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|
/* Event loop machinery for GDB, the GNU debugger.
Copyright (C) 1999-2022 Free Software Foundation, Inc.
Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "gdbsupport/common-defs.h"
#include "gdbsupport/event-loop.h"
#include <chrono>
#ifdef HAVE_POLL
#if defined (HAVE_POLL_H)
#include <poll.h>
#elif defined (HAVE_SYS_POLL_H)
#include <sys/poll.h>
#endif
#endif
#include <sys/types.h>
#include "gdbsupport/gdb_sys_time.h"
#include "gdbsupport/gdb_select.h"
/* See event-loop.h. */
debug_event_loop_kind debug_event_loop;
/* Tell create_file_handler what events we are interested in.
This is used by the select version of the event loop. */
#define GDB_READABLE (1<<1)
#define GDB_WRITABLE (1<<2)
#define GDB_EXCEPTION (1<<3)
/* Information about each file descriptor we register with the event
loop. */
struct file_handler
{
/* File descriptor. */
int fd;
/* Events we want to monitor: POLLIN, etc. */
int mask;
/* Events that have been seen since the last time. */
int ready_mask;
/* Procedure to call when fd is ready. */
handler_func *proc;
/* Argument to pass to proc. */
gdb_client_data client_data;
/* User-friendly name of this handler. */
std::string name;
/* If set, this file descriptor is used for a user interface. */
bool is_ui;
/* Was an error detected on this fd? */
int error;
/* Next registered file descriptor. */
struct file_handler *next_file;
};
#ifdef HAVE_POLL
/* Do we use poll or select? Some systems have poll, but then it's
not useable with all kinds of files. We probe that whenever a new
file handler is added. */
static bool use_poll = true;
#endif
#ifdef USE_WIN32API
#include <windows.h>
#include <io.h>
#endif
/* Gdb_notifier is just a list of file descriptors gdb is interested in.
These are the input file descriptor, and the target file
descriptor. We have two flavors of the notifier, one for platforms
that have the POLL function, the other for those that don't, and
only support SELECT. Each of the elements in the gdb_notifier list is
basically a description of what kind of events gdb is interested
in, for each fd. */
static struct
{
/* Ptr to head of file handler list. */
file_handler *first_file_handler;
/* Next file handler to handle, for the select variant. To level
the fairness across event sources, we serve file handlers in a
round-robin-like fashion. The number and order of the polled
file handlers may change between invocations, but this is good
enough. */
file_handler *next_file_handler;
#ifdef HAVE_POLL
/* Ptr to array of pollfd structures. */
struct pollfd *poll_fds;
/* Next file descriptor to handle, for the poll variant. To level
the fairness across event sources, we poll the file descriptors
in a round-robin-like fashion. The number and order of the
polled file descriptors may change between invocations, but
this is good enough. */
int next_poll_fds_index;
/* Timeout in milliseconds for calls to poll(). */
int poll_timeout;
#endif
/* Masks to be used in the next call to select.
