Waiting for events in async mode
================================
-In async mode, GDB should always be ready to handle both user input and target
-events, so neither blocking waitpid nor sigsuspend are viable
-options. Instead, we should notify the GDB main event loop whenever there's
-unprocessed event from the target. The only way to notify this event loop is
-to make it wait on input from a pipe, and write something to the pipe whenever
-there's event. Obviously, if we fail to notify the event loop if there's
-target event, it's bad. If we notify the event loop when there's no event
-from target, linux-nat.c will detect that there's no event, actually, and
-report event of type TARGET_WAITKIND_IGNORE, but it will waste time and
-better avoided.
-
-The main design point is that every time GDB is outside linux-nat.c, we have a
-SIGCHLD handler installed that is called when something happens to the target
-and notifies the GDB event loop. Also, the event is extracted from the target
-using waitpid and stored for future use. Whenever GDB core decides to handle
-the event, and calls into linux-nat.c, we disable SIGCHLD and process things
-as in sync mode, except that before waitpid call we check if there are any
-previously read events.
-
-It could happen that during event processing, we'll try to get more events
-than there are events in the local queue, which will result to waitpid call.
-Those waitpid calls, while blocking, are guarantied to always have
-something for waitpid to return. E.g., stopping a thread with SIGSTOP, and
-waiting for the lwp to stop.
-
-The event loop is notified about new events using a pipe. SIGCHLD handler does
-waitpid and writes the results in to a pipe. GDB event loop has the other end
-of the pipe among the sources. When event loop starts to process the event
-and calls a function in linux-nat.c, all events from the pipe are transferred
-into a local queue and SIGCHLD is blocked. Further processing goes as in sync
-mode. Before we return from linux_nat_wait, we transfer all unprocessed events
-from local queue back to the pipe, so that when we get back to event loop,
-event loop will notice there's something more to do.
-
-SIGCHLD is blocked when we're inside target_wait, so that should we actually
-want to wait for some more events, SIGCHLD handler does not steal them from
-us. Technically, it would be possible to add new events to the local queue but
-it's about the same amount of work as blocking SIGCHLD.
-
-This moving of events from pipe into local queue and back into pipe when we
-enter/leave linux-nat.c is somewhat ugly. Unfortunately, GDB event loop is
-home-grown and incapable to wait on any queue.
+In async mode, GDB should always be ready to handle both user input
+and target events, so neither blocking waitpid nor sigsuspend are
+viable options. Instead, we should asynchronously notify the GDB main
+event loop whenever there's an unprocessed event from the target. We
+detect asynchronous target events by handling SIGCHLD signals. To
+notify the event loop about target events, the self-pipe trick is used
+--- a pipe is registered as waitable event source in the event loop,
+the event loop select/poll's on the read end of this pipe (as well on
+other event sources, e.g., stdin), and the SIGCHLD handler writes a
+byte to this pipe. This is more portable than relying on
+pselect/ppoll, since on kernels that lack those syscalls, libc
+emulates them with select/poll+sigprocmask, and that is racy
+(a.k.a. plain broken).
+
+Obviously, if we fail to notify the event loop if there's a target
+event, it's bad. OTOH, if we notify the event loop when there's no
+event from the target, linux_nat_wait will detect that there's no real
+event to report, and return event of type TARGET_WAITKIND_IGNORE.
+This is mostly harmless, but it will waste time and is better avoided.
+
+The main design point is that every time GDB is outside linux-nat.c,
+we have a SIGCHLD handler installed that is called when something
+happens to the target and notifies the GDB event loop. Whenever GDB
+core decides to handle the event, and calls into linux-nat.c, we
+process things as in sync mode, except that the we never block in
+sigsuspend.
+
+While processing an event, we may end up momentarily blocked in
+waitpid calls. Those waitpid calls, while blocking, are guarantied to
+return quickly. E.g., in all-stop mode, before reporting to the core
+that an LWP hit a breakpoint, all LWPs are stopped by sending them
+SIGSTOP, and synchronously waiting for the SIGSTOP to be reported.
+Note that this is different from blocking indefinitely waiting for the
+next event --- here, we're already handling an event.
