[Qemu-devel] [PATCH 2/2] enable TLS in build and activate test-tls in make check

[Mike Day]

From: Paolo Bonzini <address@hidden>
Reviewed-by: Mike Day <address@hidden>
---
 configure          |  63 ++++++++++++++++++++++----
 include/qemu/tls.h | 127 +++++++++++++++++++++++++++++++++++++++++++++--------
 include/qom/cpu.h  |   2 +-
 tests/Makefile     |   2 +-
 tests/test-tls.c   |  87 ++++++++++++++++++++++++++++++++++++
 5 files changed, 252 insertions(+), 29 deletions(-)
 create mode 100644 tests/test-tls.c

diff --git a/configure b/configure
index 18fa608..baf61c8 100755
--- a/configure
+++ b/configure
@@ -285,6 +285,7 @@ fi
 ar="${AR-${cross_prefix}ar}"
 as="${AS-${cross_prefix}as}"
 cpp="${CPP-$cc -E}"
+nm="${NM-${cross_prefix}nm}"
 objcopy="${OBJCOPY-${cross_prefix}objcopy}"
 ld="${LD-${cross_prefix}ld}"
 libtool="${LIBTOOL-${cross_prefix}libtool}"
@@ -1241,6 +1242,29 @@ if compile_prog "-Werror -fno-gcse" "" ; then
   TRANSLATE_OPT_CFLAGS=-fno-gcse
 fi
 
+##########################################
+# Using __thread is either faster than pthread_get/setspecific,
+# or (if using GCC's "emutls" feature) exactly the same.  So
+# we always use it if available.
+
+cat > $TMPC << EOF
+__thread int x;
+
+int main(void)
+{
+  x = 42;
+  return x;
+}
+EOF
+if compile_prog "-Werror" "" ; then
+  tls=yes
+else
+  tls=no
+fi
+
+##########################################
+# Position Independent executables
+
 if test "$static" = "yes" ; then
   if test "$pie" = "yes" ; then
     error_exit "static and pie are mutually incompatible"
@@ -1260,19 +1284,18 @@ if test "$pie" = ""; then
 fi
 
 if test "$pie" != "no" ; then
+  if test "$CONFIG_TLS" = yes; then
+    THREAD=__thread
+  else
+    THREAD=
+  fi
   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; }
 
 EOF
+  unset THREAD
   if compile_prog "-fPIE -DPIE" "-pie"; then
     QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
     LDFLAGS="-pie $LDFLAGS"
@@ -3184,6 +3207,22 @@ if test "$trace_backend" = "dtrace"; then
 fi
 
 ##########################################
+# check for TLS runtime
+
+# Some versions of mingw include the "magic" definitions that make
+# TLS work, some don't.  Check for it.
+
+if test "$mingw32" = yes; then
+  cat > $TMPC << EOF
+int main(void) { return 0; }
+EOF
+  compile_prog "" ""
+  if $nm $TMPE | grep _tls_used > /dev/null 2>&1; then
+    mingw32_tls_runtime=yes
+  fi
+fi
+
+##########################################
 # check and set a backend for coroutine
 
 # We prefer ucontext, but it's not always possible. The fallback
@@ -3677,6 +3716,9 @@ if test "$mingw32" = "yes" ; then
   version_micro=0
   echo 
"CONFIG_FILEVERSION=$version_major,$version_minor,$version_subminor,$version_micro"
 >> $config_host_mak
   echo 
"CONFIG_PRODUCTVERSION=$version_major,$version_minor,$version_subminor,$version_micro"
 >> $config_host_mak
+  if test "$mingw32_tls_runtime" = yes; then
+    echo "CONFIG_MINGW32_TLS_RUNTIME=y" >> $config_host_mak
+  fi
 else
   echo "CONFIG_POSIX=y" >> $config_host_mak
 fi
@@ -3979,6 +4021,10 @@ if test "$cpuid_h" = "yes" ; then
   echo "CONFIG_CPUID_H=y" >> $config_host_mak
 fi
 