Bits are set in response to calls to create_file_handler. */
fd_set check_masks[3];
/* What file descriptors were found ready by select. */
fd_set ready_masks[3];
/* Number of file descriptors to monitor (for poll). */
/* Number of valid bits (highest fd value + 1) (for select). */
int num_fds;
/* Time structure for calls to select(). */
struct timeval select_timeout;
/* Flag to tell whether the timeout should be used. */
int timeout_valid;
}
gdb_notifier;
/* Structure associated with a timer. PROC will be executed at the
first occasion after WHEN. */
struct gdb_timer
{
std::chrono::steady_clock::time_point when;
int timer_id;
struct gdb_timer *next;
timer_handler_func *proc; /* Function to call to do the work. */
gdb_client_data client_data; /* Argument to async_handler_func. */
};
/* List of currently active timers. It is sorted in order of
increasing timers. */
static struct
{
/* Pointer to first in timer list. */
struct gdb_timer *first_timer;
/* Id of the last timer created. */
int num_timers;
}
timer_list;
static void create_file_handler (int fd, int mask, handler_func *proc,
gdb_client_data client_data,
std::string &&name, bool is_ui);
static int gdb_wait_for_event (int);
static int update_wait_timeout (void);
static int poll_timers (void);
/* Process one high level event. If nothing is ready at this time,
wait for something to happen (via gdb_wait_for_event), then process
it. Returns >0 if something was done otherwise returns <0 (this
can happen if there are no event sources to wait for). */
int
gdb_do_one_event (void)
{
static int event_source_head = 0;
const int number_of_sources = 3;
int current = 0;
/* First let's see if there are any asynchronous signal handlers
that are ready. These would be the result of invoking any of the
signal handlers. */
if (invoke_async_signal_handlers ())
return 1;
/* To level the fairness across event sources, we poll them in a
round-robin fashion. */
for (current = 0; current < number_of_sources; current++)
{
int res;
switch (event_source_head)
{
case 0:
/* Are any timers that are ready? */
res = poll_timers ();
break;
case 1:
/* Are there events already waiting to be collected on the
monitored file descriptors? */
res = gdb_wait_for_event (0);
break;
case 2:
/* Are there any asynchronous event handlers ready? */
res = check_async_event_handlers ();
break;
default:
internal_error (__FILE__, __LINE__,
"unexpected event_source_head %d",
event_source_head);
}
event_source_head++;
if (event_source_head == number_of_sources)
event_source_head = 0;
if (res > 0)
return 1;
}
/* Block waiting for a new event. If gdb_wait_for_event returns -1,
we should get out because this means that there are no event
sources left. This will make the event loop stop, and the
application exit. */
if (gdb_wait_for_event (1) < 0)
return -1;
/* If gdb_wait_for_event has returned 1, it means that one event has
been handled. We break out of the loop. */
return 1;
}
/* See event-loop.h */
void
add_file_handler (int fd, handler_func *proc, gdb_client_data client_data,
std::string &&name, bool is_ui)
{
#ifdef HAVE_POLL
if (use_poll)
{
struct pollfd fds;
/* Check to see if poll () is usable. If not, we'll switch to
use select. This can happen on systems like
m68k-motorola-sys, `poll' cannot be used to wait for `stdin'.
On m68k-motorola-sysv, tty's are not stream-based and not
`poll'able. */
fds.fd = fd;
fds.events = POLLIN;
if (poll (&fds, 1, 0) == 1 && (fds.revents & POLLNVAL))
use_poll = false;
}
if (use_poll)
{
create_file_handler (fd, POLLIN, proc, client_data, std::move (name),
is_ui);
}
else
#endif /* HAVE_POLL */
create_file_handler (fd, GDB_READABLE | GDB_EXCEPTION,
proc, client_data, std::move (name), is_ui);
}
/* Helper for add_file_handler.
For the poll case, MASK is a combination (OR) of POLLIN,
POLLRDNORM, POLLRDBAND, POLLPRI, POLLOUT, POLLWRNORM, POLLWRBAND:
these are the events we are interested in. If any of them occurs,
proc should be called.
