gdbserver: Leave already-vCont-resumed threads as they were
Currently GDB never sends more than one action per vCont packet, when connected in non-stop mode. A follow up patch will change that, and it exposed a gdbserver problem with the vCont handling. For example, this in non-stop mode: => vCont;s:p1.1;c <= OK Should be equivalent to: => vCont;s:p1.1 <= OK => vCont;c <= OK But gdbserver currently doesn't handle this. In the latter case, "vCont;c" makes gdbserver clobber the previous step request. This patch fixes that. Note the server side must ignore resume actions for the thread that has a pending %Stopped notification (and any other threads with events pending), until GDB acks the notification with vStopped. Otherwise, e.g., the following case is mishandled: #1 => g (or any other packet) #2 <= [registers] #3 <= %Stopped T05 thread:p1.2 #4 => vCont s:p1.1;c #5 <= OK Above, the server must not resume thread p1.2 when it processes the vCont. GDB can't know that p1.2 stopped until it acks the %Stopped notification. (Otherwise it wouldn't send a default "c" action.) (The vCont documentation already specifies this.) Finally, special care must also be given to handling fork/vfork events. A (v)fork event actually tells us that two processes stopped -- the parent and the child. Until we follow the fork, we must not resume the child. Therefore, if we have a pending fork follow, we must not send a global wildcard resume action (vCont;c). We can still send process-wide wildcards though. (The comments above will be added as code comments to gdb in a follow up patch.) gdb/gdbserver/ChangeLog: 2016-10-26 Pedro Alves <palves@redhat.com> * linux-low.c (handle_extended_wait): Link parent/child fork threads. (linux_wait_1): Unlink them. (linux_set_resume_request): Ignore resume requests for already-resumed and unhandled fork child threads. * linux-low.h (struct lwp_info) <fork_relative>: New field. * server.c (in_queued_stop_replies_ptid, in_queued_stop_replies): New functions. (handle_v_requests) <vCont>: Don't call require_running. * server.h (in_queued_stop_replies): New declaration.
This commit is contained in:
parent
ca6eff5908
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5a04c4cf5d
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@ -1,3 +1,16 @@
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2016-10-26 Pedro Alves <palves@redhat.com>
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* linux-low.c (handle_extended_wait): Link parent/child fork
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threads.
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(linux_wait_1): Unlink them.
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(linux_set_resume_request): Ignore resume requests for
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already-resumed and unhandled fork child threads.
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* linux-low.h (struct lwp_info) <fork_relative>: New field.
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* server.c (in_queued_stop_replies_ptid, in_queued_stop_replies):
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New functions.
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(handle_v_requests) <vCont>: Don't call require_running.
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* server.h (in_queued_stop_replies): New declaration.
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2016-10-24 Yao Qi <yao.qi@linaro.org>
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2016-10-24 Yao Qi <yao.qi@linaro.org>
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PR server/20733
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PR server/20733
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@ -589,6 +589,11 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
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event_lwp->status_pending_p = 1;
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event_lwp->status_pending_p = 1;
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event_lwp->status_pending = wstat;
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event_lwp->status_pending = wstat;
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/* Link the threads until the parent event is passed on to
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higher layers. */
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event_lwp->fork_relative = child_lwp;
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child_lwp->fork_relative = event_lwp;
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/* If the parent thread is doing step-over with single-step
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/* If the parent thread is doing step-over with single-step
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breakpoints, the list of single-step breakpoints are cloned
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breakpoints, the list of single-step breakpoints are cloned
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from the parent's. Remove them from the child process.
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from the parent's. Remove them from the child process.
