Re: [PATCH] fix threaded grep for machines with only one cpu

> Junio C Hamano <gitster@pobox.com> writes:
>
>> Is this the answer to my question?
>
> IOW, please try this patch.  I am planning to queue it to 'maint' as part
> of 1.7.0.1 if this is the right solution (which I obviously think it is).
>
> -- >8 --
> From: Junio C Hamano <gitster@pobox.com>
> Date: Mon, 15 Feb 2010 18:34:28 -0800
> Subject: [PATCH] Fix use of mutex in threaded grep
>
> The program can decide at runtime not to use threading even if the
> support is compiled in.  In such a case, mutexes are not necessary
> and left uninitialized.  But the code incorrectly tried to take and
> release the read_sha1_mutex unconditionally.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  builtin-grep.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/builtin-grep.c b/builtin-grep.c
> index 26d4deb..5c1545e 100644
> --- a/builtin-grep.c
> +++ b/builtin-grep.c
> @@ -81,8 +81,8 @@ static pthread_mutex_t read_sha1_mutex;
>
>  #define grep_lock() pthread_mutex_lock(&grep_mutex)
>  #define grep_unlock() pthread_mutex_unlock(&grep_mutex)
> -#define read_sha1_lock() pthread_mutex_lock(&read_sha1_mutex)
> -#define read_sha1_unlock() pthread_mutex_unlock(&read_sha1_mutex)
> +#define read_sha1_lock() do { if (use_threads) pthread_mutex_lock(&read_sha1_mutex); } while (0)
> +#define read_sha1_unlock() do { if (use_threads) pthread_mutex_unlock(&read_sha1_mutex); } while (0)
>
>  /* Signalled when a new work_item is added to todo. */
>  static pthread_cond_t cond_add;