/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: jan@swi-prolog.org WWW: https://www.swi-prolog.org Copyright (c) 1999-2026, University of Amsterdam VU University Amsterdam SWI-Prolog Solutions b.v. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(thread_util, [ threads/0, % List available threads join_threads/0, % Join all terminated threads with_stopped_threads/2, % :Goal, +Options thread_has_console/0, % True if thread has a console attach_console/0, % Create a new console for thread. attach_console/1, % ?Title tspy/1, % :Spec tspy/2, % :Spec, +ThreadId tdebug/0, tdebug/1, % +ThreadId tnodebug/0, tnodebug/1, % +ThreadId tprofile/1, % +ThreadId tbacktrace/1, % +ThreadId, tbacktrace/2, % +ThreadId, +Options thread_alias/1 % +Alias ]). :- if(current_prolog_flag(xpce, true)). :- export(( interactor/0, interactor/1 % ?Title )). :- autoload(library(epilog), [epilog/1, epilog_attach/1, ep_has_console/1]). :- endif. :- meta_predicate with_stopped_threads(0, +). :- autoload(library(apply), [maplist/3, convlist/3]). :- autoload(library(backcomp), [thread_at_exit/1]). :- autoload(library(edinburgh), [nodebug/0]). :- autoload(library(lists), [max_list/2, append/2]). :- autoload(library(option), [merge_options/3, option/3, option/2]). :- autoload(library(prolog_stack), [print_prolog_backtrace/2, get_prolog_backtrace/3]). :- autoload(library(statistics), [thread_statistics/2]). :- autoload(library(prolog_profile), [show_profile/1]). :- autoload(library(thread), [call_in_thread/2]). :- autoload(library(broadcast), [broadcast/1]). :- autoload(library(prolog_debug), [spy/1]). :- autoload(library(dcg/high_order), [sequence/5]). :- autoload(library(gui_tracer), [guitracer/0, ensure_guitracer/0]). :- set_prolog_flag(generate_debug_info, false). :- module_transparent tspy/1, tspy/2. /** Interactive thread utilities This library provides utilities that are primarily intended for interactive usage in a threaded Prolog environment. It allows for inspecting threads, manage I/O of background threads (depending on the environment) and manipulating the debug status of threads. */ %! threads % % List currently known threads with their status. For each thread it % lists the _id_, _class_, _status_, _debug status_, _CPU time_ and % current _stack usage_. If a thread is listed with _Debug_ set to % `X', it cannot be debugged. If the _Debug_ is show as `V', it is % running in debug mode (see debug/0) and responds to _spy points_ and % _break points_. threads :- threads(Threads), print_message(information, threads(Threads)). threads(Threads) :- findall(Thread, thread_data(Thread), Threads). thread_data(Data) :- thread_statistics(TID, Stats), thread_property(TID, debug(Debug)), ( Debug == true -> thread_property(TID, debug_mode(DebugMode)), put_dict(debug, Stats, DebugMode, Stats1) ; Stats1 = Stats ), ( thread_property(TID, class(Class)) -> put_dict(class, Stats1, Class, Data) ; Data = Stats ). %! join_threads % % Join all terminated threads. For normal applications, dealing with % terminated threads must be part of the application logic, either % detaching the thread before termination or making sure it will be % joined. The predicate join_threads/0 is intended for interactive % sessions to reclaim resources from threads that died unexpectedly % during development. join_threads :- findall(Ripped, rip_thread(Ripped), AllRipped), ( AllRipped == [] -> true ; print_message(informational, joined_threads(AllRipped)) ). rip_thread(thread{id:id, status:Status}) :- thread_property(Id, status(Status)), Status \== running, \+ thread_self(Id), thread_join(Id, _). %! with_stopped_threads(:Goal, Options) is