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/*
* Copyright © 2011 Canonical Limited
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
* Author: Ryan Lortie <desrt@desrt.ca>
*/
#include "config.h"
#include <stdint.h>
/* gwakeup.c is special -- GIO and some test cases include it. As such,
* it cannot include other glib headers without triggering the single
* includes warnings. We have to manually include its dependencies here
* (and at all other use sites).
*/
#ifdef GLIB_COMPILATION
#include "gtypes.h"
#include "gpoll.h"
#else
#include <glib.h>
#endif
#include "gwakeup.h"
/*< private >
* GWakeup:
*
* `GWakeup` is a simple and portable way of signaling events between
* different threads in a way that integrates nicely with g_poll().
* GLib uses it internally for cross-thread signalling in the
* implementation of #GMainContext and #GCancellable.
*
* You first create a #GWakeup with g_wakeup_new() and initialise a
* #GPollFD from it using g_wakeup_get_pollfd(). Polling on the created
* #GPollFD will block until g_wakeup_signal() is called, at which point
* it will immediately return. Future attempts to poll will continue to
* return until g_wakeup_acknowledge() is called. g_wakeup_free() is
* used to free a #GWakeup.
*
* On sufficiently modern Linux, this is implemented using eventfd. On
* Windows it is implemented using an event handle. On other systems it
* is implemented with a pair of pipes.
*
* Since: 2.30
*/
#ifdef _WIN32
#include <windows.h>
#ifdef GLIB_COMPILATION
#include "gmessages.h"
#include "giochannel.h"
#include "gwin32.h"
#endif
GWakeup *
g_wakeup_new (void)
{
HANDLE wakeup;
wakeup = CreateEvent (NULL, TRUE, FALSE, NULL);
if (wakeup == NULL)
g_error ("Cannot create event for GWakeup: %s",
g_win32_error_message (GetLastError ()));
return (GWakeup *) wakeup;
}
void
g_wakeup_get_pollfd (GWakeup *wakeup,
GPollFD *poll_fd)
{
poll_fd->fd = (gintptr) wakeup;
poll_fd->events = G_IO_IN;
}
void
g_wakeup_acknowledge (GWakeup *wakeup)
{
ResetEvent ((HANDLE) wakeup);
}
void
g_wakeup_signal (GWakeup *wakeup)
{
SetEvent ((HANDLE) wakeup);
}
void
g_wakeup_free (GWakeup *wakeup)
{
CloseHandle ((HANDLE) wakeup);
}
#else
#include "glib-unix.h"
#include <fcntl.h>
#if defined (HAVE_EVENTFD)
#include <sys/eventfd.h>
#endif
struct _GWakeup
{
gint fds[2];
};
/*< private >
* g_wakeup_new:
*
* Creates a new #GWakeup.
*
* You should use g_wakeup_free() to free it when you are done.
*
* Returns: a new #GWakeup
*
* Since: 2.30
**/
GWakeup *
g_wakeup_new (void)
{
GError *error = NULL;
GWakeup *wakeup;
wakeup = g_slice_new (GWakeup);
/* try eventfd first, if we think we can */
#if defined (HAVE_EVENTFD)
#ifndef TEST_EVENTFD_FALLBACK
wakeup->fds[0] = eventfd (0, EFD_CLOEXEC | EFD_NONBLOCK);
#else
wakeup->fds[0] = -1;
#endif
if (wakeup->fds[0] != -1)
{
wakeup->fds[1] = -1;
return wakeup;
}
/* for any failure, try a pipe instead */
#endif
if (!g_unix_open_pipe (wakeup->fds, O_CLOEXEC | O_NONBLOCK, &error))
g_error ("Creating pipes for GWakeup: %s", error->message);
if (!g_unix_set_fd_nonblocking (wakeup->fds[0], TRUE, &error) ||
!g_unix_set_fd_nonblocking (wakeup->fds[1], TRUE, &error))
g_error ("Set pipes non-blocking for GWakeup: %s", error->message);
return wakeup;
}
/*< private >
* g_wakeup_get_pollfd:
* @wakeup: a #GWakeup
* @poll_fd: a #GPollFD
*
* Prepares a @poll_fd such that polling on it will succeed when
* g_wakeup_signal() has been called on @wakeup.
*
* @poll_fd is valid until @wakeup is freed.
*
* Since: 2.30
**/
void
g_wakeup_get_pollfd (GWakeup *wakeup,
GPollFD *poll_fd)
{
poll_fd->fd = wakeup->fds[0];
poll_fd->events = G_IO_IN;
}
/*< private >
* g_wakeup_acknowledge:
* @wakeup: a #GWakeup
*
* Acknowledges receipt of a wakeup signal on @wakeup.
*
* You must call this after @wakeup polls as ready. If not, it will
* continue to poll as ready until you do so.
*
* If you call this function and @wakeup is not signaled, nothing
* happens.
*
* Since: 2.30
**/
void
g_wakeup_acknowledge (GWakeup *wakeup)
{
int res;
if (wakeup->fds[1] == -1)
{
uint64_t value;
/* eventfd() read resets counter */
do
res = read (wakeup->fds[0], &value, sizeof (value));
while (G_UNLIKELY (res == -1 && errno == EINTR));
}
else
{
uint8_t value;
/* read until it is empty */
do
res = read (wakeup->fds[0], &value, sizeof (value));
while (res == sizeof (value) || G_UNLIKELY (res == -1 && errno == EINTR));
}
}
/*< private >
* g_wakeup_signal:
* @wakeup: a #GWakeup
*
* Signals @wakeup.
*
* Any future (or present) polling on the #GPollFD returned by
* g_wakeup_get_pollfd() will immediately succeed until such a time as
* g_wakeup_acknowledge() is called.
*
* This function is safe to call from a UNIX signal handler.
*
* Since: 2.30
**/
void
g_wakeup_signal (GWakeup *wakeup)
{
int res;
if (wakeup->fds[1] == -1)
{
uint64_t one = 1;
/* eventfd() case. It requires a 64-bit counter increment value to be
* written. */
do
res = write (wakeup->fds[0], &one, sizeof one);
while (G_UNLIKELY (res == -1 && errno == EINTR));
}
else
{
uint8_t one = 1;
/* Non-eventfd() case. Only a single byte needs to be written, and it can
* have an arbitrary value. */
do
res = write (wakeup->fds[1], &one, sizeof one);
while (G_UNLIKELY (res == -1 && errno == EINTR));
}
}
/*< private >
* g_wakeup_free:
* @wakeup: a #GWakeup
*
* Frees @wakeup.
*
* You must not currently be polling on the #GPollFD returned by
* g_wakeup_get_pollfd(), or the result is undefined.
**/
void
g_wakeup_free (GWakeup *wakeup)
{
close (wakeup->fds[0]);
if (wakeup->fds[1] != -1)
close (wakeup->fds[1]);
g_slice_free (GWakeup, wakeup);
}
#endif /* !_WIN32 */