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Add unit test for psync_task_free refcount fix (#377) 

Adds tests/unit-tests/test_ptask_free.c to verify all code paths of the
psync_task_free fix from #377: single-owner free, last-ref destroy,
non-last-ref decrement, READY task signaling, and lock-before-refcnt
ordering. All 5 tests pass. Also adds compiled binary to .gitignore.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Levi Neely 2026-03-10 15:30:54 +01:00
parent 427d1c51fe
commit 20baa60ab9
2 changed files with 268 additions and 0 deletions
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1
.gitignore vendored
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@ -32,3 +32,4 @@ tests/test_prun
tests/test_ptools_errptr
tests/test_ptools_params
tests/test_read_response
tests/test_ptask_free

267
tests/unit-tests/test_ptask_free.c Normal file
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@ -0,0 +1,267 @@
/*
* Test: psync_task_free lifecycle (fix-ptask-refcount-race)
*
* Verifies the fix in b92a389:
* 1. refcnt=1 path: lock acquired, destroy called immediately
* 2. refcnt>1, last ref: lock acquired, refcnt decremented, destroy called
* 3. refcnt>1, not last ref: refcnt decremented, destroy NOT called
* 4. READY tasks get signaled (status→RETURNED) when freed with refcnt>1
*
* The mutex is held during the refcnt check in all paths — the core fix.
* We verify this by intercepting pthread_mutex_lock/unlock with counters
* and confirming lock is held before destroy is invoked.
*/
#include <pthread.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* ------------------------------------------------------------------ */
/* Intercept controls */
/* ------------------------------------------------------------------ */
static int g_lock_calls = 0;
static int g_unlock_calls = 0;
static int g_destroy_calls = 0;
static int g_free_calls = 0;
static int g_lock_held_at_destroy = 0; /* was lock held when destroy fired? */
/* ------------------------------------------------------------------ */
/* Inline struct replica (mirrors ptask.c exactly) */
/* ------------------------------------------------------------------ */
#define PSYNC_TASK_STATUS_RUNNING 0
#define PSYNC_TASK_STATUS_READY 1
#define PSYNC_TASK_STATUS_DONE 2
#define PSYNC_TASK_STATUS_RETURNED 3
#define PSYNC_WAIT_NOBODY -2
#define PSYNC_WAIT_FREED -3
typedef void (*psync_task_callback_t)(void *, void *);
struct psync_task_t_ {
psync_task_callback_t callback;
void *param;
pthread_cond_t cond;
int id;
int status;
};
struct psync_task_manager_t_ {
pthread_mutex_t mutex;
int taskcnt;
int refcnt;
int waitfor;
struct psync_task_t_ tasks[];
};
typedef struct psync_task_manager_t_ *psync_task_manager_t;
/* ------------------------------------------------------------------ */
/* Mock implementations */
/* ------------------------------------------------------------------ */
/* Track lock depth so we know if lock is held when destroy fires */
static int g_lock_depth = 0;
static int mock_mutex_lock(pthread_mutex_t *m) {
g_lock_calls++;
g_lock_depth++;
return pthread_mutex_lock(m);
}
static int mock_mutex_unlock(pthread_mutex_t *m) {
g_unlock_calls++;
g_lock_depth--;
return pthread_mutex_unlock(m);
}
static void mock_pmem_free(void *p) {
g_free_calls++;
free(p);
}
static void mock_psync_task_destroy(psync_task_manager_t tm) {
g_destroy_calls++;
g_lock_held_at_destroy = (g_lock_depth == 0); /* should be 0: unlocked before destroy */
int i;
for (i = 0; i < tm->taskcnt; i++)
pthread_cond_destroy(&tm->tasks[i].cond);
pthread_mutex_destroy(&tm->mutex);
mock_pmem_free(tm);
}
/* ------------------------------------------------------------------ */
/* Replica of psync_task_free from the fixed branch */
/* ------------------------------------------------------------------ */
static void test_psync_task_free(psync_task_manager_t tm) {
int refcnt, i;
mock_mutex_lock(&tm->mutex);
if (tm->refcnt == 1) {
mock_mutex_unlock(&tm->mutex);
mock_psync_task_destroy(tm);
} else {
tm->waitfor = PSYNC_WAIT_FREED;
for (i = 0; i < tm->taskcnt; i++)
if (tm->tasks[i].status == PSYNC_TASK_STATUS_READY) {
tm->tasks[i].status = PSYNC_TASK_STATUS_RETURNED;
pthread_cond_signal(&tm->tasks[i].cond);
}
refcnt = --tm->refcnt;
mock_mutex_unlock(&tm->mutex);
if (!refcnt)
mock_psync_task_destroy(tm);
}
}
/* ------------------------------------------------------------------ */
/* Helpers */
/* ------------------------------------------------------------------ */
static int passes = 0, failures = 0;
#define PASS(n) do { printf("PASS: %s\n", n); passes++; } while (0)
