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70b662892c
Even with the previous patch installed, we'll still see sigall-reverse.exp occasionally fail. The problem is that the event loop's event handling processing is done in two steps: #1 - poll all event sources, and push new event objects to the event queue, until all event sources are drained. #2 - go through the event queue, processing each event object at a time. For each event, call the associated callback, and deletes the event object from the queue. and then bad things happen if between #1 and #2 something decides that events from an event source that has already queued events shouldn't be processed yet. To do that, we either remove the event source from the list of event sources, or clear its "have events" flag. However, if an event for that source has meanwhile already been pushed in the event queue, #2 will still process it and call the associated callback... One way to fix it that I considered was to do something to the event objects already in the event queue when an event source is no longer interesting. But then I couldn't find any good reason for the two-step process in the first place. It's much simpler (and less code) to call the event source callbacks as we poll the sources and find events. Tested on x86-64 Fedora 20, native and gdbserver. gdb/ 2015-02-03 Pedro Alves <palves@redhat.com> * event-loop.c: Don't declare nor define a queue type for gdb_event_p. (event_queue): Delete. (create_event, create_file_event, gdb_event_xfree) (initialize_event_loop, process_event): Delete. (gdb_do_one_event): Return as soon as one event is handled. (handle_file_event): Change prototype. Used the passed in file_handler pointer and ready_mask instead of looping over all file handlers. (gdb_wait_for_event): Update the poll/select timeouts before blocking. Run event handlers directly instead of queueing events. Return as soon as one event is handled. (struct async_event_handler_data): Delete. (invoke_async_event_handler): Delete. (check_async_event_handlers): Change return type to int. Run event handlers directly instead of queueing events. Return as soon as one event is handled. (handle_timer_event): Delete. (update_wait_timeout): New function, factored out from poll_timers. (poll_timers): Reimplement. * event-loop.h (initialize_event_loop): Delete declaration. * top.c (gdb_init): Don't call initialize_event_loop.
137 lines
6.4 KiB
C
137 lines
6.4 KiB
C
/* Definitions used by the GDB event loop.
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Copyright (C) 1999-2015 Free Software Foundation, Inc.
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Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* An event loop listens for events from multiple event sources. When
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an event arrives, it is queued and processed by calling the
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appropriate event handler. The event loop then continues to listen
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for more events. An event loop completes when there are no event
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sources to listen on. External event sources can be plugged into
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the loop.
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There are 4 main components:
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- a list of file descriptors to be monitored, GDB_NOTIFIER.
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- a list of asynchronous event sources to be monitored,
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ASYNC_EVENT_HANDLER_LIST.
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- a list of events that have occurred, EVENT_QUEUE.
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- a list of signal handling functions, SIGHANDLER_LIST.
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GDB_NOTIFIER keeps track of the file descriptor based event
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sources. ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous
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event sources that are signalled by some component of gdb, usually
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a target_ops instance. Event sources for gdb are currently the UI
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and the target. Gdb communicates with the command line user
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interface via the readline library and usually communicates with
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remote targets via a serial port. Serial ports are represented in
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GDB as file descriptors and select/poll calls. For native targets
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instead, the communication varies across operating system debug
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APIs, but usually consists of calls to ptrace and waits (via
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signals) or calls to poll/select (via file descriptors). In the
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current gdb, the code handling events related to the target resides
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in wait_for_inferior for synchronous targets; or, for asynchronous
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capable targets, by having the target register either a target
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controlled file descriptor and/or an asynchronous event source in
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the event loop, with the fetch_inferior_event function as the event
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callback. In both the synchronous and asynchronous cases, usually
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the target event is collected through the target_wait interface.
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The target is free to install other event sources in the event loop
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if it so requires.
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EVENT_QUEUE keeps track of the events that have happened during the
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last iteration of the event loop, and need to be processed. An
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event is represented by a procedure to be invoked in order to
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process the event. The queue is scanned head to tail. If the
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event of interest is a change of state in a file descriptor, then a
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call to poll or select will be made to detect it.
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If the events generate signals, they are also queued by special
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functions that are invoked through traditional signal handlers.
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The actions to be taken is response to such events will be executed
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when the SIGHANDLER_LIST is scanned, the next time through the
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infinite loop.
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Corollary tasks are the creation and deletion of event sources. */
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typedef void *gdb_client_data;
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struct async_signal_handler;
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struct async_event_handler;
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typedef void (handler_func) (int, gdb_client_data);
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typedef void (sig_handler_func) (gdb_client_data);
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typedef void (async_event_handler_func) (gdb_client_data);
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typedef void (timer_handler_func) (gdb_client_data);
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/* Exported functions from event-loop.c */
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extern void start_event_loop (void);
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extern int gdb_do_one_event (void);
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extern void delete_file_handler (int fd);
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extern void add_file_handler (int fd, handler_func *proc,
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gdb_client_data client_data);
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extern struct async_signal_handler *
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create_async_signal_handler (sig_handler_func *proc,
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gdb_client_data client_data);
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extern void delete_async_signal_handler (struct async_signal_handler **);
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extern int create_timer (int milliseconds,
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timer_handler_func *proc,
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gdb_client_data client_data);
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extern void delete_timer (int id);
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/* Call the handler from HANDLER immediately. This function
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runs signal handlers when returning to the event loop would be too
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slow. Do not call this directly; use gdb_call_async_signal_handler,
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below, with IMMEDIATE_P == 1. */
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void call_async_signal_handler (struct async_signal_handler *handler);
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/* Call the handler from HANDLER the next time through the event loop.
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Do not call this directly; use gdb_call_async_signal_handler,
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below, with IMMEDIATE_P == 0. */
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void mark_async_signal_handler (struct async_signal_handler *handler);
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/* Wrapper for the body of signal handlers. Call this function from
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any SIGINT handler which needs to access GDB data structures or
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escape via longjmp. If IMMEDIATE_P is set, this triggers either
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immediately (for POSIX platforms), or from gdb_select (for
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MinGW). If IMMEDIATE_P is clear, the handler will run the next
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time we return to the event loop and any current select calls
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will be interrupted. */
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void gdb_call_async_signal_handler (struct async_signal_handler *handler,
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int immediate_p);
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/* Create and register an asynchronous event source in the event loop,
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and set PROC as its callback. CLIENT_DATA is passed as argument to
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PROC upon its invocation. Returns a pointer to an opaque structure
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used to mark as ready and to later delete this event source from
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the event loop. */
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extern struct async_event_handler *
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create_async_event_handler (async_event_handler_func *proc,
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gdb_client_data client_data);
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/* Remove the event source pointed by HANDLER_PTR created by
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CREATE_ASYNC_EVENT_HANDLER from the event loop, and release it. */
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extern void
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delete_async_event_handler (struct async_event_handler **handler_ptr);
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/* Call the handler from HANDLER the next time through the event
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loop. */
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extern void mark_async_event_handler (struct async_event_handler *handler);
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/* Mark the handler (ASYNC_HANDLER_PTR) as NOT ready. */
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extern void clear_async_event_handler (struct async_event_handler *handler);
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