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os: Delay freeing of epoll_wait return pointers until epoll is idle.

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Instead of freeing the struct ospollfd elements when the fd is
removed by the user, delay that until epoll is idle so that we are
sure no epoll_event structures could contain the stale pointer. This
handles cases where an fd is removed from the ospoll callback
interface, and also in case the OS keeps stale pointers around after
the call to epoll_ctl with EPOLL_CTL_DEL.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Keith Packard 2016-08-12 15:23:55 -07:00
parent 69b782aa75
commit 7d6fffb601
1 changed files with 23 additions and 2 deletions
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23
os/ospoll.c
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@ -54,6 +54,7 @@ struct ospollfd {
enum ospoll_trigger trigger;
void (*callback)(int fd, int xevents, void *data);
void *data;
struct xorg_list deleted;
};
struct ospoll {
@ -61,6 +62,7 @@ struct ospoll {
struct ospollfd **fds;
int num;
int size;
struct xorg_list deleted;
};
#endif
@ -115,6 +117,19 @@ ospoll_find(struct ospoll *ospoll, int fd)
return -(lo + 1);
}
#if EPOLL
static void
ospoll_clean_deleted(struct ospoll *ospoll)
{
struct ospollfd *osfd, *tmp;
xorg_list_for_each_entry_safe(osfd, tmp, &ospoll->deleted, deleted) {
xorg_list_del(&osfd->deleted);
free(osfd);
}
}
#endif
/* Insert an element into an array
*
* base: base address of array
@ -160,6 +175,7 @@ ospoll_create(void)
free (ospoll);
return NULL;
}
xorg_list_init(&ospoll->deleted);
return ospoll;
#endif
#if POLL
@ -174,6 +190,7 @@ ospoll_destroy(struct ospoll *ospoll)
if (ospoll) {
assert (ospoll->num == 0);
close(ospoll->epoll_fd);
ospoll_clean_deleted(ospoll);
free(ospoll->fds);
free(ospoll);
}
@ -291,7 +308,9 @@ ospoll_remove(struct ospoll *ospoll, int fd)
array_delete(ospoll->fds, ospoll->num, sizeof (ospoll->fds[0]), pos);
ospoll->num--;
free (osfd);
osfd->callback = NULL;
osfd->data = NULL;
xorg_list_add(&osfd->deleted, &ospoll->deleted);
#endif
#if POLL
array_delete(ospoll->fds, ospoll->num, sizeof (ospoll->fds[0]), pos);
@ -382,8 +401,10 @@ ospoll_wait(struct ospoll *ospoll, int timeout)
if (revents & (~(EPOLLIN|EPOLLOUT)))
xevents |= X_NOTIFY_ERROR;
if (osfd->callback)
osfd->callback(osfd->fd, xevents, osfd->data);
}
ospoll_clean_deleted(ospoll);
#endif
#if POLL
nready = xserver_poll(ospoll->fds, ospoll->num, timeout);