Thread suspension: Implement for Linux

src/trusted/service_runtime/nacl_syscall_hook.c

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
  * NaCl service run-time.
  */
 
@@ skipping 144 matching lines @@
 
   /*
    * before switching back to user module, we need to make sure that the
    * user_ret is properly sandboxed.
    */
   user_ret = (nacl_reg_t) NaClSandboxCodeAddr(nap, (uintptr_t) user_ret);
   /*
    * After this NaClAppThreadSetSuspendState() call, we should not
    * claim any mutexes, otherwise we risk deadlock.  Note that if
    * NACLVERBOSITY is set high enough to enable the NaClLog() calls in
-   * NaClSwitchToApp(), these calls could deadlock on Windows.
+   * NaClSwitchToApp(), these calls could deadlock.
    */
   NaClAppThreadSetSuspendState(natp, NACL_APP_THREAD_TRUSTED,
                                NACL_APP_THREAD_UNTRUSTED);
   NaClStackSafetyNowOnUntrustedStack();
 
   NaClSwitchToApp(natp, user_ret);
   /* NOTREACHED */
 
   fprintf(stderr, "NORETURN NaClSwitchToApp returned!?!\n");
   NaClAbort();
 }