Re: regression in multi-threaded git-pack-index

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 19, 2013, 17:58 UTC
Message-ID: <7v1ubbjmq7.fsf@alter.siamese.dyndns.org>
In-Reply-To: <87obef2wut.fsf@pctrast.inf.ethz.ch>

Thomas Rast <trast@student.ethz.ch> writes:

Show 6 quoted lines

> Actually scratch that again.  It *is* a stack overflow, except that this
> is a thread stack, for which the OS X defaults are 512kB apparently, as
> opposed to 2MB on linux.
> ...
> And indeed the following patch fixes it.  Sounds like the delta
> unpacking needs a rewrite to support stackless operation.  Sigh.

Yikes.  Thanks for digging it to the bottom.

I am not sure if I want to carry this patch in its current form, though. As this episode demonstrates, no default is good enough for everybody, and I am not sure if a configuration variable is a good way to go, either.

Show 24 quoted lines

>
> diff --git i/builtin/index-pack.c w/builtin/index-pack.c
> index 6be99e2..f73291f 100644
> --- i/builtin/index-pack.c
> +++ w/builtin/index-pack.c
> @@ -1075,13 +1075,17 @@ static void resolve_deltas(void)
>  	nr_dispatched = 0;
>  	if (nr_threads > 1 || getenv("GIT_FORCE_THREADS")) {
>  		init_thread();
> +		pthread_attr_t attr;
> +		pthread_attr_init(&attr);
> +		pthread_attr_setstacksize(&attr, 2*1024*1024);
>  		for (i = 0; i < nr_threads; i++) {
> -			int ret = pthread_create(&thread_data[i].thread, NULL,
> +			int ret = pthread_create(&thread_data[i].thread, &attr,
>  						 threaded_second_pass, thread_data + i);
>  			if (ret)
>  				die(_("unable to create thread: %s"),
>  				    strerror(ret));
>  		}
> +		pthread_attr_destroy(&attr);
>  		for (i = 0; i < nr_threads; i++)
>  			pthread_join(thread_data[i].thread, NULL);
>  		cleanup_thread();