qemu-tls.h

   1 /*
   2  * Abstraction layer for defining and using TLS variables
   3  *
   4  * Copyright (c) 2011 Red Hat, Inc
   5  * Copyright (c) 2011 Linaro Limited
   6  *
   7  * Authors:
   8  *  Paolo Bonzini <pbonzini@redhat.com>
   9  *  Peter Maydell <peter.maydell@linaro.org>
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License as
  13  * published by the Free Software Foundation; either version 2 of
  14  * the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License along
  22  * with this program; if not, see <http://www.gnu.org/licenses/>.
  23  */
  24
  25 #ifndef QEMU_TLS_H
  26 #define QEMU_TLS_H
  27
  28 /* Per-thread variables. Note that we only have implementations
  29  * which are really thread-local on Linux; the dummy implementations
  30  * define plain global variables.
  31  *
  32  * This means that for the moment use should be restricted to
  33  * per-VCPU variables, which are OK because:
  34  *  - the only -user mode supporting multiple VCPU threads is linux-user
  35  *  - TCG system mode is single-threaded regarding VCPUs
  36  *  - KVM system mode is multi-threaded but limited to Linux
  37  *
  38  * TODO: proper implementations via Win32 .tls sections and
  39  * POSIX pthread_getspecific.
  40  */
  41 #ifdef __linux__
  42 #define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
  43 #define DEFINE_TLS(type, x)  __thread __typeof__(type) tls__##x
  44 #define tls_var(x)           tls__##x
  45 #else
  46 /* Dummy implementations which define plain global variables */
  47 #define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
  48 #define DEFINE_TLS(type, x)  __typeof__(type) tls__##x
  49 #define tls_var(x)           tls__##x
  50 #endif
  51
  52 #endif