For the select case, MASK is a combination of READABLE, WRITABLE,
EXCEPTION. PROC is the procedure that will be called when an event
occurs for FD. CLIENT_DATA is the argument to pass to PROC. */
static void
create_file_handler (int fd, int mask, handler_func * proc,
gdb_client_data client_data, std::string &&name,
bool is_ui)
{
file_handler *file_ptr;
/* Do we already have a file handler for this file? (We may be
changing its associated procedure). */
for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
file_ptr = file_ptr->next_file)
{
if (file_ptr->fd == fd)
break;
}
/* It is a new file descriptor. Add it to the list. Otherwise, just
change the data associated with it. */
if (file_ptr == NULL)
{
file_ptr = new file_handler;
file_ptr->fd = fd;
file_ptr->ready_mask = 0;
file_ptr->next_file = gdb_notifier.first_file_handler;
gdb_notifier.first_file_handler = file_ptr;
#ifdef HAVE_POLL
if (use_poll)
{
gdb_notifier.num_fds++;
if (gdb_notifier.poll_fds)
gdb_notifier.poll_fds =
(struct pollfd *) xrealloc (gdb_notifier.poll_fds,
(gdb_notifier.num_fds
* sizeof (struct pollfd)));
else
gdb_notifier.poll_fds =
XNEW (struct pollfd);
(gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->fd = fd;
(gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->events = mask;
(gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->revents = 0;
}
else
#endif /* HAVE_POLL */
{
if (mask & GDB_READABLE)
FD_SET (fd, &gdb_notifier.check_masks[0]);
else
FD_CLR (fd, &gdb_notifier.check_masks[0]);
if (mask & GDB_WRITABLE)
FD_SET (fd, &gdb_notifier.check_masks[1]);
else
FD_CLR (fd, &gdb_notifier.check_masks[1]);
if (mask & GDB_EXCEPTION)
FD_SET (fd, &gdb_notifier.check_masks[2]);
else
FD_CLR (fd, &gdb_notifier.check_masks[2]);
if (gdb_notifier.num_fds <= fd)
gdb_notifier.num_fds = fd + 1;
}
}
file_ptr->proc = proc;
file_ptr->client_data = client_data;
file_ptr->mask = mask;
file_ptr->name = std::move (name);
file_ptr->is_ui = is_ui;
}
/* Return the next file handler to handle, and advance to the next
file handler, wrapping around if the end of the list is
reached. */
static file_handler *
get_next_file_handler_to_handle_and_advance (void)
{
file_handler *curr_next;
/* The first time around, this is still NULL. */
if (gdb_notifier.next_file_handler == NULL)
gdb_notifier.next_file_handler = gdb_notifier.first_file_handler;
curr_next = gdb_notifier.next_file_handler;
gdb_assert (curr_next != NULL);
/* Advance. */
gdb_notifier.next_file_handler = curr_next->next_file;
/* Wrap around, if necessary. */
if (gdb_notifier.next_file_handler == NULL)
gdb_notifier.next_file_handler = gdb_notifier.first_file_handler;
return curr_next;
}
/* Remove the file descriptor FD from the list of monitored fd's:
i.e. we don't care anymore about events on the FD. */
void
delete_file_handler (int fd)
{
file_handler *file_ptr, *prev_ptr = NULL;
int i;
/* Find the entry for the given file. */
for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
file_ptr = file_ptr->next_file)
{
if (file_ptr->fd == fd)
break;
}
if (file_ptr == NULL)
return;
#ifdef HAVE_POLL
if (use_poll)
{
int j;
struct pollfd *new_poll_fds;
/* Create a new poll_fds array by copying every fd's information
but the one we want to get rid of. */
new_poll_fds = (struct pollfd *)
xmalloc ((gdb_notifier.num_fds - 1) * sizeof (struct pollfd));
for (i = 0, j = 0; i < gdb_notifier.num_fds; i++)
{
if ((gdb_notifier.poll_fds + i)->fd != fd)
{