det. % % Stop all threads except the caller while running once(Goal). Note % that this is in the thread user utilities as this is not something % that should be used by normal applications. Notably, this may % _deadlock_ if the current thread requires input from some other % thread to complete Goal or one of the stopped threads has a lock. % Options: % % - stop_nodebug_threads(+Boolean) % If `true` (default `false`), also stop threads created with % the debug(false) option. % - except(+List) % Do not stop threads from this list. % % @bug Note that the threads are stopped when they process signals. As % signal handling may be delayed, this implies they need not be % stopped before Goal starts. :- dynamic stopped_except/1. with_stopped_threads(_, _) :- stopped_except(_), !. with_stopped_threads(Goal, Options) :- thread_self(Me), setup_call_cleanup( asserta(stopped_except(Me), Ref), ( stop_other_threads(Me, Options), once(Goal) ), erase(Ref)). stop_other_threads(Me, Options) :- findall(T, stop_thread(Me, T, Options), Stopped), broadcast(stopped_threads(Stopped)). stop_thread(Me, Thread, Options) :- option(except(Except), Options, []), ( option(stop_nodebug_threads(true), Options) -> thread_property(Thread, status(running)) ; debug_target(Thread) ), Me \== Thread, \+ memberchk(Thread, Except), catch(thread_signal(Thread, stopped_except), error(_,_), fail). stopped_except :- thread_wait(\+ stopped_except(_), [ wait_preds([stopped_except/1]) ]). %! thread_has_console is semidet. % % True when the calling thread has an attached console. % % @see attach_console/0 thread_has_console(main) :- !, \+ current_prolog_flag(epilog, true). thread_has_console(Id) :- thread_property(Id, class(console)), !. :- if(current_predicate(ep_has_console/1)). thread_has_console(Id) :- ep_has_console(Id). :- endif. thread_has_console :- current_prolog_flag(break_level, _), !. thread_has_console :- thread_self(Id), thread_has_console(Id), !. %! attach_console is det. %! attach_console(+Title) is det. % % Create a new console and make the standard Prolog streams point to % it. If not provided, the title is built using the thread id. Does % nothing if the current thread already has a console attached. attach_console :- attach_console(_). attach_console(_) :- thread_has_console, !. :- if(current_predicate(epilog_attach/1)). attach_console(Title) :- thread_self(Me), console_title(Me, Title), epilog_attach([ title(Title) ]). :- endif. attach_console(Title) :- print_message(error, cannot_attach_console(Title)), fail. console_title(Thread, Title) :- current_prolog_flag(system_thread_id, SysId), human_thread_id(Thread, Id), format(atom(Title), 'SWI-Prolog Thread ~w (~d) Interactor', [Id, SysId]). human_thread_id(Thread, Alias) :- thread_property(Thread, alias(Alias)), !. human_thread_id(Thread, Id) :- thread_property(Thread, id(Id)). %! interactor is det. %! interactor(+Title) is det. % % Run a Prolog toplevel in another thread with a new console window. % If Title is given, this will be used as the window title. As of % SWI-Prolog version 10, the console is provided by the XPCE graphics % library using library(epilog). interactor :- interactor(_). :- if(current_predicate(epilog/1)). interactor(Title) :- !, ( nonvar(Title) -> Options = [title(Title)] ; Options = [] ), epilog([ init(true) | Options ]). :- endif. interactor(Title) :- print_message(error, cannot_attach_console(Title)), fail. /******************************* * DEBUGGING * *******************************/ %! tspy(:Spec) is det. %! tspy(:Spec, +ThreadOrClass) is det. % % Trap the graphical debugger on reaching Spec. The