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@ -3853,6 +3858,15 @@ linux_wait_1 (ptid_t ptid,
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{
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{
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/* If the reported event is an exit, fork, vfork or exec, let
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/* If the reported event is an exit, fork, vfork or exec, let
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GDB know. */
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GDB know. */
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/* Break the unreported fork relationship chain. */
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if (event_child->waitstatus.kind == TARGET_WAITKIND_FORKED
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|| event_child->waitstatus.kind == TARGET_WAITKIND_VFORKED)
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{
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event_child->fork_relative->fork_relative = NULL;
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event_child->fork_relative = NULL;
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}
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*ourstatus = event_child->waitstatus;
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*ourstatus = event_child->waitstatus;
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/* Clear the event lwp's waitstatus since we handled it already. */
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/* Clear the event lwp's waitstatus since we handled it already. */
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event_child->waitstatus.kind = TARGET_WAITKIND_IGNORE;
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event_child->waitstatus.kind = TARGET_WAITKIND_IGNORE;
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@ -4654,6 +4668,51 @@ linux_set_resume_request (struct inferior_list_entry *entry, void *arg)
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continue;
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continue;
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}
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}
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/* Ignore (wildcard) resume requests for already-resumed
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threads. */
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if (r->resume[ndx].kind != resume_stop
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&& thread->last_resume_kind != resume_stop)
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{
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if (debug_threads)
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debug_printf ("already %s LWP %ld at GDB's request\n",
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(thread->last_resume_kind
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== resume_step)
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? "stepping"
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: "continuing",
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lwpid_of (thread));
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continue;
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}
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/* Don't let wildcard resumes resume fork children that GDB
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does not yet know are new fork children. */
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if (lwp->fork_relative != NULL)
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{
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struct inferior_list_entry *inf, *tmp;
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struct lwp_info *rel = lwp->fork_relative;
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if (rel->status_pending_p
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&& (rel->waitstatus.kind == TARGET_WAITKIND_FORKED
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|| rel->waitstatus.kind == TARGET_WAITKIND_VFORKED))
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{
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if (debug_threads)
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debug_printf ("not resuming LWP %ld: has queued stop reply\n",
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lwpid_of (thread));
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continue;
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}
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}
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/* If the thread has a pending event that has already been
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reported to GDBserver core, but GDB has not pulled the
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event out of the vStopped queue yet, likewise, ignore the
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(wildcard) resume request. */
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if (in_queued_stop_replies (entry->id))
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{
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if (debug_threads)
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debug_printf ("not resuming LWP %ld: has queued stop reply\n",
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lwpid_of (thread));
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continue;
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}
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lwp->resume = &r->resume[ndx];
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lwp->resume = &r->resume[ndx];
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thread->last_resume_kind = lwp->resume->kind;
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thread->last_resume_kind = lwp->resume->kind;
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@ -301,6 +301,12 @@ struct lwp_info
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information or exit status until it can be reported to GDB. */
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information or exit status until it can be reported to GDB. */
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struct target_waitstatus waitstatus;
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struct target_waitstatus waitstatus;
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/* A pointer to the fork child/parent relative. Valid only while
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the parent fork event is not reported to higher layers. Used to
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avoid wildcard vCont actions resuming a fork child before GDB is
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notified about the parent's fork event. */
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struct lwp_info *fork_relative;
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/* When stopped is set, this is where the lwp last stopped, with
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/* When stopped is set, this is where the lwp last stopped, with
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decr_pc_after_break already accounted for. If the LWP is
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decr_pc_after_break already accounted for. If the LWP is
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running, this is the address at which the lwp was resumed. */
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running, this is the address at which the lwp was resumed. */
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@ -193,6 +193,38 @@ vstop_notif_reply (struct notif_event *event, char *own_buf)
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prepare_resume_reply (own_buf, vstop->ptid, &vstop->status);
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prepare_resume_reply (own_buf, vstop->ptid, &vstop->status);
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}
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}
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/* QUEUE_iterate callback helper for in_queued_stop_replies. */
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static int
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in_queued_stop_replies_ptid (QUEUE (notif_event_p) *q,
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QUEUE_ITER (notif_event_p) *iter,
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struct notif_event *event,
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void *data)
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{
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ptid_t filter_ptid = *(ptid_t *) data;
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struct vstop_notif *vstop_event = (struct vstop_notif *) event;
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if (ptid_match (vstop_event->ptid, filter_ptid))
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return 0;
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/* Don't resume fork children that GDB does not know about yet. */
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if ((vstop_event->status.kind == TARGET_WAITKIND_FORKED
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|| vstop_event->status.kind == TARGET_WAITKIND_VFORKED)
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&& ptid_match (vstop_event->status.value.related_pid, filter_ptid))
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return 0;
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return 1;
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}
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/* See server.h. */
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int
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in_queued_stop_replies (ptid_t ptid)
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{
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return !QUEUE_iterate (notif_event_p, notif_stop.queue,
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in_queued_stop_replies_ptid, &ptid);
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}
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struct notif_server notif_stop =
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struct notif_server notif_stop =
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{
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{
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"vStopped", "Stop", NULL, vstop_notif_reply,
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"vStopped", "Stop", NULL, vstop_notif_reply,
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@ -2947,7 +2979,6 @@ handle_v_requests (char *own_buf, int packet_len, int *new_packet_len)
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if (startswith (own_buf, "vCont;"))
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if (startswith (own_buf, "vCont;"))
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{
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{
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require_running (own_buf);
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handle_v_cont (own_buf);
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handle_v_cont (own_buf);
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return;
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return;
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}
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}
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@ -123,6 +123,10 @@ extern int handle_target_event (int err, gdb_client_data client_data);
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/* Get rid of the currently pending stop replies that match PTID. */
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/* Get rid of the currently pending stop replies that match PTID. */
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extern void discard_queued_stop_replies (ptid_t ptid);
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extern void discard_queued_stop_replies (ptid_t ptid);
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/* Returns true if there's a pending stop reply that matches PTID in
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the vStopped notifications queue. */
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extern int in_queued_stop_replies (ptid_t ptid);
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#include "remote-utils.h"
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#include "remote-utils.h"
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#include "utils.h"
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#include "utils.h"
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