[Qemu-devel] [PATCH 1/8] tls: require compiler support for __thread

[Paolo Bonzini]

The block layer is now using __thread unconditionally.  Remove the
"fake" TLS wrappers (that actually aren't TLS on !Linux) in
include/qemu/tls.h, and add a testcase.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 configure          |  9 +-----
 exec.c             |  2 +-
 include/qemu/tls.h | 52 ----------------------------------
 include/qom/cpu.h  |  4 +--
 tests/Makefile     |  7 ++++-
 tests/test-tls.c   | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 92 insertions(+), 65 deletions(-)
 delete mode 100644 include/qemu/tls.h
 create mode 100644 tests/test-tls.c

diff --git a/configure b/configure
index 7539645..0580606 100755
--- a/configure
+++ b/configure
@@ -1554,14 +1554,7 @@ fi
 
 if test "$pie" != "no" ; then
   cat > $TMPC << EOF
-
-#ifdef __linux__
-#  define THREAD __thread
-#else
-#  define THREAD
-#endif
-
-static THREAD int tls_var;
+static __thread int tls_var;
 
 int main(void) { return tls_var; }
 
diff --git a/exec.c b/exec.c
index 081818e..9046203 100644
--- a/exec.c
+++ b/exec.c
@@ -85,7 +85,7 @@ static MemoryRegion io_mem_unassigned;
 struct CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus);
 /* current CPU in the current thread. It is only valid inside
    cpu_exec() */
-DEFINE_TLS(CPUState *, current_cpu);
+__thread CPUState *current_cpu;
 /* 0 = Do not count executed instructions.
    1 = Precise instruction counting.
    2 = Adaptive rate instruction counting.  */
diff --git a/include/qemu/tls.h b/include/qemu/tls.h
deleted file mode 100644
index b92ea9d..0000000
--- a/include/qemu/tls.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
- * Abstraction layer for defining and using TLS variables
- *
- * Copyright (c) 2011 Red Hat, Inc
- * Copyright (c) 2011 Linaro Limited
- *
- * Authors:
- *  Paolo Bonzini <address@hidden>
- *  Peter Maydell <address@hidden>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, see <http://www.gnu.org/licenses/>.
- */
-
-#ifndef QEMU_TLS_H
-#define QEMU_TLS_H
-
-/* Per-thread variables. Note that we only have implementations
- * which are really thread-local on Linux; the dummy implementations
- * define plain global variables.
- *
- * This means that for the moment use should be restricted to
- * per-VCPU variables, which are OK because:
- *  - the only -user mode supporting multiple VCPU threads is linux-user
- *  - TCG system mode is single-threaded regarding VCPUs
- *  - KVM system mode is multi-threaded but limited to Linux
- *
- * TODO: proper implementations via Win32 .tls sections and
- * POSIX pthread_getspecific.
- */
-#ifdef __linux__
-#define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
-#define DEFINE_TLS(type, x)  __thread __typeof__(type) tls__##x
-#define tls_var(x)           tls__##x
-#else
-/* Dummy implementations which define plain global variables */
-#define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
-#define DEFINE_TLS(type, x)  __typeof__(type) tls__##x
-#define tls_var(x)           tls__##x
-#endif
-
-#endif
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 2098f1c..a93466d 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -26,7 +26,6 @@
 #include "exec/hwaddr.h"
 #include "qemu/queue.h"
 #include "qemu/thread.h"
-#include "qemu/tls.h"
 #include "qemu/typedefs.h"
 
 typedef int (*WriteCoreDumpFunction)(const void *buf, size_t size,
@@ -310,8 +309,7 @@ extern struct CPUTailQ cpus;
     QTAILQ_FOREACH_SAFE(cpu, &cpus, node, next_cpu)
 #define first_cpu QTAILQ_FIRST(&cpus)
 
-DECLARE_TLS(CPUState *, current_cpu);
-#define current_cpu tls_var(current_cpu)
+extern __thread CPUState *current_cpu;
 