Use of signals
==============
event loop. */
static int linux_nat_event_pipe[2] = { -1, -1 };
-/* Number of queued events in the pipe. */
-static volatile int linux_nat_num_queued_events;
+/* Flush the event pipe. */
-/* The possible SIGCHLD handling states. */
-
-enum sigchld_state
-{
- /* SIGCHLD disabled, with action set to sigchld_handler, for the
- sigsuspend in linux_nat_wait. */
- sigchld_sync,
- /* SIGCHLD enabled, with action set to async_sigchld_handler. */
- sigchld_async,
- /* Set SIGCHLD to default action. Used while creating an
- inferior. */
- sigchld_default
-};
-
-/* The current SIGCHLD handling state. */
-static enum sigchld_state linux_nat_async_events_state;
-
-static enum sigchld_state linux_nat_async_events (enum sigchld_state enable);
-static void pipe_to_local_event_queue (void);
-static void local_event_queue_to_pipe (void);
-static void linux_nat_event_pipe_push (int pid, int status, int options);
-static int linux_nat_event_pipe_pop (int* ptr_status, int* ptr_options);
-static void linux_nat_set_async_mode (int on);
-static void linux_nat_async (void (*callback)
- (enum inferior_event_type event_type, void *context),
- void *context);
-static int linux_nat_async_mask (int mask);
-static int kill_lwp (int lwpid, int signo);
-
-static int stop_callback (struct lwp_info *lp, void *data);
-
-/* Captures the result of a successful waitpid call, along with the
- options used in that call. */
-struct waitpid_result
-{
- int pid;
- int status;
- int options;
- struct waitpid_result *next;
-};
-
-/* A singly-linked list of the results of the waitpid calls performed
- in the async SIGCHLD handler. */
-static struct waitpid_result *waitpid_queue = NULL;
-
-/* Similarly to `waitpid', but check the local event queue instead of
- querying the kernel queue. If PEEK, don't remove the event found
- from the queue. */
-
-static int
-queued_waitpid_1 (int pid, int *status, int flags, int peek)
+static void
+async_file_flush (void)
{
- struct waitpid_result *msg = waitpid_queue, *prev = NULL;
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog,
- "\
-QWPID: linux_nat_async_events_state(%d), linux_nat_num_queued_events(%d)\n",
- linux_nat_async_events_state,
- linux_nat_num_queued_events);
+ int ret;
+ char buf;
- if (flags & __WALL)
- {
- for (; msg; prev = msg, msg = msg->next)
- if (pid == -1 || pid == msg->pid)
- break;
- }
- else if (flags & __WCLONE)
- {
- for (; msg; prev = msg, msg = msg->next)
- if (msg->options & __WCLONE
- && (pid == -1 || pid == msg->pid))
- break;
- }
- else
+ do
{
- for (; msg; prev = msg, msg = msg->next)
- if ((msg->options & __WCLONE) == 0
- && (pid == -1 || pid == msg->pid))
- break;
+ ret = read (linux_nat_event_pipe[0], &buf, 1);
}
-
- if (msg)
- {
- int pid;
-
- if (status)
- *status = msg->status;
- pid = msg->pid;
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog, "QWPID: pid(%d), status(%x)\n",
- pid, msg->status);
-
- if (!peek)
- {
- if (prev)
- prev->next = msg->next;
- else
- waitpid_queue = msg->next;
-
- msg->next = NULL;
- xfree (msg);
- }
-
- return pid;
- }
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog, "QWPID: miss\n");
-
- if (status)
- *status = 0;
- return -1;
+ while (ret >= 0 || (ret == -1 && errno == EINTR));
}
-/* Similarly to `waitpid', but check the local event queue. */
-
-static int
-queued_waitpid (int pid, int *status, int flags)
-{
- return queued_waitpid_1 (pid, status, flags, 0);
-}
+/* Put something (anything, doesn't matter what, or how much) in event
+ pipe, so that the select/poll in the event-loop realizes we have
+ something to process. */
static void
-push_waitpid (int pid, int status, int options)
+async_file_mark (void)
{
- struct waitpid_result *event, *new_event;
+ int ret;
- new_event = xmalloc (sizeof (*new_event));
- new_event->pid = pid;
- new_event->status = status;
- new_event->options = options;
- new_event->next = NULL;
+ /* It doesn't really matter what the pipe contains, as long we end
+ up with something in it. Might as well flush the previous
+ left-overs. */
+ async_file_flush ();
- if (waitpid_queue)
+ do
{
- for (event = waitpid_queue;
- event && event->next;
- event = event->next)
- ;
-
- event->next = new_event;
+ ret = write (linux_nat_event_pipe[1], "+", 1);
}
- else
- waitpid_queue = new_event;
-}
+ while (ret == -1 && errno == EINTR);
-/* Drain all queued events of PID. If PID is -1, the effect is of
- draining all events. */
-static void
-drain_queued_events (int pid)
-{
- while (queued_waitpid (pid, NULL, __WALL) != -1)
- ;
+ /* Ignore EAGAIN. If the pipe is full, the event loop will already
+ be awakened anyway. */
}
+static void linux_nat_async (void (*callback)
+ (enum inferior_event_type event_type, void *context),
+ void *context);
+static int linux_nat_async_mask (int mask);
+static int kill_lwp (int lwpid, int signo);
+
+static int stop_callback (struct lwp_info *lp, void *data);
+
+static void block_child_signals (sigset_t *prev_mask);
+static void restore_child_signals_mask (sigset_t *prev_mask);
\f
/* Trivial list manipulation functions to keep track of a list of
new stopped processes. */
_exit (0);
}
-/* Wrapper function for waitpid which handles EINTR, and checks for
- locally queued events. */
+/* Wrapper function for waitpid which handles EINTR. */
static int
my_waitpid (int pid, int *status, int flags)
{
int ret;
- /* There should be no concurrent calls to waitpid. */
- gdb_assert (linux_nat_async_events_state == sigchld_sync);
-
- ret = queued_waitpid (pid, status, flags);
- if (ret != -1)
- return ret;
-
do
{
ret = waitpid (pid, status, flags);
{
int child_pid, ret, status;
long second_pid;
- enum sigchld_state async_events_original_state;
+ sigset_t prev_mask;
- async_events_original_state = linux_nat_async_events (sigchld_sync);
+ /* We don't want those ptrace calls to be interrupted. */
+ block_child_signals (&prev_mask);
linux_supports_tracefork_flag = 0;
linux_supports_tracevforkdone_flag = 0;
ret = ptrace (PTRACE_SETOPTIONS, original_pid, 0, PTRACE_O_TRACEFORK);
if (ret != 0)
- return;
+ {
+ restore_child_signals_mask (&prev_mask);
+ return;
+ }
child_pid = fork ();
if (child_pid == -1)
if (ret != 0)
{
warning (_("linux_test_for_tracefork: failed to kill child"));
- linux_nat_async_events (async_events_original_state);
+ restore_child_signals_mask (&prev_mask);
return;
}
warning (_("linux_test_for_tracefork: unexpected wait status 0x%x from "
"killed child"), status);
- linux_nat_async_events (async_events_original_state);
+ restore_child_signals_mask (&prev_mask);
return;
}
warning (_("linux_test_for_tracefork: failed to kill child"));
my_waitpid (child_pid, &status, 0);
- linux_nat_async_events (async_events_original_state);
+ restore_child_signals_mask (&prev_mask);
}
/* Return non-zero iff we have tracefork functionality available.
