Oleg Nesterov d80e731eca epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree() ... 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>		2012-02-24 11:42:50 -08:00
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acpi
asm-generic	epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()	2012-02-24 11:42:50 -08:00
crypto
drm
keys
linux	epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()	2012-02-24 11:42:50 -08:00
math-emu
media
misc
mtd
net	netprio_cgroup: fix wrong memory access when NETPRIO_CGROUP=m	2012-02-10 15:08:57 -05:00
pcmcia
rdma
rxrpc
scsi
sound
target	target: Change target_submit_cmd() to return void	2012-02-07 06:41:04 +00:00
trace	writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue	2012-02-06 11:17:25 +08:00
video	fbdev fixes for 3.3	2012-02-07 15:54:02 -08:00
xen
Kbuild