 /**
  * cpu_paging_enabled:
diff --git a/tests/Makefile b/tests/Makefile
index e4ddb6a..47ba143 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -57,6 +57,9 @@ check-unit-y += tests/test-cutils$(EXESUF)
 gcov-files-test-cutils-y += util/cutils.c
 check-unit-y += tests/test-mul64$(EXESUF)
 gcov-files-test-mul64-y = util/host-utils.c
+check-unit-y += tests/test-tls$(EXESUF)
+# all code tested by test-tls is inside test-tls.c
+gcov-files-test-tls-y =
 check-unit-y += tests/test-int128$(EXESUF)
 # all code tested by test-int128 is inside int128.h
 gcov-files-test-int128-y =
@@ -223,7 +226,7 @@ test-obj-y = tests/check-qint.o tests/check-qstring.o 
tests/check-qdict.o \
        tests/test-qmp-input-visitor.o tests/test-qmp-input-strict.o \
        tests/test-qmp-commands.o tests/test-visitor-serialization.o \
        tests/test-x86-cpuid.o tests/test-mul64.o tests/test-int128.o \
-       tests/test-opts-visitor.o tests/test-qmp-event.o
+       tests/test-opts-visitor.o tests/test-qmp-event.o tests/test-tls.o
 
 test-qapi-obj-y = tests/test-qapi-visit.o tests/test-qapi-types.o \
                  tests/test-qapi-event.o
@@ -252,6 +255,8 @@ tests/test-x86-cpuid$(EXESUF): tests/test-x86-cpuid.o
 tests/test-xbzrle$(EXESUF): tests/test-xbzrle.o migration/xbzrle.o 
page_cache.o libqemuutil.a
 tests/test-cutils$(EXESUF): tests/test-cutils.o util/cutils.o
 tests/test-int128$(EXESUF): tests/test-int128.o
+tests/test-tls$(EXESUF): tests/test-tls.o libqemuutil.a
+
 tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
        hw/core/qdev.o hw/core/qdev-properties.o hw/core/hotplug.o\
        hw/core/irq.o \
diff --git a/tests/test-tls.c b/tests/test-tls.c
new file mode 100644
index 0000000..f798f74
--- /dev/null
+++ b/tests/test-tls.c
@@ -0,0 +1,83 @@
+/*
+ * Unit-tests for compiler-provided TLS
+ *
+ * Copyright (C) 2015 Red Hat Inc.
+ *
+ * Authors:
+ *  Paolo Bonzini <address@hidden>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to 
deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <glib.h>
+#include <errno.h>
+#include <string.h>
+
+#include "qemu-common.h"
+#include "qemu/atomic.h"
+#include "qemu/thread.h"
+
+__thread volatile long long cnt;
+
+#define NUM_THREADS 10
+
+int stop;
+
+static void *test_thread(void *arg)
+{
+    volatile long long **p_ret = arg;
+    long long exp = 0;
+
+    *p_ret = &cnt;
+    g_assert(cnt == 0);
+    while (atomic_mb_read(&stop) == 0) {
+        exp++;
+        cnt++;
+        g_assert(cnt == exp);
+    }
+
+    return NULL;
+}
+
+static void test_tls(void)
+{
+    volatile long long *addr[NUM_THREADS];
+    QemuThread t[NUM_THREADS];
+    int i;
+
+    for (i = 0; i < NUM_THREADS; i++) {
+        qemu_thread_create(&t[i], "test", test_thread, &addr[i], 
QEMU_THREAD_JOINABLE);
+    }
+    g_usleep(1000000);
+    atomic_mb_set(&stop, 1);
+    for (i = 0; i < NUM_THREADS; i++) {
+        qemu_thread_join(&t[i]);
+    }
+    for (i = 1; i < NUM_THREADS; i++) {
+        g_assert(addr[i] != addr[i - 1]);
+    }
+}
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+
+    g_test_add_func("/tls", test_tls);
+    return g_test_run();
+}
-- 
1.8.3.1