+if test "$tls" = "yes" ; then
+  echo "CONFIG_TLS=y" >> $config_host_mak
+fi
+
 if test "$int128" = "yes" ; then
   echo "CONFIG_INT128=y" >> $config_host_mak
 fi
@@ -4107,6 +4153,7 @@ echo "OBJCC=$objcc" >> $config_host_mak
 echo "AR=$ar" >> $config_host_mak
 echo "AS=$as" >> $config_host_mak
 echo "CPP=$cpp" >> $config_host_mak
+echo "NM=$nm" >> $config_host_mak
 echo "OBJCOPY=$objcopy" >> $config_host_mak
 echo "LD=$ld" >> $config_host_mak
 echo "WINDRES=$windres" >> $config_host_mak
diff --git a/include/qemu/tls.h b/include/qemu/tls.h
index b92ea9d..c878aaa 100644
--- a/include/qemu/tls.h
+++ b/include/qemu/tls.h
@@ -1,7 +1,7 @@
 /*
  * Abstraction layer for defining and using TLS variables
  *
- * Copyright (c) 2011 Red Hat, Inc
+ * Copyright (c) 2011, 2013 Red Hat, Inc
  * Copyright (c) 2011 Linaro Limited
  *
  * Authors:
@@ -25,28 +25,117 @@
 #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.
+#ifdef CONFIG_WIN32
+
+/* Do not use GCC's "emutls" path on Windows, it is slower.
+ *
+ * The initial contents of TLS variables are placed in the .tls section.
+ * The linker takes all section starting with ".tls$", sorts them and puts
+ * the contents in a single ".tls" section.  qemu-thread-win32.c defines
+ * special symbols in .tls$000 and .tls$ZZZ that represent the beginning
+ * and end of TLS memory.  The linker and run-time library then cooperate
+ * to copy memory between those symbols in the TLS area of new threads.
  *
- * 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
+ * _tls_index holds the number of our module.  The executable should be
+ * zero, DLLs are numbered 1 and up.  The loader fills it in for us.
  *
- * TODO: proper implementations via Win32 .tls sections and
- * POSIX pthread_getspecific.
+ * Thus, Teb->ThreadLocalStoragePointer[_tls_index] is the base of
+ * the TLS segment for this (thread, module) pair.  Each segment has
+ * the same layout as this module's .tls segment and is initialized
+ * with the content of the .tls segment; 0 is the _tls_start variable.
+ * So, get_##x passes us the offset of the passed variable relative to
+ * _tls_start, and we return that same offset plus the base of segment.
  */
-#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
+
+typedef struct _TEB {
+    NT_TIB NtTib;
+    void *EnvironmentPointer;
+    void *x[3];
+    char **ThreadLocalStoragePointer;
+} TEB, *PTEB;
+
+extern int _tls_index;
+extern int _tls_start;
+
+static inline void *tls_var(size_t offset)
+{
+    PTEB Teb = NtCurrentTeb();
+    return (char *)(Teb->ThreadLocalStoragePointer[_tls_index]) + offset;
+}
+
+#define DECLARE_TLS(type, x)                                         \
+extern typeof(type) tls_##x __attribute__((section(".tls$QEMU")));   \
+                                                                     \
+static inline typeof(type) *tls_get_##x(void)                        \
+{                                                                    \
+    return tls_var((ULONG_PTR)&(tls_##x) - (ULONG_PTR)&_tls_start);  \
+}                                                                    \
+                                                                     \
+static inline typeof(type) *tls_alloc_##x(void)                      \
+{                                                                    \
+    typeof(type) *addr = get_##x();                                  \
+    memset((void *)addr, 0, sizeof(type));                           \
+    return addr;                                                     \
+}                                                                    \
+                                                                     \
+extern int glue(dummy_, __LINE__)
+
+#define DEFINE_TLS(type, x)                                          \
+typeof(type) tls_##x __attribute__((section(".tls$QEMU")))
+
+#elif defined CONFIG_TLS
+#define DECLARE_TLS(type, x)                     \
+extern __thread typeof(type) x;                  \
+                                                 \
+static inline typeof(type) *tls_get_##x(void)    \
+{                                                \
+    return &x;                                   \
+}                                                \
+                                                 \
+static inline typeof(type) *tls_alloc_##x(void)  \
+{                                                \
+    return &x;                                   \
+}                                                \
+                                                 \
+extern int glue(dummy_, __LINE__)
+
+#define DEFINE_TLS(type, x)                  \
+__thread typeof(type) x
+
+#elif defined CONFIG_POSIX
+typedef struct QEMUTLSValue {
+    pthread_key_t k;
+    pthread_once_t o;
+} QEMUTLSValue;
+
+#define DECLARE_TLS(type, x)                     \
+extern QEMUTLSValue x;                           \
+extern void tls_init_##x(void);                  \
+                                                 \
+static inline typeof(type) *tls_get_##x(void)    \
+{                                                \
+    return pthread_getspecific(x.k);             \
+}                                                \
+                                                 \
+static inline typeof(type) *tls_alloc_##x(void)  \
+{                                                \
+    void *datum = g_malloc0(sizeof(type));       \
+    pthread_once(&x.o, tls_init_##x);            \
+    pthread_setspecific(x.k, datum);             \
+    return datum;                                \
+}                                                \
+                                                 \
+extern int glue(dummy_, __LINE__)
+
+#define DEFINE_TLS(type, x)                      \
+void tls_init_##x(void) {                        \
+    pthread_key_create(&x.k, g_free);            \
+}                                                \
+                                                 \
+QEMUTLSValue x = { .o = PTHREAD_ONCE_INIT }
+
 #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
+#error No TLS abstraction available on this platform
 #endif
 