static int
linux_child_follow_fork (struct target_ops *ops, int follow_child)
{
+ sigset_t prev_mask;
ptid_t last_ptid;
struct target_waitstatus last_status;
int has_vforked;
int parent_pid, child_pid;
- if (target_can_async_p ())
- target_async (NULL, 0);
+ block_child_signals (&prev_mask);
get_last_target_status (&last_ptid, &last_status);
has_vforked = (last_status.kind == TARGET_WAITKIND_VFORKED);
follow_inferior_reset_breakpoints ();
}
- if (target_can_async_p ())
- target_async (inferior_event_handler, 0);
-
+ restore_child_signals_mask (&prev_mask);
return 0;
}
_initialize_linux_nat. */
static sigset_t suspend_mask;
-/* SIGCHLD action for synchronous mode. */
-struct sigaction sync_sigchld_action;
+/* Signals to block to make that sigsuspend work. */
+static sigset_t blocked_mask;
+
+/* SIGCHLD action. */
+struct sigaction sigchld_action;
-/* SIGCHLD action for asynchronous mode. */
-static struct sigaction async_sigchld_action;
+/* Block child signals (SIGCHLD and linux threads signals), and store
+ the previous mask in PREV_MASK. */
-/* SIGCHLD default action, to pass to new inferiors. */
-static struct sigaction sigchld_default_action;
+static void
+block_child_signals (sigset_t *prev_mask)
+{
+ /* Make sure SIGCHLD is blocked. */
+ if (!sigismember (&blocked_mask, SIGCHLD))
+ sigaddset (&blocked_mask, SIGCHLD);
+
+ sigprocmask (SIG_BLOCK, &blocked_mask, prev_mask);
+}
+
+/* Restore child signals mask, previously returned by
+ block_child_signals. */
+
+static void
+restore_child_signals_mask (sigset_t *prev_mask)
+{
+ sigprocmask (SIG_SETMASK, prev_mask, NULL);
+}
\f
/* Prototypes for local functions. */
lin_lwp_attach_lwp (ptid_t ptid)
{
struct lwp_info *lp;
- enum sigchld_state async_events_original_state;
+ sigset_t prev_mask;
gdb_assert (is_lwp (ptid));
- async_events_original_state = linux_nat_async_events (sigchld_sync);
+ block_child_signals (&prev_mask);
lp = find_lwp_pid (ptid);
to create them. */
warning (_("Can't attach %s: %s"), target_pid_to_str (ptid),
safe_strerror (errno));
+ restore_child_signals_mask (&prev_mask);
return -1;
}
lp->stopped = 1;
}
- linux_nat_async_events (async_events_original_state);
+ restore_child_signals_mask (&prev_mask);
return 0;
}
/* Mask async mode. Creating a child requires a loop calling
wait_for_inferior currently. */
saved_async = linux_nat_async_mask (0);
- else
- {
- /* Restore the original signal mask. */
- sigprocmask (SIG_SETMASK, &normal_mask, NULL);
- /* Make sure we don't block SIGCHLD during a sigsuspend. */
- suspend_mask = normal_mask;
- sigdelset (&suspend_mask, SIGCHLD);
- }
-
- /* Set SIGCHLD to the default action, until after execing the child,
- since the inferior inherits the superior's signal mask. It will
- be blocked again in linux_nat_wait, which is only reached after
- the inferior execing. */
- linux_nat_async_events (sigchld_default);
#ifdef HAVE_PERSONALITY
if (disable_randomization)
attach all of them. */
linux_ops->to_attach (ops, args, from_tty);
- if (!target_can_async_p ())
- {
- /* Restore the original signal mask. */
- sigprocmask (SIG_SETMASK, &normal_mask, NULL);
- /* Make sure we don't block SIGCHLD during a sigsuspend. */
- suspend_mask = normal_mask;
- sigdelset (&suspend_mask, SIGCHLD);
- }
-
/* The ptrace base target adds the main thread with (pid,0,0)
format. Decorate it with lwp info. */
ptid = BUILD_LWP (GET_PID (inferior_ptid), GET_PID (inferior_ptid));
"LNA: waitpid %ld, saving status %s\n",
(long) GET_PID (lp->ptid), status_to_str (status));