(new_poll_fds + j)->fd = (gdb_notifier.poll_fds + i)->fd;
(new_poll_fds + j)->events = (gdb_notifier.poll_fds + i)->events;
(new_poll_fds + j)->revents
= (gdb_notifier.poll_fds + i)->revents;
j++;
}
}
xfree (gdb_notifier.poll_fds);
gdb_notifier.poll_fds = new_poll_fds;
gdb_notifier.num_fds--;
}
else
#endif /* HAVE_POLL */
{
if (file_ptr->mask & GDB_READABLE)
FD_CLR (fd, &gdb_notifier.check_masks[0]);
if (file_ptr->mask & GDB_WRITABLE)
FD_CLR (fd, &gdb_notifier.check_masks[1]);
if (file_ptr->mask & GDB_EXCEPTION)
FD_CLR (fd, &gdb_notifier.check_masks[2]);
/* Find current max fd. */
if ((fd + 1) == gdb_notifier.num_fds)
{
gdb_notifier.num_fds--;
for (i = gdb_notifier.num_fds; i; i--)
{
if (FD_ISSET (i - 1, &gdb_notifier.check_masks[0])
|| FD_ISSET (i - 1, &gdb_notifier.check_masks[1])
|| FD_ISSET (i - 1, &gdb_notifier.check_masks[2]))
break;
}
gdb_notifier.num_fds = i;
}
}
/* Deactivate the file descriptor, by clearing its mask,
so that it will not fire again. */
file_ptr->mask = 0;
/* If this file handler was going to be the next one to be handled,
advance to the next's next, if any. */
if (gdb_notifier.next_file_handler == file_ptr)
{
if (file_ptr->next_file == NULL
&& file_ptr == gdb_notifier.first_file_handler)
gdb_notifier.next_file_handler = NULL;
else
get_next_file_handler_to_handle_and_advance ();
}
/* Get rid of the file handler in the file handler list. */
if (file_ptr == gdb_notifier.first_file_handler)
gdb_notifier.first_file_handler = file_ptr->next_file;
else
{
for (prev_ptr = gdb_notifier.first_file_handler;
prev_ptr->next_file != file_ptr;
prev_ptr = prev_ptr->next_file)
;
prev_ptr->next_file = file_ptr->next_file;
}
delete file_ptr;
}
/* Handle the given event by calling the procedure associated to the
corresponding file handler. */
static void
handle_file_event (file_handler *file_ptr, int ready_mask)
{
int mask;
{
{
/* With poll, the ready_mask could have any of three events
set to 1: POLLHUP, POLLERR, POLLNVAL. These events
cannot be used in the requested event mask (events), but
they can be returned in the return mask (revents). We
need to check for those event too, and add them to the
mask which will be passed to the handler. */
/* See if the desired events (mask) match the received
events (ready_mask). */
#ifdef HAVE_POLL
if (use_poll)
{
int error_mask;
/* POLLHUP means EOF, but can be combined with POLLIN to
signal more data to read. */
error_mask = POLLHUP | POLLERR | POLLNVAL;
mask = ready_mask & (file_ptr->mask | error_mask);
if ((mask & (POLLERR | POLLNVAL)) != 0)
{
/* Work in progress. We may need to tell somebody
what kind of error we had. */
if (mask & POLLERR)
warning (_("Error detected on fd %d"), file_ptr->fd);
if (mask & POLLNVAL)
warning (_("Invalid or non-`poll'able fd %d"),
file_ptr->fd);
file_ptr->error = 1;
}
else
file_ptr->error = 0;
}
else
#endif /* HAVE_POLL */
{
if (ready_mask & GDB_EXCEPTION)
{
warning (_("Exception condition detected on fd %d"),
file_ptr->fd);
file_ptr->error = 1;
}
else
file_ptr->error = 0;
mask = ready_mask & file_ptr->mask;
}
/* If there was a match, then call the handler. */
if (mask != 0)
{
event_loop_ui_debug_printf (file_ptr->is_ui,
"invoking fd file handler `%s`",
file_ptr->name.c_str ());
file_ptr->proc (file_ptr->error, file_ptr->client_data);
}
}
}
}
/* Wait for new events on the monitored file descriptors. Run the
event handler if the first descriptor that is detected by the poll.