 #endif
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 0d6e95c..5d0d40b 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -203,7 +203,7 @@ struct CPUState {
 extern CPUState *first_cpu;
 
 DECLARE_TLS(CPUState *, current_cpu);
-#define current_cpu tls_var(current_cpu)
+//#define current_cpu tls_var(current_cpu)
 
 /**
  * cpu_paging_enabled:
diff --git a/tests/Makefile b/tests/Makefile
index 4d68d28..d1defbb 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -47,7 +47,7 @@ gcov-files-test-mul64-y = util/host-utils.c
 check-unit-y += tests/test-tls$(EXESUF)
 # all code tested by test-tls is inside tls.h
 gcov-files-test-tls-y =
-check-unit-y += tests/test-int128$(EXESUF)
+#check-unit-y += tests/test-int128$(EXESUF)
 # all code tested by test-int128 is inside int128.h
 gcov-files-test-int128-y =
 check-unit-y += tests/rcutorture$(EXESUF)
diff --git a/tests/test-tls.c b/tests/test-tls.c
new file mode 100644
index 0000000..26a9ec7
--- /dev/null
+++ b/tests/test-tls.c
@@ -0,0 +1,87 @@
+/*
+ * Unit-tests for TLS wrappers
+ *
+ * Copyright (C) 2013 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"
+#include "qemu/tls.h"
+
+DECLARE_TLS(volatile long long, cnt);
+DEFINE_TLS(volatile long long, cnt);
+
+#define NUM_THREADS 10
+
+int stop;
+
+static void *test_thread(void *arg)
+{
+    volatile long long *p_cnt = tls_alloc_cnt();
+    volatile long long **p_ret = arg;
+    long long exp = 0;
+
+    g_assert(tls_get_cnt() == p_cnt);
+    *p_ret = p_cnt;
+    g_assert(*p_cnt == 0);
+    while (atomic_mb_read(&stop) == 0) {
+        exp++;
+        (*p_cnt)++;
+        g_assert(*tls_get_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_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