[PATCH v2 2/6] eal: add thread lifetime management

[Dmitry Kozlyuk]

2022-06-21 11:51 (UTC-0700), Tyler Retzlaff:
> > > +int
> > > +rte_thread_join(rte_thread_t thread_id, unsigned long *value_ptr)
> > > +{
> > > +	int ret = 0;
> > > +	void *res = NULL;
> > > +	void **pres = NULL;
> > > +
> > > +	if (value_ptr != NULL)
> > > +		pres = &res;
> > > +
> > > +	ret = pthread_join((pthread_t)thread_id.opaque_id, pres);
> > > +	if (ret != 0) {
> > > +		RTE_LOG(DEBUG, EAL, "pthread_join failed\n");
> > > +		return ret;
> > > +	}
> > > +
> > > +	if (value_ptr != NULL && *pres != NULL)
> > > +		*value_ptr = *(unsigned long *)(*pres);
> > > +
> > > +	return 0;
> > > +}  
> > 
> > What makes *pres == NULL special?  
> 
> it's not clear what you mean, can you explain? maybe there is some
> context i am missing from the original patch series?

There's no previous context.
After ptread_join(), *pres holds the return value of the thread routine.
You only assign *value_ptr if value_ptr is not NULL (obviously correct)
and if *pres != NULL, that is, if the thread returned a non-NULL value.
But this value is opaque, why do you filter NULL?
Perhaps you meant if (pres != NULL), no dereference?

> > > +int
> > > +rte_thread_create(rte_thread_t *thread_id,
> > > +		  const rte_thread_attr_t *thread_attr,
> > > +		  rte_thread_func thread_func, void *args)
> > > +{
> > > +	int ret = 0;
> > > +	DWORD tid;
> > > +	HANDLE thread_handle = NULL;
> > > +	GROUP_AFFINITY thread_affinity;
> > > +	struct thread_routine_ctx *ctx = NULL;
> > > +
> > > +	ctx = calloc(1, sizeof(*ctx));
> > > +	if (ctx == NULL) {
> > > +		RTE_LOG(DEBUG, EAL, "Insufficient memory for thread context allocations\n");
> > > +		ret = ENOMEM;
> > > +		goto cleanup;
> > > +	}
> > > +	ctx->routine_args = args;
> > > +	ctx->thread_func = thread_func;
> > > +
> > > +	thread_handle = CreateThread(NULL, 0, thread_func_wrapper, ctx,
> > > +		CREATE_SUSPENDED, &tid);
> > > +	if (thread_handle == NULL) {
> > > +		ret = thread_log_last_error("CreateThread()");
> > > +		free(ctx);
> > > +		goto cleanup;  
> > 
> > Missing `free(ctx)` from other error paths below.  
> 
> beyond this point free(ctx) will happen in thread_func_wrapper. i will
> add a comment to make it clear.

Not if you exit before ResumeThread()
and thread_func_wrapper() will never execute to call free().