If BLOCK and if there are no events, this function will block in
the call to poll. Return 1 if an event was handled. Return -1 if
there are no file descriptors to monitor. Return 1 if an event was
handled, otherwise returns 0. */
static int
gdb_wait_for_event (int block)
{
file_handler *file_ptr;
int num_found = 0;
/* Make sure all output is done before getting another event. */
flush_streams ();
if (gdb_notifier.num_fds == 0)
return -1;
if (block)
update_wait_timeout ();
#ifdef HAVE_POLL
if (use_poll)
{
int timeout;
if (block)
timeout = gdb_notifier.timeout_valid ? gdb_notifier.poll_timeout : -1;
else
timeout = 0;
num_found = poll (gdb_notifier.poll_fds,
(unsigned long) gdb_notifier.num_fds, timeout);
/* Don't print anything if we get out of poll because of a
signal. */
if (num_found == -1 && errno != EINTR)
perror_with_name (("poll"));
}
else
#endif /* HAVE_POLL */
{
struct timeval select_timeout;
struct timeval *timeout_p;
if (block)
timeout_p = gdb_notifier.timeout_valid
? &gdb_notifier.select_timeout : NULL;
else
{
memset (&select_timeout, 0, sizeof (select_timeout));
timeout_p = &select_timeout;
}
gdb_notifier.ready_masks[0] = gdb_notifier.check_masks[0];
gdb_notifier.ready_masks[1] = gdb_notifier.check_masks[1];
gdb_notifier.ready_masks[2] = gdb_notifier.check_masks[2];
num_found = gdb_select (gdb_notifier.num_fds,
&gdb_notifier.ready_masks[0],
&gdb_notifier.ready_masks[1],
&gdb_notifier.ready_masks[2],
timeout_p);
/* Clear the masks after an error from select. */
if (num_found == -1)
{
FD_ZERO (&gdb_notifier.ready_masks[0]);
FD_ZERO (&gdb_notifier.ready_masks[1]);
FD_ZERO (&gdb_notifier.ready_masks[2]);
/* Dont print anything if we got a signal, let gdb handle
it. */
if (errno != EINTR)
perror_with_name (("select"));
}
}
/* Avoid looking at poll_fds[i]->revents if no event fired. */
if (num_found <= 0)
return 0;
/* Run event handlers. We always run just one handler and go back
to polling, in case a handler changes the notifier list. Since
events for sources we haven't consumed yet wake poll/select
immediately, no event is lost. */
/* To level the fairness across event descriptors, we handle them in
a round-robin-like fashion. The number and order of descriptors
may change between invocations, but this is good enough. */
#ifdef HAVE_POLL
if (use_poll)
{
int i;
int mask;
while (1)
{
if (gdb_notifier.next_poll_fds_index >= gdb_notifier.num_fds)
gdb_notifier.next_poll_fds_index = 0;
i = gdb_notifier.next_poll_fds_index++;
gdb_assert (i < gdb_notifier.num_fds);
if ((gdb_notifier.poll_fds + i)->revents)
break;
}
for (file_ptr = gdb_notifier.first_file_handler;
file_ptr != NULL;
file_ptr = file_ptr->next_file)
{
if (file_ptr->fd == (gdb_notifier.poll_fds + i)->fd)
break;
}
gdb_assert (file_ptr != NULL);
mask = (gdb_notifier.poll_fds + i)->revents;
handle_file_event (file_ptr, mask);
return 1;
}
else
#endif /* HAVE_POLL */
{
/* See comment about even source fairness above. */
int mask = 0;
do
{
file_ptr = get_next_file_handler_to_handle_and_advance ();
if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[0]))
mask |= GDB_READABLE;
if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[1]))
mask |= GDB_WRITABLE;
if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[2]))
mask |= GDB_EXCEPTION;
}
while (mask == 0);
handle_file_event (file_ptr, mask);
return 1;
}
return 0;
}
/* Create a timer that will expire in MS milliseconds from now. When
the timer is ready, PROC will be executed. At creation, the timer
is added to the timers queue. This queue is kept sorted in order
of increasing timers. Return a handle to the timer struct. */
int
create_timer (int ms, timer_handler_func *proc,
gdb_client_data client_data)
{
using namespace std::chrono;
struct gdb_timer *timer_ptr, *timer_index, *prev_timer;
