[Qemu-devel] [PATCH v2 04/13] exec: do not use qemu/tls.h

[Stefan Hajnoczi <stefanha@redhat.com>]

From: Paolo Bonzini <pbonzini@redhat.com>

The next patch will change qemu/tls.h to support more platforms, but at
some performance cost.  Declare current_cpu directly instead of using
the tls.h abstractions.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
Paolo may have further improvements for these patches.  This is my local version.

 exec.c             | 10 ++++++++--
 include/qemu/tls.h | 52 ----------------------------------------------------
 include/qom/cpu.h  | 14 +++++++++++---
 3 files changed, 19 insertions(+), 57 deletions(-)
 delete mode 100644 include/qemu/tls.h

diff --git a/exec.c b/exec.c
index 80ee2ab..b8db730 100644
--- a/exec.c
+++ b/exec.c
@@ -70,9 +70,15 @@ static MemoryRegion io_mem_unassigned;
 #endif
 
 CPUState *first_cpu;
+
 /* current CPU in the current thread. It is only valid inside
-   cpu_exec() */
-DEFINE_TLS(CPUState *, current_cpu);
+ * cpu_exec().  See comment in include/exec/cpu-all.h.  */
+#if defined CONFIG_KVM || (defined CONFIG_USER_ONLY && defined CONFIG_USE_NPTL)
+__thread CPUState *current_cpu;
+#else
+CPUState *current_cpu;
+#endif
+
 /* 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 <pbonzini@redhat.com>
- *  Peter Maydell <peter.maydell@linaro.org>
- *
- * 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 147c256..cb26e1a 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -24,7 +24,6 @@
 #include "hw/qdev-core.h"
 #include "exec/hwaddr.h"
 #include "qemu/thread.h"
-#include "qemu/tls.h"
 #include "qemu/typedefs.h"
 
 typedef int (*WriteCoreDumpFunction)(void *buf, size_t size, void *opaque);
@@ -163,8 +162,17 @@ struct CPUState {
 
 extern CPUState *first_cpu;
 
-DECLARE_TLS(CPUState *, current_cpu);
-#define current_cpu tls_var(current_cpu)
+/* This is thread-local depending on __linux__ 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
+ */
+#if defined CONFIG_KVM || (defined CONFIG_USER_ONLY && defined CONFIG_USE_NPTL)
+extern __thread CPUState *current_cpu;
+#else
+extern CPUState *current_cpu;
+#endif
+
 
 /**
  * cpu_paging_enabled:
-- 
1.8.1.4