("1");
+	esem_signal(sem1);
+
+	esem_wait(sem2);
+	printf("3");
+	esem_signal(sem1);
+
+	esem_wait(sem2);
+	printf("5");
+	esem_signal(sem1);
+}
+
+static void even(struct evil_sem *sem1, struct evil_sem *sem2) {
+	esem_wait(sem1);
+	printf("2");
+	esem_signal(sem2);
+
+	esem_wait(sem1);
+	printf("4");
+	esem_signal(sem2);
+
+	esem_wait(sem1);
+	printf("6");
+	esem_signal(sem2);
+}
+
+void test_semaphore(void) {
+	struct evil_sem *sem1, *sem2;
+
+	// TODO pipe-based test
+
+	sem1 = esem_new(0);
+	sem2 = esem_new(0);
+	assert(sem1 && sem2);
+	if (!_syscall_fork(0, NULL)) {
+		odd(sem1, sem2);
+		_syscall_exit(69);
+	} else {
+		even(sem1, sem2);
+		assert(_syscall_await() == 69);
+	}
+	esem_free(sem1);
+	esem_free(sem2);
+
+	printf("\n");
+
+	sem1 = esem_new(0);
+	sem2 = esem_new(0);
+	assert(sem1 && sem2);
+	if (!_syscall_fork(0, NULL)) {
+		even(sem1, sem2);
+		_syscall_exit(69);
+	} else {
+		odd(sem1, sem2);
+		assert(_syscall_await() == 69);
+		_syscall_await();
+	}
+	esem_free(sem1);
+	esem_free(sem2);
+
+	printf("\n");
+}
-- 
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