From patchwork Tue Dec  1 12:51:36 2009
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Subject: [v2,10/11] Use __thread where available.
Date: Tue, 01 Dec 2009 02:51:36 -0000
From: Glauber Costa <glommer@redhat.com>
X-Patchwork-Id: 39908
Message-Id: <1259671897-22232-11-git-send-email-glommer@redhat.com>
To: qemu-devel@nongnu.org
Cc: aliguori@us.ibm.com, avi@redhat.com, agraf@suse.de

It is much faster than pthread_{g,s}et_specific.

Signed-off-by: Glauber Costa <glommer@redhat.com>

---
configure |   17 +++++++++++++++++
 vl.c      |   16 ++++++++++++++++
 2 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/configure b/configure
index dca5a43..ce7bcc4 100755
--- a/configure
+++ b/configure
@@ -233,6 +233,7 @@ blobs="yes"
 pkgversion=""
 check_utests="no"
 user_pie="no"
+tls_thread="yes"
 
 # OS specific
 if check_define __linux__ ; then
@@ -1017,6 +1018,19 @@ EOF
 fi
 
 ##########################################
+# Check for availability of the __thread keyword
+cat > $TMPC <<EOF
+__thread void *ptr;
+int main(void) { return 0;}
+EOF
+
+if compile_prog; then
+    tls_thread="yes"
+else
+    tls_thread="no"
+fi
+
+##########################################
 # VNC TLS detection
 if test "$vnc_tls" != "no" ; then
   cat > $TMPC <<EOF
@@ -1969,6 +1983,9 @@ echo "CONFIG_BDRV_WHITELIST=$block_drv_whitelist" >> $config_host_mak
 if test "$mixemu" = "yes" ; then
   echo "CONFIG_MIXEMU=y" >> $config_host_mak
 fi
+if test "$tls_thread" = "yes" ; then
+  echo "CONFIG_TLS_HAS_THREAD=y" >> $config_host_mak
+fi
 if test "$vnc_tls" = "yes" ; then
   echo "CONFIG_VNC_TLS=y" >> $config_host_mak
   echo "VNC_TLS_CFLAGS=$vnc_tls_cflags" >> $config_host_mak
diff --git a/vl.c b/vl.c
index ad2e7d6..16a41e3 100644
--- a/vl.c
+++ b/vl.c
@@ -3445,21 +3445,37 @@ static void block_io_signals(void);
 static void unblock_io_signals(void);
 static int tcg_has_work(void);
 
+#ifdef CONFIG_TLS_HAS_THREAD
+static __thread CPUState *current_env;
+#else
 static pthread_key_t current_env;
+#endif
 
 static CPUState *qemu_get_current_env(void)
 {
+#ifdef CONFIG_TLS_HAS_THREAD
+    return current_env;
+#else
     return pthread_getspecific(current_env);
+#endif
 }
 
 static void qemu_set_current_env(CPUState *env)
 {
+#ifdef CONFIG_TLS_HAS_THREAD
+    current_env = env;
+#else
     pthread_setspecific(current_env, env);
+#endif
 }
 
 static void qemu_init_current_env(void)
 {
+#ifdef CONFIG_TLS_HAS_THREAD
+    current_env = NULL;
+#else
     pthread_key_create(&current_env, NULL);
+#endif
 }
 
 static int qemu_init_main_loop(void)