- if (!target_can_async_p ())
- lp->status = status;
- else
- {
- /* We already waited for this LWP, so put the wait result on the
- pipe. The event loop will wake up and gets us to handling
- this event. */
- linux_nat_event_pipe_push (GET_PID (lp->ptid), status,
- lp->cloned ? __WCLONE : 0);
- /* Register in the event loop. */
- target_async (inferior_event_handler, 0);
- }
+ lp->status = status;
+
+ if (target_can_async_p ())
+ target_async (inferior_event_handler, 0);
}
/* Get pending status of LP. */
get_last_target_status (&last_ptid, &last);
/* If this lwp is the ptid that GDB is processing an event from, the
- signal will be in stop_signal. Otherwise, in all-stop + sync
- mode, we may cache pending events in lp->status while trying to
- stop all threads (see stop_wait_callback). In async mode, the
- events are always cached in waitpid_queue. */
+ signal will be in stop_signal. Otherwise, we may cache pending
+ events in lp->status while trying to stop all threads (see
+ stop_wait_callback). */
*status = 0;
stop_wait_callback sequence (see linux_nat_detach for
example) --- we can only have pending events in the local
queue. */
- if (queued_waitpid (GET_LWP (lp->ptid), status, __WALL) != -1)
- {
- if (WIFSTOPPED (*status))
- signo = target_signal_from_host (WSTOPSIG (*status));
-
- /* If not stopped, then the lwp is gone, no use in
- resending a signal. */
- }
+ signo = target_signal_from_host (WSTOPSIG (lp->status));
}
else
{
&& signal_pass_state (tp->stop_signal))
*status = W_STOPCODE (target_signal_to_host (tp->stop_signal));
}
- else if (target_can_async_p ())
- queued_waitpid (GET_LWP (lp->ptid), status, __WALL);
else
*status = lp->status;
}
fprintf_unfiltered (gdb_stdlog,
"PTRACE_DETACH (%s, %s, 0) (OK)\n",
target_pid_to_str (lp->ptid),
- strsignal (WSTOPSIG (lp->status)));
+ strsignal (WSTOPSIG (status)));
delete_lwp (lp->ptid);
}
pid = ptid_get_pid (inferior_ptid);
- if (target_can_async_p ())
- drain_queued_events (pid);
-
if (forks_exist_p ())
{
/* Multi-fork case. The current inferior_ptid is being detached
linux_nat_resume (struct target_ops *ops,
ptid_t ptid, int step, enum target_signal signo)
{
+ sigset_t prev_mask;
struct lwp_info *lp;
int resume_all;
signo ? strsignal (signo) : "0",
target_pid_to_str (inferior_ptid));
- if (target_can_async_p ())
- /* Block events while we're here. */
- linux_nat_async_events (sigchld_sync);
+ block_child_signals (&prev_mask);
/* A specific PTID means `step only this process id'. */
resume_all = (PIDGET (ptid) == -1);
other threads. This bit of code needs to be synchronized
with linux_nat_wait. */
- /* In async mode, we never have pending wait status. */
- if (target_can_async_p () && lp->status)
- internal_error (__FILE__, __LINE__, "Pending status in async mode");
-
if (lp->status && WIFSTOPPED (lp->status))
{
int saved_signo;
"LLR: Short circuiting for status 0x%x\n",
lp->status);
+ restore_child_signals_mask (&prev_mask);
+ if (target_can_async_p ())
+ {
+ target_async (inferior_event_handler, 0);
+ /* Tell the event loop we have something to process. */
+ async_file_mark ();
+ }
return;
}
target_pid_to_str (ptid),
signo ? strsignal (signo) : "0");
+ restore_child_signals_mask (&prev_mask);
if (target_can_async_p ())
target_async (inferior_event_handler, 0);
}
there are any more (we still want to get that SIGSTOP). */
stop_wait_callback (lp, NULL);
- if (target_can_async_p ())
- {
- /* Don't leave a pending wait status in async mode.
