forked from Minki/linux
d80e731eca
This patch is intentionally incomplete to simplify the review. It ignores ep_unregister_pollwait() which plays with the same wqh. See the next change. epoll assumes that the EPOLL_CTL_ADD'ed file controls everything f_op->poll() needs. In particular it assumes that the wait queue can't go away until eventpoll_release(). This is not true in case of signalfd, the task which does EPOLL_CTL_ADD uses its ->sighand which is not connected to the file. This patch adds the special event, POLLFREE, currently only for epoll. It expects that init_poll_funcptr()'ed hook should do the necessary cleanup. Perhaps it should be defined as EPOLLFREE in eventpoll. __cleanup_sighand() is changed to do wake_up_poll(POLLFREE) if ->signalfd_wqh is not empty, we add the new signalfd_cleanup() helper. ep_poll_callback(POLLFREE) simply does list_del_init(task_list). This make this poll entry inconsistent, but we don't care. If you share epoll fd which contains our sigfd with another process you should blame yourself. signalfd is "really special". I simply do not know how we can define the "right" semantics if it used with epoll. The main problem is, epoll calls signalfd_poll() once to establish the connection with the wait queue, after that signalfd_poll(NULL) returns the different/inconsistent results depending on who does EPOLL_CTL_MOD/signalfd_read/etc. IOW: apart from sigmask, signalfd has nothing to do with the file, it works with the current thread. In short: this patch is the hack which tries to fix the symptoms. It also assumes that nobody can take tasklist_lock under epoll locks, this seems to be true. Note: - we do not have wake_up_all_poll() but wake_up_poll() is fine, poll/epoll doesn't use WQ_FLAG_EXCLUSIVE. - signalfd_cleanup() uses POLLHUP along with POLLFREE, we need a couple of simple changes in eventpoll.c to make sure it can't be "lost". Reported-by: Maxime Bizon <mbizon@freebox.fr> Cc: <stable@kernel.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
40 lines
764 B
C
40 lines
764 B
C
#ifndef __ASM_GENERIC_POLL_H
|
|
#define __ASM_GENERIC_POLL_H
|
|
|
|
/* These are specified by iBCS2 */
|
|
#define POLLIN 0x0001
|
|
#define POLLPRI 0x0002
|
|
#define POLLOUT 0x0004
|
|
#define POLLERR 0x0008
|
|
#define POLLHUP 0x0010
|
|
#define POLLNVAL 0x0020
|
|
|
|
/* The rest seem to be more-or-less nonstandard. Check them! */
|
|
#define POLLRDNORM 0x0040
|
|
#define POLLRDBAND 0x0080
|
|
#ifndef POLLWRNORM
|
|
#define POLLWRNORM 0x0100
|
|
#endif
|
|
#ifndef POLLWRBAND
|
|
#define POLLWRBAND 0x0200
|
|
#endif
|
|
#ifndef POLLMSG
|
|
#define POLLMSG 0x0400
|
|
#endif
|
|
#ifndef POLLREMOVE
|
|
#define POLLREMOVE 0x1000
|
|
#endif
|
|
#ifndef POLLRDHUP
|
|
#define POLLRDHUP 0x2000
|
|
#endif
|
|
|
|
#define POLLFREE 0x4000 /* currently only for epoll */
|
|
|
|
struct pollfd {
|
|
int fd;
|
|
short events;
|
|
short revents;
|
|
};
|
|
|
|
#endif /* __ASM_GENERIC_POLL_H */
|