From: Fredrik Kuivinen <frekui@gmail.com>
To: Nicolas Pitre <nico@fluxnic.net>
Cc: Shawn Pearce <spearce@spearce.org>,
Junio C Hamano <gitster@pobox.com>,
git@vger.kernel.org, Johannes Sixt <j6t@kdbg.org>
Subject: Re: [PATCH v2] Make xmalloc and xrealloc thread-safe
Date: Wed, 7 Apr 2010 16:45:55 +0200 [thread overview]
Message-ID: <20100407144555.GA23911@fredrik-laptop> (raw)
In-Reply-To: <alpine.LFD.2.00.1004070859540.7232@xanadu.home>
On Wed, Apr 07, 2010 at 09:17:04AM -0400, Nicolas Pitre wrote:
> On Wed, 7 Apr 2010, Shawn Pearce wrote:
> > You mentioned avoiding a recursive mutex only because windows
> > emulation doesn't have support for it. But that's exactly what we
> > need here. Shouldn't windows have a recursive mutex object that can
> > just be used inside of the emulation layer when we really need a
> > recursive mutex?
>
> Maybe. That would in fact just mean pushing the double mutex issue into
> the pthread emulation instead of having it outside it. This would
> impact performances for all mutexes although only one instance of them
> currently require a recursive behavior.
As I mentioned in another mail in this thread, our mutex
implementation on WIN32 already is recursive. It is implemented on top
of the CRITICAL_SECTION type, which is recursive. See
http://msdn.microsoft.com/en-us/library/ms682530%28VS.85%29.aspx
We only need something like the following (on top of Nico's previous
patch). Warning: It hasn't even been compile tested on WIN32.
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 65f797f..19e42cf 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1559,7 +1559,7 @@ static pthread_cond_t progress_cond;
*/
static void init_threaded_search(void)
{
- pthread_mutex_init(&read_mutex, NULL);
+ init_recursive_mutex(&read_mutex);
pthread_mutex_init(&cache_mutex, NULL);
pthread_mutex_init(&progress_mutex, NULL);
pthread_cond_init(&progress_cond, NULL);
diff --git a/thread-utils.c b/thread-utils.c
index 4f9c829..3c8d817 100644
--- a/thread-utils.c
+++ b/thread-utils.c
@@ -1,4 +1,5 @@
#include "cache.h"
+#include <pthread.h>
#if defined(hpux) || defined(__hpux) || defined(_hpux)
# include <sys/pstat.h>
@@ -43,3 +44,24 @@ int online_cpus(void)
return 1;
}
+
+int init_recursive_mutex(pthread_mutex_t *m)
+{
+#ifdef _WIN32
+ /* The mutexes in the WIN32 pthreads emulation layer are
+ * recursive, so we don't have to do anything extra here. */
+ return pthread_mutex_init(m, NULL);
+#else
+ pthread_mutexattr_t a;
+ int ret;
+ if (pthread_mutexattr_init(&a))
+ die("pthread_mutexattr_init failed: %s", strerror(errno));
+
+ if (pthread_mutexattr_settype(&a, PTHREAD_MUTEX_RECURSIVE))
+ die("pthread_mutexattr_settype failed: %s", strerror(errno));
+
+ ret = pthread_mutex_init(m, &a);
+ pthread_mutexattr_destroy(&a);
+ return ret;
+#endif
+}
diff --git a/thread-utils.h b/thread-utils.h
index cce4b77..1727a03 100644
--- a/thread-utils.h
+++ b/thread-utils.h
@@ -2,5 +2,6 @@
#define THREAD_COMPAT_H
extern int online_cpus(void);
+extern int init_recursive_mutex(pthread_mutex_t*);
#endif /* THREAD_COMPAT_H */
next prev parent reply other threads:[~2010-04-07 14:46 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20100323161713.3183.57927.stgit@fredrik-laptop>
2010-03-23 17:31 ` [PATCH 1/2] Make xmalloc and xrealloc thread-safe Fredrik Kuivinen
2010-03-23 18:43 ` Shawn O. Pearce
2010-03-23 21:21 ` Fredrik Kuivinen
2010-03-23 23:50 ` Nicolas Pitre
2010-03-24 15:23 ` Fredrik Kuivinen
2010-03-24 17:53 ` Nicolas Pitre
2010-03-24 18:22 ` Shawn Pearce
2010-03-24 18:44 ` Junio C Hamano
2010-03-24 18:54 ` Nicolas Pitre
2010-03-24 19:57 ` Shawn Pearce
2010-03-24 20:22 ` [PATCH] " Nicolas Pitre
2010-03-24 20:28 ` Shawn O. Pearce
2010-03-24 21:02 ` Nicolas Pitre
2010-03-24 21:11 ` Junio C Hamano
2010-03-24 21:28 ` Junio C Hamano
2010-03-27 13:26 ` Fredrik Kuivinen
2010-03-27 18:59 ` Nicolas Pitre
2010-03-31 6:57 ` Fredrik Kuivinen
2010-04-07 2:57 ` [PATCH v2] " Nicolas Pitre
2010-04-07 3:16 ` Shawn O. Pearce
2010-04-07 4:51 ` Nicolas Pitre
2010-04-07 12:29 ` Shawn Pearce
2010-04-07 13:17 ` Nicolas Pitre
2010-04-07 14:30 ` Shawn Pearce
2010-04-07 14:47 ` Nicolas Pitre
2010-04-07 14:45 ` Fredrik Kuivinen [this message]
2010-04-07 15:08 ` Nicolas Pitre
2010-04-07 16:13 ` Fredrik Kuivinen
2010-04-07 16:44 ` Erik Faye-Lund
2010-04-07 18:37 ` Nicolas Pitre
2010-04-07 15:27 ` Sverre Rabbelier
2010-04-07 16:15 ` Fredrik Kuivinen
2010-04-07 16:17 ` Junio C Hamano
2010-04-07 18:49 ` Johannes Sixt
2010-04-08 7:15 ` [PATCH] Thread-safe xmalloc and xrealloc needs a recursive mutex Johannes Sixt
2010-04-08 8:42 ` Fredrik Kuivinen
2010-04-07 5:21 ` [PATCH v2] Make xmalloc and xrealloc thread-safe Junio C Hamano
2010-03-23 17:31 ` [PATCH 2/2] Make sha1_to_hex thread-safe Fredrik Kuivinen
2010-03-23 20:23 ` Johannes Sixt
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