- Retrigger the breakpoint. */
- if (!cancel_breakpoint (lp))
- {
- /* There was no gdb breakpoint set at pc. Put
- the event back in the queue. */
- if (debug_linux_nat)
- fprintf_unfiltered (gdb_stdlog, "\
-SWC: leaving SIGTRAP in local queue of %s\n", target_pid_to_str (lp->ptid));
- push_waitpid (GET_LWP (lp->ptid),
- W_STOPCODE (SIGTRAP),
- lp->cloned ? __WCLONE : 0);
- }
- }
- else
+ /* Hold the SIGTRAP for handling by linux_nat_wait. If
+ there's another event, throw it back into the
+ queue. */
+ if (lp->status)
{
- /* Hold the SIGTRAP for handling by
- linux_nat_wait. */
- /* If there's another event, throw it back into the
- queue. */
- if (lp->status)
- {
- if (debug_linux_nat)
- fprintf_unfiltered (gdb_stdlog,
- "SWC: kill %s, %s\n",
- target_pid_to_str (lp->ptid),
- status_to_str ((int) status));
- kill_lwp (GET_LWP (lp->ptid), WSTOPSIG (lp->status));
- }
- /* Save the sigtrap event. */
- lp->status = status;
+ if (debug_linux_nat)
+ fprintf_unfiltered (gdb_stdlog,
+ "SWC: kill %s, %s\n",
+ target_pid_to_str (lp->ptid),
+ status_to_str ((int) status));
+ kill_lwp (GET_LWP (lp->ptid), WSTOPSIG (lp->status));
}
+
+ /* Save the sigtrap event. */
+ lp->status = status;
return 0;
}
else
/* If the lp->status field is still empty, use it to
hold this event. If not, then this event must be
returned to the event queue of the LWP. */
- if (lp->status || target_can_async_p ())
+ if (lp->status)
{
if (debug_linux_nat)
{
return lp;
}
-/* Get the events stored in the pipe into the local queue, so they are
- accessible to queued_waitpid. We need to do this, since it is not
- always the case that the event at the head of the pipe is the event
- we want. */
-
-static void
-pipe_to_local_event_queue (void)
-{
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog,
- "PTLEQ: linux_nat_num_queued_events(%d)\n",
- linux_nat_num_queued_events);
- while (linux_nat_num_queued_events)
- {
- int lwpid, status, options;
- lwpid = linux_nat_event_pipe_pop (&status, &options);
- gdb_assert (lwpid > 0);
- push_waitpid (lwpid, status, options);
- }
-}
-
-/* Get the unprocessed events stored in the local queue back into the
- pipe, so the event loop realizes there's something else to
- process. */
-
-static void
-local_event_queue_to_pipe (void)
-{
- struct waitpid_result *w = waitpid_queue;
- while (w)
- {
- struct waitpid_result *next = w->next;
- linux_nat_event_pipe_push (w->pid,
- w->status,
- w->options);
- xfree (w);
- w = next;
- }
- waitpid_queue = NULL;
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog,
- "LEQTP: linux_nat_num_queued_events(%d)\n",
- linux_nat_num_queued_events);
-}
-
static ptid_t
-linux_nat_wait (struct target_ops *ops,
- ptid_t ptid, struct target_waitstatus *ourstatus)
+linux_nat_wait_1 (struct target_ops *ops,
+ ptid_t ptid, struct target_waitstatus *ourstatus)
{
+ static sigset_t prev_mask;
struct lwp_info *lp = NULL;
int options = 0;
int status = 0;
lp->resumed = 1;
}
- /* Block events while we're here. */
- linux_nat_async_events (sigchld_sync);
+ /* Make sure SIGCHLD is blocked. */
+ block_child_signals (&prev_mask);
retry:
lp = iterate_over_lwps (status_callback, NULL);
if (lp)
{
- if (target_can_async_p ())
- internal_error (__FILE__, __LINE__,
- "Found an LWP with a pending status in async mode.");
-
status = lp->status;
lp->status = 0;
}
/* But if we don't find one, we'll have to wait, and check both
- cloned and uncloned processes. We start with the cloned
- processes. */
+ cloned and uncloned processes. We start with the cloned
+ processes. */
options = __WCLONE | WNOHANG;
}
else if (is_lwp (ptid))
set_sigint_trap ();
}
+ if (target_can_async_p ())
+ options |= WNOHANG; /* In async mode, don't block. */
+
while (status == 0)
{
pid_t lwpid;
- if (target_can_async_p ())
- /* In async mode, don't ever block. Only look at the locally
- queued events. */
- lwpid = queued_waitpid (pid, &status, options);
- else
- lwpid = my_waitpid (pid, &status, options);
+ lwpid = my_waitpid (pid, &status, options);
if (lwpid > 0)
{
/* No interesting event. */
ourstatus->kind = TARGET_WAITKIND_IGNORE;
- /* Get ready for the next event. */
- target_async (inferior_event_handler, 0);
-
if (debug_linux_nat_async)
fprintf_unfiltered (gdb_stdlog, "LLW: exit (ignore)\n");
+ restore_child_signals_mask (&prev_mask);
return minus_one_ptid;
}
else
store_waitstatus (ourstatus, status);
- /* Get ready for the next event. */
- if (target_can_async_p ())
- target_async (inferior_event_handler, 0);
-
if (debug_linux_nat_async)
fprintf_unfiltered (gdb_stdlog, "LLW: exit\n");
+ restore_child_signals_mask (&prev_mask);
return lp->ptid;
