libakerror/tests/err_threads_pool.c

#include "akerror.h"
#include "err_capture.h"
#include "err_threads.h"
#include <string.h>

/*
 * The error pool under contention.
 *
 * AKERR_ARRAY_ERROR is a fixed 128-slot array shared by every thread in the
 * process, and a slot is checked out by finding refcount == 0 and taking a
 * reference. Those two steps have to be one operation: a scan that returned an
 * unclaimed slot would hand the same one to every thread that scanned before
 * the first of them incremented the count, and each would then format its own
 * error into the same buffers. That failure is invisible to a single-threaded
 * test and produces a garbled message rather than a crash, so this test asserts
 * exclusivity directly.
 *
 * akerr_slot_owner[] (see err_threads.h) is the test's own record of who holds
 * which slot, kept with atomics. Every check-out claims its slot and every
 * release drops the claim; a slot handed to two threads at once is caught by
 * the claim failing, whether or not the resulting message is garbled.
 *
 * Each thread also asserts that the error it raised is the error it handles,
 * message and all. That is the same property from the other end: a context
 * cannot be exclusively ours if another thread's text shows up in it.
 */

#define ITERATIONS 2000

/* Raise an error and take ownership of whatever slot it came from. */
static akerr_ErrorContext AKERR_NOIGNORE *boom(akerr_ThreadArg *arg)
{
    PREPARE_ERROR(e);

    FAIL(e, AKERR_VALUE, "raised by thread %d", arg->id);
    AKERR_TCHECK(arg, akerr_slot_claim(e->arrayid, arg->id) == 0);
    return e;
}

static akerr_ErrorContext AKERR_NOIGNORE *ignorable(akerr_ThreadArg *arg)
{
    PREPARE_ERROR(e);

    FAIL_RETURN(e, AKERR_IO, "ignored by thread %d", arg->id);
}

/* One raise -> catch -> handle cycle, exclusively owned from end to end. */
static void one_cycle(akerr_ThreadArg *arg)
{
    char expected[64];
    PREPARE_ERROR(e);

    snprintf(expected, sizeof(expected), "raised by thread %d", arg->id);
    ATTEMPT {
	CATCH(e, boom(arg));
    } CLEANUP {
    } PROCESS(e) {
	/* case 0: the error we just raised came back clean, which can only
	 * mean another thread wrote over this context. */
	int error_was_lost = 1;
	AKERR_TCHECK(arg, error_was_lost == 0);
    } HANDLE(e, AKERR_VALUE) {
	AKERR_TCHECK(arg, akerr_slot_holder(e->arrayid) == arg->id);
	AKERR_TCHECK(arg, strcmp(e->message, expected) == 0);
	AKERR_TCHECK(arg, strstr(e->stacktracebuf, expected) != NULL);
	/* Give the slot up before FINISH releases the context: the other order
	 * hands it back to the pool while this thread still claims it. */
	akerr_slot_drop(e->arrayid);
    } FINISH_NORETURN(e);
}

/* The same property against the raw pool API, with no macros in between. */
static void one_checkout(akerr_ThreadArg *arg)
{
    akerr_ErrorContext *e = akerr_next_error();

    AKERR_TCHECK(arg, e != NULL);
    if ( e == NULL ) {
	return;
    }
    /* The context arrives already holding its reference. */
    AKERR_TCHECK(arg, e->refcount == 1);
    AKERR_TCHECK(arg, akerr_slot_claim(e->arrayid, arg->id) == 0);
    AKERR_TCHECK(arg, akerr_slot_holder(e->arrayid) == arg->id);
    akerr_slot_drop(e->arrayid);
    RELEASE_ERROR(e);
    AKERR_TCHECK(arg, e == NULL);
}

static void *pool_body(void *raw)
{
    akerr_ThreadArg *arg = raw;
    char expected[64];

    snprintf(expected, sizeof(expected), "ignored by thread %d", arg->id);
    pthread_barrier_wait(arg->barrier);

    for ( int i = 0; i < ITERATIONS; i++ ) {
	one_cycle(arg);
	one_checkout(arg);
    }

    /* An ignored error is a fact about the thread that ignored it: each thread
     * must see its own, not the last one any thread swallowed. */
    IGNORE(ignorable(arg));
    AKERR_TCHECK(arg, __akerr_last_ignored != NULL);
    if ( __akerr_last_ignored != NULL ) {
	AKERR_TCHECK(arg, __akerr_last_ignored->status == AKERR_IO);
	AKERR_TCHECK(arg, strcmp(__akerr_last_ignored->message, expected) == 0);
    }
    /* IGNORE keeps the reference by design; hand it back so the pool is empty
     * at the end of the test. */
    RELEASE_ERROR(__akerr_last_ignored);

    return NULL;
}

int main(void)
{
    akerr_log_method = &akerr_thread_logger;
    akerr_init();
    AKERR_CHECK(akerr_slots_in_use() == 0);

    int failures = akerr_run_threads(&pool_body);
    AKERR_CHECK(failures == 0);

    /* Every context went back to the pool, and every claim was dropped. */
    AKERR_CHECK(akerr_slots_in_use() == 0);
    for ( int i = 0; i < AKERR_MAX_ARRAY_ERROR; i++ ) {
	AKERR_CHECK(akerr_slot_holder(i) == 0);
    }
    /* Each thread's IGNORE reported through the log method. */
    AKERR_CHECK(akerr_thread_logs() >= AKERR_TEST_THREADS);

    fprintf(stderr, "err_threads_pool ok (%d threads x %d cycles)\n",
	    AKERR_TEST_THREADS, ITERATIONS);
    return 0;
}