1 /**************************************************************************/ 2 /* */ 3 /* OCaml */ 4 /* */ 5 /* Xavier Leroy and Damien Doligez, INRIA Rocquencourt */ 6 /* */ 7 /* Copyright 1995 Institut National de Recherche en Informatique et */ 8 /* en Automatique. */ 9 /* */ 10 /* All rights reserved. This file is distributed under the terms of */ 11 /* the GNU Lesser General Public License version 2.1, with the */ 12 /* special exception on linking described in the file LICENSE. */ 13 /* */ 14 /**************************************************************************/ 15 16 #ifndef CAML_THREADS_H 17 #define CAML_THREADS_H 18 19 #ifdef __cplusplus 20 extern "C" { 21 #endif 22 23 CAMLextern void caml_enter_blocking_section (void); 24 CAMLextern void caml_leave_blocking_section (void); 25 #define caml_acquire_runtime_system caml_leave_blocking_section 26 #define caml_release_runtime_system caml_enter_blocking_section 27 28 /* Manage the master lock around the OCaml run-time system. 29 Only one thread at a time can execute OCaml compiled code or 30 OCaml run-time system functions. 31 32 When OCaml calls a C function, the current thread holds the master 33 lock. The C function can release it by calling 34 [caml_release_runtime_system]. Then, another thread can execute OCaml 35 code. However, the calling thread must not access any OCaml data, 36 nor call any runtime system function, nor call back into OCaml. 37 38 Before returning to its OCaml caller, or accessing OCaml data, 39 or call runtime system functions, the current thread must 40 re-acquire the master lock by calling [caml_acquire_runtime_system]. 41 42 Symmetrically, if a C function (not called from OCaml) wishes to 43 call back into OCaml code, it should invoke [caml_acquire_runtime_system] 44 first, then do the callback, then invoke [caml_release_runtime_system]. 45 46 For historical reasons, alternate names can be used: 47 [caml_enter_blocking_section] instead of [caml_release_runtime_system] 48 [caml_leave_blocking_section] instead of [caml_acquire_runtime_system] 49 Intuition: a ``blocking section'' is a piece of C code that does not 50 use the runtime system (typically, a blocking I/O operation). 51 */ 52 53 CAMLextern int caml_c_thread_register(void); 54 CAMLextern int caml_c_thread_unregister(void); 55 56 /* If a thread is created by C code (instead of by OCaml itself), 57 it must be registered with the OCaml runtime system before 58 being able to call back into OCaml code or use other runtime system 59 functions. Just call [caml_c_thread_register] once. 60 Before the thread finishes, it must call [caml_c_thread_unregister]. 61 Both functions return 1 on success, 0 on error. 62 */ 63 64 #ifdef __cplusplus 65 } 66 #endif 67 68 #endif /* CAML_THREADS_H */ 69