}
+static ptid_t
+linux_nat_wait (struct target_ops *ops,
+ ptid_t ptid, struct target_waitstatus *ourstatus)
+{
+ ptid_t event_ptid;
+
+ if (debug_linux_nat)
+ fprintf_unfiltered (gdb_stdlog, "linux_nat_wait: [%s]\n", target_pid_to_str (ptid));
+
+ /* Flush the async file first. */
+ if (target_can_async_p ())
+ async_file_flush ();
+
+ event_ptid = linux_nat_wait_1 (ops, ptid, ourstatus);
+
+ /* If we requested any event, and something came out, assume there
+ may be more. If we requested a specific lwp or process, also
+ assume there may be more. */
+ if (target_can_async_p ()
+ && (ourstatus->kind != TARGET_WAITKIND_IGNORE
+ || !ptid_equal (ptid, minus_one_ptid)))
+ async_file_mark ();
+
+ /* Get ready for the next event. */
+ if (target_can_async_p ())
+ target_async (inferior_event_handler, 0);
+
+ return event_ptid;
+}
+
static int
kill_callback (struct lwp_info *lp, void *data)
{
ptid_t last_ptid;
int status;
- if (target_can_async_p ())
- target_async (NULL, 0);
-
/* If we're stopped while forking and we haven't followed yet,
kill the other task. We need to do this first because the
parent will be sleeping if this is a vfork. */
}
if (forks_exist_p ())
- {
- linux_fork_killall ();
- drain_queued_events (-1);
- }
+ linux_fork_killall ();
else
{
/* Stop all threads before killing them, since ptrace requires
if (! forks_exist_p ())
{
/* Normal case, no other forks available. */
+ linux_ops->to_mourn_inferior (ops);
+
if (target_can_async_p ())
linux_nat_async (NULL, 0);
- linux_ops->to_mourn_inferior (ops);
}
else
/* Multi-fork case. The current inferior_ptid has exited, but
return normal_pid_to_str (ptid);
}
-static void
-sigchld_handler (int signo)
-{
- if (target_async_permitted
- && linux_nat_async_events_state != sigchld_sync
- && signo == SIGCHLD)
- /* It is *always* a bug to hit this. */
- internal_error (__FILE__, __LINE__,
- "sigchld_handler called when async events are enabled");
-
- /* Do nothing. The only reason for this handler is that it allows
- us to use sigsuspend in linux_nat_wait above to wait for the
- arrival of a SIGCHLD. */
-}
-
/* Accepts an integer PID; Returns a string representing a file that
can be opened to get the symbols for the child process. */
linux_nat_is_async_p (void)
{
/* NOTE: palves 2008-03-21: We're only async when the user requests
- it explicitly with the "maintenance set target-async" command.
+ it explicitly with the "set target-async" command.
Someday, linux will always be async. */
if (!target_async_permitted)
return 0;
linux_nat_can_async_p (void)
{
/* NOTE: palves 2008-03-21: We're only async when the user requests
- it explicitly with the "maintenance set target-async" command.
+ it explicitly with the "set target-async" command.
Someday, linux will always be async. */
if (!target_async_permitted)
return 0;
/* target_async_mask implementation. */
static int
-linux_nat_async_mask (int mask)
+linux_nat_async_mask (int new_mask)
{
- int current_state;
- current_state = linux_nat_async_mask_value;
+ int curr_mask = linux_nat_async_mask_value;
- if (current_state != mask)
+ if (curr_mask != new_mask)
{
- if (mask == 0)
+ if (new_mask == 0)
{
linux_nat_async (NULL, 0);
- linux_nat_async_mask_value = mask;
+ linux_nat_async_mask_value = new_mask;
}
else
{
- linux_nat_async_mask_value = mask;
- linux_nat_async (inferior_event_handler, 0);
- }
- }
-
- return current_state;
-}
-
-/* Pop an event from the event pipe. */
-
-static int
-linux_nat_event_pipe_pop (int* ptr_status, int* ptr_options)
-{
- struct waitpid_result event = {0};
- int ret;
-
- do
- {
- ret = read (linux_nat_event_pipe[0], &event, sizeof (event));
- }
- while (ret == -1 && errno == EINTR);
-
- gdb_assert (ret == sizeof (event));
-
- *ptr_status = event.status;
- *ptr_options = event.options;
-
- linux_nat_num_queued_events--;
-
- return event.pid;
-}
-
-/* Push an event into the event pipe. */
-
-static void
-linux_nat_event_pipe_push (int pid, int status, int options)
-{
- int ret;
- struct waitpid_result event = {0};
- event.pid = pid;
- event.status = status;
- event.options = options;
-
- do
- {
- ret = write (linux_nat_event_pipe[1], &event, sizeof (event));
- gdb_assert ((ret == -1 && errno == EINTR) || ret == sizeof (event));
- } while (ret == -1 && errno == EINTR);
-
- linux_nat_num_queued_events++;
-}
-
-static void
-get_pending_events (void)
-{
- int status, options, pid;
-
- if (!target_async_permitted
- || linux_nat_async_events_state != sigchld_async)
- internal_error (__FILE__, __LINE__,
- "get_pending_events called with async masked");
-
- while (1)
- {
- status = 0;
- options = __WCLONE | WNOHANG;
