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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Copyright (C) 2026 Richard Qin */
/*
* test_mutex — self-tests for the Mutex sleeping lock.
*
* Coverage:
* - basic lock/unlock single-thread
* - try_lock when free and when held
* - mutual exclusion across kthreads (no lost increments)
* - FIFO wake order (A acquires, B/C queue; release lets B in then C)
*/
#include <lume/selftest.h>
#include <lume/mutex.h>
#include <lume/task.h>
#include <lume/sched.h>
#include <lume/kprintf.h>
extern TaskControlBlock* kthread_create(const char* name,
void (*entry)(void*), void* arg,
uint8 priority);
extern void task_exit(int code);
/* ------------------------------------------------------------------ */
/* Test 1: basic lock/unlock */
/* ------------------------------------------------------------------ */
static void test_basic()
{
st_begin("mutex: basic lock/unlock");
Mutex m;
m.init("test_basic");
ST_ASSERT(!m.is_locked());
m.lock();
ST_ASSERT(m.is_locked());
ST_ASSERT(m.is_owned_by_current());
m.unlock();
ST_ASSERT(!m.is_locked());
st_pass();
}
/* ------------------------------------------------------------------ */
/* Test 2: try_lock */
/* ------------------------------------------------------------------ */
static void test_trylock()
{
st_begin("mutex: try_lock");
Mutex m;
m.init("test_trylock");
ST_ASSERT(m.try_lock() == true);
ST_ASSERT(m.is_locked());
/* A second try_lock from the same task: since owner == current,
* we still return false (try_lock is non-recursive). */
ST_ASSERT(m.try_lock() == false);
m.unlock();
ST_ASSERT(!m.is_locked());
ST_ASSERT(m.try_lock() == true);
m.unlock();
st_pass();
}
/* ------------------------------------------------------------------ */
/* Test 3: mutual exclusion across kthreads */
/* ------------------------------------------------------------------ */
static Mutex g_mut;
static volatile int32 g_counter = 0;
static volatile int32 g_done = 0;
static constexpr int32 kIters = 200;
static void mutex_worker(void*)
{
for (int i = 0; i < kIters; i++) {
g_mut.lock();
int32 v = g_counter;
/* Yield inside the critical section to expose missing mutex.
* If the mutex were broken we'd see lost increments. */
sched_yield();
g_counter = v + 1;
g_mut.unlock();
}
__sync_fetch_and_add(&g_done, 1);
task_exit(0);
}
static void test_mutual_exclusion()
{
st_begin("mutex: mutual exclusion (2 workers)");
g_mut.init("test_mutex_mx");
g_counter = 0;
g_done = 0;
kthread_create("mut_w1", mutex_worker, nullptr, 0);
kthread_create("mut_w2", mutex_worker, nullptr, 0);
/* Spin-yield until both workers finish. */
while (g_done < 2) {
sched_yield();
}
ST_ASSERT_EQ(g_counter, 2 * kIters);
ST_ASSERT(!g_mut.is_locked());
st_pass();
}
/* ------------------------------------------------------------------ */
/* Test 4: FIFO wake order */
/* ------------------------------------------------------------------ */
static Mutex g_fifo_mut;
static volatile int32 g_fifo_seq = 0; // monotonically increases
static volatile int32 g_fifo_order[3]; // order each worker observed
static volatile int32 g_fifo_done = 0;
static void fifo_worker(void* arg)
{
int slot = static_cast<int>(reinterpret_cast<uint64>(arg));
g_fifo_mut.lock();
g_fifo_order[slot] = __sync_fetch_and_add(&g_fifo_seq, 1);
g_fifo_mut.unlock();
__sync_fetch_and_add(&g_fifo_done, 1);
task_exit(0);
}
static void test_fifo_order()
{
st_begin("mutex: FIFO wake order (3 waiters)");
g_fifo_mut.init("test_mutex_fifo");
g_fifo_seq = 0;
g_fifo_done = 0;
g_fifo_order[0] = g_fifo_order[1] = g_fifo_order[2] = -1;
/* Main grabs the lock first so workers will queue up behind. */
g_fifo_mut.lock();
/* Spawn workers in deterministic order. After each create() yield
* once so the new thread reaches mutex.lock() and enqueues itself
* before we spawn the next one. */
kthread_create("fifo_A", fifo_worker, reinterpret_cast<void*>(0), 0);
sched_yield();
kthread_create("fifo_B", fifo_worker, reinterpret_cast<void*>(1), 0);
sched_yield();
kthread_create("fifo_C", fifo_worker, reinterpret_cast<void*>(2), 0);
sched_yield();
/* Release: A should fire next, then B, then C. */
g_fifo_mut.unlock();
while (g_fifo_done < 3) {
sched_yield();
}
ST_ASSERT_EQ(g_fifo_order[0], 0);
ST_ASSERT_EQ(g_fifo_order[1], 1);
ST_ASSERT_EQ(g_fifo_order[2], 2);
st_pass();
}
/* ------------------------------------------------------------------ */
/* Entry */
/* ------------------------------------------------------------------ */
void selftest_mutex()
{
test_basic();
test_trylock();
test_mutual_exclusion();
test_fifo_order();
}
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