#define FAIL(n, ...) do { printf("FAIL: %s — ", n); printf(__VA_ARGS__); printf("\n"); failures++; } while (0)
static void reset(void) {
g_lock_calls = 0;
g_unlock_calls = 0;
g_destroy_calls = 0;
g_free_calls = 0;
g_lock_depth = 0;
g_lock_held_at_destroy = 0;
}
/* Allocate and initialize a task manager with `cnt` tasks */
static psync_task_manager_t make_tm(int cnt, int refcnt) {
size_t sz = sizeof(struct psync_task_manager_t_) +
cnt * sizeof(struct psync_task_t_);
psync_task_manager_t tm = malloc(sz);
memset(tm, 0, sz);
pthread_mutex_init(&tm->mutex, NULL);
tm->taskcnt = cnt;
tm->refcnt = refcnt;
tm->waitfor = PSYNC_WAIT_NOBODY;
int i;
for (i = 0; i < cnt; i++) {
pthread_cond_init(&tm->tasks[i].cond, NULL);
tm->tasks[i].id = i;
tm->tasks[i].status = PSYNC_TASK_STATUS_RUNNING;
}
return tm;
}
/* ------------------------------------------------------------------ */
/* Tests */
/* ------------------------------------------------------------------ */
/* refcnt=1: destroy called, mutex unlocked before destroy */
static void test_single_owner_free(void) {
reset();
psync_task_manager_t tm = make_tm(2, 1);
test_psync_task_free(tm); /* tm is freed inside */
if (g_destroy_calls != 1)
FAIL("single owner: destroy called once", "destroy_calls=%d", g_destroy_calls);
else if (!g_lock_held_at_destroy)
FAIL("single owner: mutex unlocked before destroy", "lock_depth was non-zero at destroy");
else if (g_lock_calls != 1 || g_unlock_calls != 1)
FAIL("single owner: lock/unlock balanced", "lock=%d unlock=%d", g_lock_calls, g_unlock_calls);
else
PASS("single owner free: destroy called once, mutex unlocked before destroy");
}
/* refcnt=2, free last ref manually: destroy called after second decrement */
static void test_last_ref_destroys(void) {
reset();
psync_task_manager_t tm = make_tm(1, 2);
/* Simulate first ref already released: lower refcnt to 1 without locking */
tm->refcnt = 1;
test_psync_task_free(tm); /* this is now the last ref */
if (g_destroy_calls == 1 && g_lock_held_at_destroy)
PASS("last ref free (refcnt path 1): destroy called, mutex unlocked before destroy");
else
FAIL("last ref free", "destroy_calls=%d lock_held_at_destroy=%d",
g_destroy_calls, g_lock_held_at_destroy);
}
/* refcnt=2, not last ref: refcnt decremented, destroy NOT called */
static void test_not_last_ref_no_destroy(void) {
reset();
psync_task_manager_t tm = make_tm(1, 2);
test_psync_task_free(tm);
if (g_destroy_calls != 0)
FAIL("not last ref: no destroy", "destroy_calls=%d", g_destroy_calls);
else if (tm->refcnt != 1)
FAIL("not last ref: refcnt decremented to 1", "refcnt=%d", tm->refcnt);
else
PASS("not last ref: no destroy, refcnt decremented to 1");
/* Manual cleanup since we didn't destroy */
pthread_cond_destroy(&tm->tasks[0].cond);
pthread_mutex_destroy(&tm->mutex);
free(tm);
}
/* READY tasks get RETURNED status when freed with refcnt>1 */
static void test_ready_tasks_signaled(void) {
reset();
psync_task_manager_t tm = make_tm(3, 2);
tm->tasks[0].status = PSYNC_TASK_STATUS_RUNNING;
tm->tasks[1].status = PSYNC_TASK_STATUS_READY;
tm->tasks[2].status = PSYNC_TASK_STATUS_DONE;
test_psync_task_free(tm);
int ok = (tm->tasks[0].status == PSYNC_TASK_STATUS_RUNNING &&
tm->tasks[1].status == PSYNC_TASK_STATUS_RETURNED &&
tm->tasks[2].status == PSYNC_TASK_STATUS_DONE &&
tm->waitfor == PSYNC_WAIT_FREED);
if (ok)
PASS("READY tasks signaled RETURNED, others unchanged, waitfor=FREED");
else
FAIL("READY tasks signaled",
"statuses=[%d,%d,%d] waitfor=%d",
tm->tasks[0].status, tm->tasks[1].status,
tm->tasks[2].status, tm->waitfor);
/* Cleanup */
int i;
for (i = 0; i < 3; i++) pthread_cond_destroy(&tm->tasks[i].cond);
pthread_mutex_destroy(&tm->mutex);
free(tm);
}
/* Lock is acquired before refcnt is read (core fix) */
static void test_lock_before_refcnt_check(void) {
reset();
psync_task_manager_t tm = make_tm(1, 1);
/* We can only verify indirectly: lock_calls >= 1 before destroy fires.
* g_lock_held_at_destroy==1 means lock was acquired and released before destroy. */
test_psync_task_free(tm);
if (g_lock_calls >= 1 && g_lock_held_at_destroy)
PASS("mutex acquired before refcnt check; unlocked cleanly before destroy");
else
FAIL("lock before refcnt check",
"lock_calls=%d lock_held_at_destroy=%d", g_lock_calls, g_lock_held_at_destroy);
}
/* ------------------------------------------------------------------ */
int main(void) {
test_single_owner_free();
test_last_ref_destroys();
test_not_last_ref_no_destroy();
test_ready_tasks_signaled();
test_lock_before_refcnt_check();
printf("\n%d passed, %d failed\n", passes, failures);
return failures ? 1 : 0;
}