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GCancellable: Use Linux eventfd() instead of pipe

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See commit f626dd2b4311bd82137c5b208ab2de288c3e6fae for rationale;
basically it's cheaper than a pipe.

https://bugzilla.gnome.org/show_bug.cgi?id=653140
This commit is contained in:
Colin Walters 2011-06-21 21:43:19 -04:00
parent 3904c8761a
commit fa87399280
1 changed files with 68 additions and 20 deletions
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80
gio/gcancellable.c
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@ -24,6 +24,9 @@
#include "glib.h"
#ifdef G_OS_UNIX
#include "glib-unix.h"
#ifdef HAVE_EVENTFD
#include <sys/eventfd.h>
#endif
#endif
#include <gioerror.h>
#ifdef G_OS_WIN32
@ -57,6 +60,7 @@ struct _GCancellablePrivate
guint cancelled_running_waiting : 1;
guint fd_refcount;
/* If cancel_pipe[0] is != -1 and cancel_pipe[1] is -1, it is an eventfd */
int cancel_pipe[2];
#ifdef G_OS_WIN32
@ -193,12 +197,56 @@ g_cancellable_class_init (GCancellableClass *klass)
#ifndef G_OS_WIN32
static void
g_cancellable_write_cancelled (GCancellable *cancellable)
{
gssize c;
GCancellablePrivate *priv;
const char ch = 'x';
priv = cancellable->priv;
if (priv->cancel_pipe[0] == -1)
return;
g_assert (cancellable->priv->cancelled);
#ifdef HAVE_EVENTFD
if (priv->cancel_pipe[1] == -1)
{
guint64 buf = 1;
do
c = write (priv->cancel_pipe[0], &buf, sizeof (buf));
while (c == -1 && errno == EINTR);
return;
}
#endif
do
c = write (priv->cancel_pipe[1], &ch, 1);
while (c == -1 && errno == EINTR);
}
static void
g_cancellable_open_pipe (GCancellable *cancellable)
{
GCancellablePrivate *priv;
priv = cancellable->priv;
#ifdef HAVE_EVENTFD
priv->cancel_pipe[0] = eventfd (0, EFD_CLOEXEC | EFD_NONBLOCK);
if (priv->cancel_pipe[0] >= 0)
{
if (priv->cancelled)
g_cancellable_write_cancelled (cancellable);
return;
}
else if (errno != ENOSYS)
return;
/* Fall through on ENOSYS */
#endif
if (g_unix_open_pipe (priv->cancel_pipe, FD_CLOEXEC, NULL))
{
/* Make them nonblocking, just to be sure we don't block
@ -208,14 +256,7 @@ g_cancellable_open_pipe (GCancellable *cancellable)
g_unix_set_fd_nonblocking (priv->cancel_pipe[1], TRUE, NULL);
if (priv->cancelled)
{
const char ch = 'x';
gssize c;
do
c = write (priv->cancel_pipe[1], &ch, 1);
while (c == -1 && errno == EINTR);
}
g_cancellable_write_cancelled (cancellable);
}
}
#endif
@ -351,12 +392,25 @@ g_cancellable_reset (GCancellable *cancellable)
if (priv->cancel_pipe[0] != -1)
{
gssize c;
#ifdef HAVE_EVENTFD
if (priv->cancel_pipe[1] == -1)
{
guint64 buf;
do
c = read (priv->cancel_pipe[0], &buf, sizeof(buf));
while (c == -1 && errno == EINTR);
}
else
#endif
{
char ch;
do
c = read (priv->cancel_pipe[0], &ch, 1);
while (c == -1 && errno == EINTR);
}
}
priv->cancelled = FALSE;
}
@ -604,15 +658,9 @@ g_cancellable_cancel (GCancellable *cancellable)
if (priv->event)
SetEvent (priv->event);
#endif
if (priv->cancel_pipe[1] != -1)
{
const char ch = 'x';
gssize c;
do
c = write (priv->cancel_pipe[1], &ch, 1);
while (c == -1 && errno == EINTR);
}
g_cancellable_write_cancelled (cancellable);
G_UNLOCK(cancellable);
g_object_ref (cancellable);