-
- do
- {
- pid = waitpid (-1, &status, options);
- }
- while (pid == -1 && errno == EINTR);
-
- if (pid <= 0)
- {
- options = WNOHANG;
- do
- {
- pid = waitpid (-1, &status, options);
- }
- while (pid == -1 && errno == EINTR);
- }
-
- if (pid <= 0)
- /* No more children reporting events. */
- break;
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog, "\
-get_pending_events: pid(%d), status(%x), options (%x)\n",
- pid, status, options);
-
- linux_nat_event_pipe_push (pid, status, options);
- }
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog, "\
-get_pending_events: linux_nat_num_queued_events(%d)\n",
- linux_nat_num_queued_events);
-}
-
-/* SIGCHLD handler for async mode. */
-
-static void
-async_sigchld_handler (int signo)
-{
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog, "async_sigchld_handler\n");
-
- get_pending_events ();
-}
-
-/* Set SIGCHLD handling state to STATE. Returns previous state. */
-
-static enum sigchld_state
-linux_nat_async_events (enum sigchld_state state)
-{
- enum sigchld_state current_state = linux_nat_async_events_state;
-
- if (debug_linux_nat_async)
- fprintf_unfiltered (gdb_stdlog,
- "LNAE: state(%d): linux_nat_async_events_state(%d), "
- "linux_nat_num_queued_events(%d)\n",
- state, linux_nat_async_events_state,
- linux_nat_num_queued_events);
-
- if (current_state != state)
- {
- sigset_t mask;
- sigemptyset (&mask);
- sigaddset (&mask, SIGCHLD);
-
- /* Always block before changing state. */
- sigprocmask (SIG_BLOCK, &mask, NULL);
-
- /* Set new state. */
- linux_nat_async_events_state = state;
-
- switch (state)
- {
- case sigchld_sync:
- {
- /* Block target events. */
- sigprocmask (SIG_BLOCK, &mask, NULL);
- sigaction (SIGCHLD, &sync_sigchld_action, NULL);
- /* Get events out of queue, and make them available to
- queued_waitpid / my_waitpid. */
- pipe_to_local_event_queue ();
- }
- break;
- case sigchld_async:
- {
- /* Unblock target events for async mode. */
+ linux_nat_async_mask_value = new_mask;
- sigprocmask (SIG_BLOCK, &mask, NULL);
-
- /* Put events we already waited on, in the pipe first, so
- events are FIFO. */
- local_event_queue_to_pipe ();
- /* While in masked async, we may have not collected all
- the pending events. Get them out now. */
- get_pending_events ();
-
- /* Let'em come. */
- sigaction (SIGCHLD, &async_sigchld_action, NULL);
- sigprocmask (SIG_UNBLOCK, &mask, NULL);
- }
- break;
- case sigchld_default:
- {
- /* SIGCHLD default mode. */
- sigaction (SIGCHLD, &sigchld_default_action, NULL);
-
- /* Get events out of queue, and make them available to
- queued_waitpid / my_waitpid. */
- pipe_to_local_event_queue ();
-
- /* Unblock SIGCHLD. */
- sigprocmask (SIG_UNBLOCK, &mask, NULL);
- }
- break;
+ /* If we're going out of async-mask in all-stop, then the
+ inferior is stopped. The next resume will call
+ target_async. In non-stop, the target event source
+ should be always registered in the event loop. Do so
+ now. */
+ if (non_stop)
+ linux_nat_async (inferior_event_handler, 0);
}
}
- return current_state;
+ return curr_mask;
}
static int async_terminal_is_ours = 1;
void *context);
static void *async_client_context;
+/* SIGCHLD handler that serves two purposes: In non-stop/async mode,
+ so we notice when any child changes state, and notify the
+ event-loop; it allows us to use sigsuspend in linux_nat_wait_1
+ above to wait for the arrival of a SIGCHLD. */
+
static void
-linux_nat_async_file_handler (int error, gdb_client_data client_data)
+sigchld_handler (int signo)
{
- async_client_callback (INF_REG_EVENT, async_client_context);
+ int old_errno = errno;
+
+ if (debug_linux_nat_async)
+ fprintf_unfiltered (gdb_stdlog, "sigchld\n");
+
+ if (signo == SIGCHLD
+ && linux_nat_event_pipe[0] != -1)
+ async_file_mark (); /* Let the event loop know that there are
+ events to handle. */
+
+ errno = old_errno;
+}
+
+/* Callback registered with the target events file descriptor. */
+
+static void
+handle_target_event (int error, gdb_client_data client_data)
+{
+ (*async_client_callback) (INF_REG_EVENT, async_client_context);
+}
+
+/* Create/destroy the target events pipe. Returns previous state. */
+
+static int
+linux_async_pipe (int enable)
+{
+ int previous = (linux_nat_event_pipe[0] != -1);
+
+ if (previous != enable)
+ {
+ sigset_t prev_mask;
+
+ block_child_signals (&prev_mask);
+
+ if (enable)
+ {
+ if (pipe (linux_nat_event_pipe) == -1)
+ internal_error (__FILE__, __LINE__,
+ "creating event pipe failed.");
+
+ fcntl (linux_nat_event_pipe[0], F_SETFL, O_NONBLOCK);
+ fcntl (linux_nat_event_pipe[1], F_SETFL, O_NONBLOCK);
+ }
+ else
+ {
