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| author | George Joseph <george.joseph@fairview5.com> | 2014-04-23 20:13:30 +0000 |
|---|---|---|
| committer | George Joseph <george.joseph@fairview5.com> | 2014-04-23 20:13:30 +0000 |
| commit | 64045f0b57f8524e133373c1d75a36db3fa022cc (patch) | |
| tree | c3bfcd3ad6bc3809025ec7e417e2d2efe2e331f2 /configure.ac | |
| parent | e6c4b9752116ecc71220c03db1493a05c38b051a (diff) | |
This patch adds support for spinlocks in Asterisk.
There are cases in Asterisk where it might be desirable to lock
a short critical code section but not incur the context switch
and yield penalty of a mutex or rwlock. The primary spinlock
implementations execute exclusively in userspace and therefore
don't incur those penalties. Spinlocks are NOT meant to be a
general replacement for mutexes. They should be used only for
protecting short blocks of critical code such as simple compares
and assignments. Operations that may block, hold a lock, or
cause the thread to give up it's timeslice should NEVER be
attempted in a spinlock.
The first use case for spinlocks is in astobj2 - internal_ao2_ref.
Currently the manipulation of the reference counter is done with
an ast_atomic_fetchadd_int which works fine. When weak reference
containers are introduced however, there's an additional comparison
and assignment that'll need to be done while the lock is held.
A mutex would be way too expensive here, hence the spinlock.
Given that lock contention in this situation would be infrequent,
the overhead of the spinlock is only a few more machine instructions
than the current ast_atomic_fetchadd_int call.
ASTERISK-23553 #close
Review: https://reviewboard.asterisk.org/r/3405/
........
Merged revisions 412976 from http://svn.asterisk.org/svn/asterisk/branches/12
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@412977 65c4cc65-6c06-0410-ace0-fbb531ad65f3
Diffstat (limited to 'configure.ac')
| -rw-r--r-- | configure.ac | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/configure.ac b/configure.ac index 67d264701..3c091bc72 100644 --- a/configure.ac +++ b/configure.ac @@ -818,6 +818,22 @@ AC_DEFINE([HAVE_PTHREAD_MUTEX_RECURSIVE_NP], 1, [Define to 1 if your system defi AC_MSG_RESULT(no) ) +AC_MSG_CHECKING(for PTHREAD_MUTEX_ADAPTIVE_NP in pthread.h) +AC_LINK_IFELSE( +[AC_LANG_PROGRAM([#include <pthread.h>], [int a = PTHREAD_MUTEX_ADAPTIVE_NP;])], +AC_MSG_RESULT(yes) +AC_DEFINE([HAVE_PTHREAD_MUTEX_ADAPTIVE_NP], 1, [Define to 1 if your system defines PTHREAD_MUTEX_ADAPTIVE_NP in pthread.h]), +AC_MSG_RESULT(no) +) + +AC_MSG_CHECKING(for pthread_spinlock_t in pthread.h) +AC_LINK_IFELSE( +[AC_LANG_PROGRAM([#include <pthread.h>], [pthread_spinlock_t spin;])], +AC_MSG_RESULT(yes) +AC_DEFINE([HAVE_PTHREAD_SPINLOCK], 1, [Define to 1 if your system has pthread_spinlock_t in pthread.h]), +AC_MSG_RESULT(no) +) + save_LIBS="$LIBS" save_CFLAGS="$CFLAGS" LIBS="$PTHREAD_LIBS $LIBS" |