Re: [PATCH] tmp-objdir: do not opendir() when handling a signal

From: Phillip Wood <phillip.wood123@gmail.com>
Date: Sep 27, 2022, 09:18 UTC
Message-ID: <99c45b89-364f-4f77-7c1b-26231cc7455e@dunelm.org.uk>
In-Reply-To: <pull.1348.git.git.1664236383785.gitgitgadget@gmail.com>

Hi John

On 27/09/2022 00:53, John Cai via GitGitGadget wrote:

Show 10 quoted lines

> From: John Cai <johncai86@gmail.com>
> 
> In the tmp-objdir api, tmp_objdir_create will create a temporary
> directory but also register signal handlers responsible for removing
> the directory's contents and the directory itself. However, the
> function responsible for recursively removing the contents and
> directory, remove_dir_recurse() calls opendir(3) and closedir(3).
> This can be problematic because these functions allocate and free
> memory, which are not async-signal-safe functions. This can lead to
> deadlocks.

Show 8 quoted lines

> --- a/dir.h
> +++ b/dir.h
> @@ -498,6 +498,9 @@ int get_sparse_checkout_patterns(struct pattern_list *pl);
>   /* Remove the_original_cwd too */
>   #define REMOVE_DIR_PURGE_ORIGINAL_CWD 0x08
>   
> +/* Indicates a signal is being handled */
> +#define REMOVE_DIR_SIGNAL 0x16

This is setting the bits for REMOVE_DIR_KEEP_NESTED_GIT and REMOVE_DIR_KEEP_TOPLEVEL is that intentional? (it looks like you've doubled 8 to 16 to get the next free bit but used a hex constant, the earlier constants use decimal)

Best Wishes

Phillip