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authorPedro Alves <palves@redhat.com>2015-08-25 16:12:11 +0100
committerPedro Alves <palves@redhat.com>2015-08-25 16:12:11 +0100
commitabc56d60aacccb64e146eb7a245b3ca2cea52dd9 (patch)
tree6a0ea09e23408052a560920d7c0aac101ed7cfa0 /gdb/target.h
parent38074311927d012e4cbd28d825878974c9209f77 (diff)
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remote: allow aborting long operations (e.g., file transfers)
Currently, when remote debugging, if you type Ctrl-C just while the target stopped for an internal event, and GDB is busy doing something that takes a while (e.g., fetching chunks of a shared library off of the target, with vFile, to process ELF headers and debug info), the Ctrl-C is lost. The patch hooks up the QUIT macro to a new target method that lets the target react to the double-Ctrl-C before the event loop is reached, which allows reacting to a double-Ctrl-C even when GDB is busy doing some long operation and not waiting for a stop reply. That end result is: (gdb) c Continuing. ^C ^C Interrupted while waiting for the program. Give up waiting? (y or n) y Quit (gdb) info threads Id Target Id Frame * 1 Thread 11673 0x00007ffff7deb240 in _dl_debug_state () from target:/lib64/ld-linux-x86-64.so.2 (gdb) If, however, GDB is waiting for a stop reply (because the target has been resumed, with e.g., vCont;c), but the target isn't responding, we now get: (gdb) c Continuing. ^C ^C The target is not responding to interrupt requests. Stop debugging it? (y or n) y Disconnected from target. (gdb) info threads No threads. This offers to disconnect, because when we're waiting for a stop reply, there's nothing else we can send the target other than an interrupt request. And if that doesn't work, there's nothing else we can do. The Ctrl-C is presently lost because until we get to a user-visible stop, the SIGINT handler that is installed is the one that forwards the interrupt to the remote side, with the \003 "packet" [1]. But, gdbserver ignores an interrupt request if the program is stopped. Still, even if it didn't, the server can only report back a stop-because-of-SIGINT when the program is next resumed. And it may take a while to actually re-resume the target. [1] - In the old sync days, the remote target would react to a double-Ctrl-C by asking users whether they wanted to give up waiting and disconnect. The code is still there, but it it isn't reacheable on most hosts, which support serial connections in async mode (probably only DJGPP doesn't). Even then, in sync mode, remote.c's SIGINT handler is only installed while the target is resumed, and is removed as soon as the target sends back a stop reply. That means that a Ctrl-C just while GDB is processing an internal event can end up with an odd "Quit" at the prompt instead of "Program stopped by SIGINT". In contrast, in async mode, remote.c's SIGINT handler is set up as long as target_terminal_inferior or target_terminal_ours_for_output are in effect (IOW, until we get a user-visible stop and call target_terminal_ours), so the user shouldn't get back a spurious Quit. However, it's still desirable to be able to interrupt a long-running GDB operation, if GDB takes a while to re-resume the target or get back to the event loop. Tested on x86_64 Fedora 20. gdb/ChangeLog: 2015-08-24 Pedro Alves <palves@redhat.com> * defs.h (maybe_quit): Declare. (QUIT): Now calls maybe_quit. * event-loop.c (clear_async_signal_handler) (async_signal_handler_is_marked): New functions. * event-loop.h (async_signal_handler_is_marked) (clear_async_signal_handler): New declarations. * remote.c (remote_check_pending_interrupt): New function. (interrupt_query): Use make_cleanup_restore_target_terminal. No longer check whether the target is async. If waiting for a stop reply, and a Ctrl-C as been sent to the target, offer to disconnect, and throw TARGET_CLOSE_ERROR instead of a quit. Otherwise do not disconnect and throw a quit. (_initialize_remote): Install remote_check_pending_interrupt as to_check_pending_interrupt. * target.c (target_check_pending_interrupt): New function. * target.h (struct target_ops) <to_check_pending_interrupt>: New field. (target_check_pending_interrupt): New declaration. * utils.c (maybe_quit): New function. * target-delegates.c: Regenerate.
Diffstat (limited to 'gdb/target.h')
-rw-r--r--gdb/target.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/gdb/target.h b/gdb/target.h
index 1fdaf00..37e4edb 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -642,6 +642,8 @@ struct target_ops
TARGET_DEFAULT_IGNORE ();
void (*to_interrupt) (struct target_ops *, ptid_t)
TARGET_DEFAULT_IGNORE ();
+ void (*to_check_pending_interrupt) (struct target_ops *)
+ TARGET_DEFAULT_IGNORE ();
void (*to_rcmd) (struct target_ops *,
const char *command, struct ui_file *output)
TARGET_DEFAULT_FUNC (default_rcmd);
@@ -1684,6 +1686,14 @@ extern void target_stop (ptid_t ptid);
extern void target_interrupt (ptid_t ptid);
+/* Some targets install their own SIGINT handler while the target is
+ running. This method is called from the QUIT macro to give such
+ targets a chance to process a Ctrl-C. The target may e.g., choose
+ to interrupt the (potentially) long running operation, or give up
+ waiting and disconnect. */
+
+extern void target_check_pending_interrupt (void);
+
/* Send the specified COMMAND to the target's monitor
(shell,interpreter) for execution. The result of the query is
placed in OUTBUF. */