predicate tspy/0 % enabled debug mode in all threads using tdebug/0 while tspy/1 % enables debug mode using tdebug/1. tspy(Spec) :- spy(Spec), tdebug. tspy(Spec, ThreadID) :- spy(Spec), tdebug(ThreadID). %! tdebug is det. %! tdebug(+ThreadOrClass) is det. %! tnodebug is det. %! tnodebug(+ThreadOrClass) is det. % % Enable or disable a thread or group of threads for debugging using % the graphical tracer. A group of threads is addressed based on the % `class` property of a thread set by thread_create/3 or set_thread/2. % This implies loading the graphical tracer and switching the thread % to debug mode using debug/0. New threads created inherit their debug % mode from the thread that created them. % % Thread classes have been introduced in SWI-Prolog 10.0.2/10.1.5. % This allows for more selective debugging as well as ensuring % debugging works in newly created threads. For example, the HTTP % server creates all its _worker threads_ in the class `http`. Using % query below, we reliable make sure spy points are trapped in HTTP % handler threads, regardless of whether the worker existed or is % lazily created and regardless of whether the user switched to % _nodebug_ mode while tracing a previous event (see % debug_reset_from_class/0). % % ?- tdebug(http). tdebug :- guitracer, forall(debug_target(Id), set_thread(Id, debug_mode(true))). tdebug(ThreadOrClass) :- ensure_guitracer, tdebug_(ThreadOrClass, true). tdebug_(ThreadID, Mode), is_thread(ThreadID) => set_thread(ThreadID, debug_mode(Mode)). tdebug_(Class, Mode), atom(Class) => '$debug_thread_class'(Class, Mode, Matching, Set), print_message(informational, tdebug(Class, Mode, Matching, Set)). tnodebug :- forall(debug_target(Id), set_thread(Id, set_thread(false))). tnodebug(ThreadOrClass) :- tdebug_(ThreadOrClass, false). debug_target(Thread) :- thread_property(Thread, status(running)), thread_property(Thread, debug(true)). %! tbacktrace(+Thread) is det. %! tbacktrace(+Thread, +Options) is det. % % Print a backtrace for Thread to the stream `user_error` of the % calling thread. This is achieved by inserting an interrupt into % Thread using call_in_thread/2. Options: % % - depth(+MaxFrames) % Number of stack frames to show. Default is the current Prolog % flag `backtrace_depth` or 20. % % Other options are passed to get_prolog_backtrace/3. % % @bug call_in_thread/2 may not process the event. tbacktrace(Thread) :- tbacktrace(Thread, []). tbacktrace(Thread, Options) :- merge_options(Options, [clause_references(false)], Options1), ( current_prolog_flag(backtrace_depth, Default) -> true ; Default = 20 ), option(depth(Depth), Options1, Default), call_in_thread(Thread, thread_get_prolog_backtrace(Depth, Stack, Options1)), print_prolog_backtrace(user_error, Stack). %! thread_get_prolog_backtrace(+Depth, -Stack, +Options) % % As get_prolog_backtrace/3, but starts above the C callback, hiding % the overhead inside call_in_thread/2. thread_get_prolog_backtrace(Depth, Stack, Options) :- prolog_current_frame(Frame), signal_frame(Frame, SigFrame), get_prolog_backtrace(Depth, Stack, [frame(SigFrame)|Options]). signal_frame(Frame, SigFrame) :- prolog_frame_attribute(Frame, clause, _), !, ( prolog_frame_attribute(Frame, parent, Parent) -> signal_frame(Parent, SigFrame) ; SigFrame = Frame ). signal_frame(Frame, SigFrame) :- ( prolog_frame_attribute(Frame, parent, Parent) -> SigFrame = Parent ; SigFrame = Frame ). /******************************* * REMOTE PROFILING * *******************************/ %! tprofile(+Thread) is det. % % Profile the operation of Thread until the user hits a