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

[Junio C Hamano <gitster@pobox.com>]

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;
-- 
1.7.0.17.g7e5eb