FYI,
I modified the patch slightly.

On 14.10.2016 15:16, Petr Stodulka wrote:
> From: Michael Haggerty <mhag...@alum.mit.edu>
> 
> If there is a broken symlink where a loose reference file is expected,
> then the attempt to open() it fails with ENOENT. This error is
> misinterpreted to mean that the loose reference file itself has
> disappeared due to a race, causing the lookup to be retried. But in
> this scenario, the retries all suffer from the same problem, causing
> an infinite loop.
> 
> So put a limit (of 5) on the number of times that the stat_ref step
> can be retried.
> 
> Based-on-patch-by: Petr Stodulka <pstod...@redhat.com>
> Signed-off-by: Michael Haggerty <mhag...@alum.mit.edu>
> ---
>  refs/files-backend.c | 6 ++++--
>  refs/refs-internal.h | 6 ++++++
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/refs/files-backend.c b/refs/files-backend.c
> index d16feb1..245a0b5 100644
> --- a/refs/files-backend.c
> +++ b/refs/files-backend.c
> @@ -1353,6 +1353,7 @@ static int files_read_raw_ref(struct ref_store 
> *ref_store,
>       int fd;
>       int ret = -1;
>       int save_errno;
> +     int retries = 0;
>  
>       *type = 0;
>       strbuf_reset(&sb_path);
> @@ -1390,7 +1391,8 @@ static int files_read_raw_ref(struct ref_store 
> *ref_store,
>       if (S_ISLNK(st.st_mode)) {
>               strbuf_reset(&sb_contents);
>               if (strbuf_readlink(&sb_contents, path, 0) < 0) {
> -                     if (errno == ENOENT || errno == EINVAL)
> +                     if ((errno == ENOENT || errno == EINVAL) &&
> +                             retries++ < MAXRETRIES) 
>                               /* inconsistent with lstat; retry */
>                               goto stat_ref;
>                       else
> @@ -1426,7 +1428,7 @@ static int files_read_raw_ref(struct ref_store 
> *ref_store,
>        */
>       fd = open(path, O_RDONLY);
>       if (fd < 0) {
> -             if (errno == ENOENT)
> +             if (errno == ENOENT && retries++ < MAXRETRIES)
>                       /* inconsistent with lstat; retry */
>                       goto stat_ref;
>               else
> diff --git a/refs/refs-internal.h b/refs/refs-internal.h
> index 708b260..37e6b99 100644
> --- a/refs/refs-internal.h
> +++ b/refs/refs-internal.h
> @@ -255,6 +255,12 @@ int rename_ref_available(const char *old_refname, const 
> char *new_refname);
>  /* We allow "recursive" symbolic refs. Only within reason, though */
>  #define SYMREF_MAXDEPTH 5
>  
> +/* 
> + * We allow only MAXRETRIES tries to jump on stat_ref, because of possible
> + * infinite loop
> + */
> +#define MAXRETRIES 5
> +
>  /* Include broken references in a do_for_each_ref*() iteration: */
>  #define DO_FOR_EACH_INCLUDE_BROKEN 0x01
>  
> 

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