key. tprofile(Thread) :- init_pce, thread_signal(Thread, ( reset_profiler, profiler(_, true) )), format('Running profiler in thread ~w (press RET to show results) ...', [Thread]), flush_output, get_code(_), thread_signal(Thread, ( profiler(_, false), show_profile([]) )). %! init_pce % % Make sure XPCE is running if it is attached, so we can use the % graphical display using in_pce_thread/1. :- if(exists_source(library(pce))). init_pce :- current_prolog_flag(gui, true), !, autoload_call(send(@(display), open)). :- endif. init_pce. /******************************* * COMPATIBILITY * *******************************/ %! thread_alias(+Alias) is det. % % Set the alias for a thread. % % @deprecated Use set_thread/2 using alias(Alias). thread_alias(Alias) :- thread_self(Me), set_thread(Me, alias(Alias)). /******************************* * HOOKS * *******************************/ :- multifile prolog:message_action/2. prolog:message_action(trace_mode(on), _Level) :- \+ thread_has_console, \+ current_prolog_flag(gui_tracer, true), catch(attach_console, error(_,_), fail). :- multifile prolog:message/3. prolog:message(thread_welcome) --> { thread_self(Self), human_thread_id(Self, Id) }, [ 'SWI-Prolog console for thread ~w'-[Id], nl, nl ]. prolog:message(joined_threads(Threads)) --> [ 'Joined the following threads'-[], nl ], thread_list(Threads). prolog:message(threads(Threads)) --> thread_list(Threads). prolog:message(cannot_attach_console(_Title)) --> [ 'Cannot attach a console (requires xpce package)' ]. prolog:message(tdebug(Class, Enable, Matched, Set)) --> ( { var(Matched) } -> [ 'Debug for threads in class '], thread_class(Class), [' was already ' ], enabled(Enable) ; 'Enabled'(Enable), [ ' debug mode in ' ], change_counts(Matched, Set), [' threads in class ' ], thread_class(Class) ). enabled(true) ==> ['enabled']. enabled(false) ==> ['disabled']. 'Enabled'(true) ==> ['Enabled']. 'Enabled'(false) ==> ['Disabled']. thread_class(Class) --> [ ansi(code, '~q', [Class]) ]. change_counts(Set, Set) ==> [ 'all ~D'-[Set] ]. change_counts(Matched, Set) ==> [ '~D out of ~D'-[Set, Matched] ]. thread_list(Threads) --> { maplist(th_id_len, Threads, Lens), convlist(th_class_len, Threads, CLens), max_list(Lens, MaxWidth0), max_list(CLens, MaxWidth1), LeftColWidth is max(6, MaxWidth0), ClassColWidth is max(6, MaxWidth1+2), Threads = [H|_] }, thread_list_header(H, LeftColWidth, ClassColWidth), sequence(thread_info(LeftColWidth, ClassColWidth), [nl], Threads). th_id_len(Thread, IdLen) :- write_length(Thread.id, IdLen, [quoted(true)]). th_class_len(Thread, ClassLen) :- write_length(Thread.get(class,''), ClassLen, [quoted(true)]). thread_list_header(Thread, NW, CW) --> { _{id:_, status:_, time:_, stacks:_} :< Thread, !, HrWidth is NW+CW+6+10+10+13 }, [ '~|~tThread~*+~tClass~*+~tStatus~10+~tDebug~6+~tTime~10+~tStack use~13+'- [NW,CW], nl ], [ '~|~`\u2015t~*+'-[HrWidth], nl ]. thread_list_header(Thread, NW, _CW) --> { _{id:_, status:_} :< Thread, !, HrWidth is NW+7 }, [ '~|~tThread~*+ Status'-[NW], nl ], [ '~|~`-t~*+'-[HrWidth], nl ]. thread_info(NW, CW, Thread) --> { _{id:Id, status:Status, time:Time, stacks:Stacks} :< Thread, Class = Thread.get(class, -), debug_flag(Thread, Flag) }, !, [ '~|~t~q~*+~t~q~*+~t~w~10+ ~t~w~t~6+~t~3f~10+~t~D~13+'- [ Id, NW, Class, CW, Status, Flag, Time.cpu, Stacks.total.usage ] ]. thread_info(NW, _CW, Thread) --> { _{id:Id, status:Status} :< Thread }, !, [ '~|~t~q~*+ ~w'- [ Id, NW, Status ] ]. debug_flag(Thread, Flag) :- get_dict(class, Thread, console), !, Flag = ''. debug_flag(Thread, Flag) :- get_dict(debug, Thread, Debug), !, ( Debug == true -> Flag = '\u2714' % V ; Flag = '' ). debug_flag(_, '\u2718'). % X