+ close (linux_nat_event_pipe[0]);
+ close (linux_nat_event_pipe[1]);
+ linux_nat_event_pipe[0] = -1;
+ linux_nat_event_pipe[1] = -1;
+ }
+
+ restore_child_signals_mask (&prev_mask);
+ }
+
+ return previous;
}
/* target_async implementation. */
{
async_client_callback = callback;
async_client_context = context;
- add_file_handler (linux_nat_event_pipe[0],
- linux_nat_async_file_handler, NULL);
-
- linux_nat_async_events (sigchld_async);
+ if (!linux_async_pipe (1))
+ {
+ add_file_handler (linux_nat_event_pipe[0],
+ handle_target_event, NULL);
+ /* There may be pending events to handle. Tell the event loop
+ to poll them. */
+ async_file_mark ();
+ }
}
else
{
async_client_callback = callback;
async_client_context = context;
-
- linux_nat_async_events (sigchld_sync);
delete_file_handler (linux_nat_event_pipe[0]);
+ linux_async_pipe (0);
}
return;
}
if (!lwp->stopped)
{
int pid, status;
+ ptid_t ptid = lwp->ptid;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LNSL: running -> suspending %s\n",
target_pid_to_str (lwp->ptid));
- /* Peek once, to check if we've already waited for this
- LWP. */
- pid = queued_waitpid_1 (ptid_get_lwp (lwp->ptid), &status,
- lwp->cloned ? __WCLONE : 0, 1 /* peek */);
-
- if (pid == -1)
- {
- ptid_t ptid = lwp->ptid;
-
- stop_callback (lwp, NULL);
- stop_wait_callback (lwp, NULL);
- /* If the lwp exits while we try to stop it, there's
- nothing else to do. */
- lwp = find_lwp_pid (ptid);
- if (lwp == NULL)
- return 0;
+ stop_callback (lwp, NULL);
+ stop_wait_callback (lwp, NULL);
- pid = queued_waitpid_1 (ptid_get_lwp (lwp->ptid), &status,
- lwp->cloned ? __WCLONE : 0,
- 1 /* peek */);
- }
+ /* If the lwp exits while we try to stop it, there's nothing
+ else to do. */
+ lwp = find_lwp_pid (ptid);
+ if (lwp == NULL)
+ return 0;
/* If we didn't collect any signal other than SIGSTOP while
stopping the LWP, push a SIGNAL_0 event. In either case,
the event-loop will end up calling target_wait which will
collect these. */
- if (pid == -1)
- push_waitpid (ptid_get_lwp (lwp->ptid), W_STOPCODE (0),
- lwp->cloned ? __WCLONE : 0);
+ if (lwp->status == 0)
+ lwp->status = W_STOPCODE (0);
+ async_file_mark ();
}
else
{
linux_nat_stop (ptid_t ptid)
{
if (non_stop)
- {
- linux_nat_async_events (sigchld_sync);
- iterate_over_lwps (linux_nat_stop_lwp, &ptid);
- target_async (inferior_event_handler, 0);
- }
+ iterate_over_lwps (linux_nat_stop_lwp, &ptid);
else
linux_ops->to_stop (ptid);
}
return &lp->siginfo;
}
-/* Enable/Disable async mode. */
-
-static void
-linux_nat_setup_async (void)
-{
- if (pipe (linux_nat_event_pipe) == -1)
- internal_error (__FILE__, __LINE__,
- "creating event pipe failed.");
- fcntl (linux_nat_event_pipe[0], F_SETFL, O_NONBLOCK);
- fcntl (linux_nat_event_pipe[1], F_SETFL, O_NONBLOCK);
-}
-
/* Provide a prototype to silence -Wmissing-prototypes. */
extern initialize_file_ftype _initialize_linux_nat;
show_debug_linux_nat_async,
&setdebuglist, &showdebuglist);
- /* Get the default SIGCHLD action. Used while forking an inferior
- (see linux_nat_create_inferior/linux_nat_async_events). */
- sigaction (SIGCHLD, NULL, &sigchld_default_action);
-
- /* Block SIGCHLD by default. Doing this early prevents it getting
- unblocked if an exception is thrown due to an error while the
- inferior is starting (sigsetjmp/siglongjmp). */
- sigemptyset (&mask);
- sigaddset (&mask, SIGCHLD);
- sigprocmask (SIG_BLOCK, &mask, NULL);
-
/* Save this mask as the default. */
sigprocmask (SIG_SETMASK, NULL, &normal_mask);
- /* The synchronous SIGCHLD handler. */
- sync_sigchld_action.sa_handler = sigchld_handler;
- sigemptyset (&sync_sigchld_action.sa_mask);
- sync_sigchld_action.sa_flags = SA_RESTART;
+ /* Install a SIGCHLD handler. */
+ sigchld_action.sa_handler = sigchld_handler;
+ sigemptyset (&sigchld_action.sa_mask);
+ sigchld_action.sa_flags = SA_RESTART;
/* Make it the default. */
- sigaction (SIGCHLD, &sync_sigchld_action, NULL);
+ sigaction (SIGCHLD, &sigchld_action, NULL);
/* Make sure we don't block SIGCHLD during a sigsuspend. */
sigprocmask (SIG_SETMASK, NULL, &suspend_mask);
sigdelset (&suspend_mask, SIGCHLD);
- /* SIGCHLD handler for async mode. */
- async_sigchld_action.sa_handler = async_sigchld_handler;
- sigemptyset (&async_sigchld_action.sa_mask);
- async_sigchld_action.sa_flags = SA_RESTART;
-
- linux_nat_setup_async ();
+ sigemptyset (&blocked_mask);
add_setshow_boolean_cmd ("disable-randomization", class_support,
&disable_randomization, _("\
{
struct sigaction action;
int restart, cancel;
- sigset_t blocked_mask;
sigemptyset (&blocked_mask);
sigemptyset (set);
projects / binutils-gdb.git / commitdiff