[Guile-commits] GNU Guile branch, master, updated. release_1-9-2-101-g71a5964

[Neil Jerram]

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http://git.savannah.gnu.org/cgit/guile.git/commit/?id=71a5964c110bea93ac926331547c25bdff67ce23

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- Log -----------------------------------------------------------------
commit 71a5964c110bea93ac926331547c25bdff67ce23
Author: Ken Raeburn <address@hidden>
Date:   Wed Aug 26 23:30:59 2009 +0100

    Don't leave and reenter guile mode if mutex is available
    
    On Aug 5, 2009, at 10:06, Ken Raeburn wrote:
    > (1) In scm_pthread_mutex_lock, we leave and re-enter guile mode so
    > that we don't block the thread while in guile mode.  But we could
    > use pthread_mutex_trylock first, and avoid the costs scm_leave_guile
    > seems to incur on the Mac.  If we can't acquire the lock, it should
    > return immediately, and then we can do the expensive, blocking
    > version.  A quick, hack version of this changed my run time for
    > A(3,8) from 17.5s to 14.5s, saving about 17%; sigaltstack and
    > sigprocmask are still in the picture, because they're called from
    > scm_catch_with_pre_unwind_handler.  I'll work up a nicer patch
    > later.
    
    Ah, we already had scm_i_pthread_mutex_trylock lying around; that made
    things easy.
    A second timing test with A(3,9) and this version of the patch (based
    on 1.9.1) shows the same improvement.
    
    * libguile/threads.c (scm_pthread_mutex_lock): Try the mutex before
      leaving and reentering guile mode.

-----------------------------------------------------------------------

Summary of changes:
 libguile/threads.c |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/libguile/threads.c b/libguile/threads.c
index 1721e0b..e468f2f 100644
--- a/libguile/threads.c
+++ b/libguile/threads.c
@@ -1826,10 +1826,15 @@ scm_std_select (int nfds,
 int
 scm_pthread_mutex_lock (scm_i_pthread_mutex_t *mutex)
 {
-  scm_t_guile_ticket t = scm_leave_guile ();
-  int res = scm_i_pthread_mutex_lock (mutex);
-  scm_enter_guile (t);
-  return res;
+  if (scm_i_pthread_mutex_trylock (mutex) == 0)
+    return 0;
+  else
+    {
+      scm_t_guile_ticket t = scm_leave_guile ();
+      int res = scm_i_pthread_mutex_lock (mutex);
+      scm_enter_guile (t);
+      return res;
+    }
 }
 
 static void


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