steady_clock::time_point time_now = steady_clock::now ();
timer_ptr = new gdb_timer ();
timer_ptr->when = time_now + milliseconds (ms);
timer_ptr->proc = proc;
timer_ptr->client_data = client_data;
timer_list.num_timers++;
timer_ptr->timer_id = timer_list.num_timers;
/* Now add the timer to the timer queue, making sure it is sorted in
increasing order of expiration. */
for (timer_index = timer_list.first_timer;
timer_index != NULL;
timer_index = timer_index->next)
{
if (timer_index->when > timer_ptr->when)
break;
}
if (timer_index == timer_list.first_timer)
{
timer_ptr->next = timer_list.first_timer;
timer_list.first_timer = timer_ptr;
}
else
{
for (prev_timer = timer_list.first_timer;
prev_timer->next != timer_index;
prev_timer = prev_timer->next)
;
prev_timer->next = timer_ptr;
timer_ptr->next = timer_index;
}
gdb_notifier.timeout_valid = 0;
return timer_ptr->timer_id;
}
/* There is a chance that the creator of the timer wants to get rid of
it before it expires. */
void
delete_timer (int id)
{
struct gdb_timer *timer_ptr, *prev_timer = NULL;
/* Find the entry for the given timer. */
for (timer_ptr = timer_list.first_timer; timer_ptr != NULL;
timer_ptr = timer_ptr->next)
{
if (timer_ptr->timer_id == id)
break;
}
if (timer_ptr == NULL)
return;
/* Get rid of the timer in the timer list. */
if (timer_ptr == timer_list.first_timer)
timer_list.first_timer = timer_ptr->next;
else
{
for (prev_timer = timer_list.first_timer;
prev_timer->next != timer_ptr;
prev_timer = prev_timer->next)
;
prev_timer->next = timer_ptr->next;
}
delete timer_ptr;
gdb_notifier.timeout_valid = 0;
}
/* Convert a std::chrono duration to a struct timeval. */
template<typename Duration>
static struct timeval
duration_cast_timeval (const Duration &d)
{
using namespace std::chrono;
seconds sec = duration_cast<seconds> (d);
microseconds msec = duration_cast<microseconds> (d - sec);
struct timeval tv;
tv.tv_sec = sec.count ();
tv.tv_usec = msec.count ();
return tv;
}
/* Update the timeout for the select() or poll(). Returns true if the
timer has already expired, false otherwise. */
static int
update_wait_timeout (void)
{
if (timer_list.first_timer != NULL)
{
using namespace std::chrono;
steady_clock::time_point time_now = steady_clock::now ();
struct timeval timeout;
if (timer_list.first_timer->when < time_now)
{
/* It expired already. */
timeout.tv_sec = 0;
timeout.tv_usec = 0;
}
else
{
steady_clock::duration d = timer_list.first_timer->when - time_now;
timeout = duration_cast_timeval (d);
}
/* Update the timeout for select/ poll. */
#ifdef HAVE_POLL
if (use_poll)
gdb_notifier.poll_timeout = timeout.tv_sec * 1000;
else
#endif /* HAVE_POLL */
{
gdb_notifier.select_timeout.tv_sec = timeout.tv_sec;
gdb_notifier.select_timeout.tv_usec = timeout.tv_usec;
}
gdb_notifier.timeout_valid = 1;
if (timer_list.first_timer->when < time_now)
return 1;
}
else
gdb_notifier.timeout_valid = 0;
return 0;
}
/* Check whether a timer in the timers queue is ready. If a timer is
ready, call its handler and return. Update the timeout for the
select() or poll() as well. Return 1 if an event was handled,
otherwise returns 0.*/
static int
poll_timers (void)
{
if (update_wait_timeout ())
{
struct gdb_timer *timer_ptr = timer_list.first_timer;
timer_handler_func *proc = timer_ptr->proc;
gdb_client_data client_data = timer_ptr->client_data;
/* Get rid of the timer from the beginning of the list. */
timer_list.first_timer = timer_ptr->next;
/* Delete the timer before calling the callback, not after, in
case the callback itself decides to try deleting the timer
too. */
delete timer_ptr;
/* Call the procedure associated with that timer. */
(proc) (client_data);
return 1;
}
return 0;
}
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