mirror of https://github.com/torvalds/linux.git
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> |
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| .. | ||
| bitops | ||
| 4level-fixup.h | ||
| Kbuild | ||
| Kbuild.asm | ||
| atomic-long.h | ||
| atomic.h | ||
| atomic64.h | ||
| audit_change_attr.h | ||
| audit_dir_write.h | ||
| audit_read.h | ||
| audit_signal.h | ||
| audit_write.h | ||
| auxvec.h | ||
| bitops.h | ||
| bitsperlong.h | ||
| bug.h | ||
| bugs.h | ||
| cache.h | ||
| cacheflush.h | ||
| checksum.h | ||
| cmpxchg-local.h | ||
| cmpxchg.h | ||
| cputime.h | ||
| current.h | ||
| delay.h | ||
| device.h | ||
| div64.h | ||
| dma-coherent.h | ||
| dma-mapping-broken.h | ||
| dma-mapping-common.h | ||
| dma.h | ||
| emergency-restart.h | ||
| errno-base.h | ||
| errno.h | ||
| fb.h | ||
| fcntl.h | ||
| ftrace.h | ||
| futex.h | ||
| getorder.h | ||
| gpio.h | ||
| hardirq.h | ||
| hw_irq.h | ||
| ide_iops.h | ||
| int-l64.h | ||
| int-ll64.h | ||
| io-64-nonatomic-hi-lo.h | ||
| io-64-nonatomic-lo-hi.h | ||
| io.h | ||
| ioctl.h | ||
| ioctls.h | ||
| iomap.h | ||
| ipcbuf.h | ||
| irq.h | ||
| irq_regs.h | ||
| irqflags.h | ||
| kdebug.h | ||
| kmap_types.h | ||
| libata-portmap.h | ||
| linkage.h | ||
| local.h | ||
| local64.h | ||
| memory_model.h | ||
| mm_hooks.h | ||
| mman-common.h | ||
| mman.h | ||
| mmu.h | ||
| mmu_context.h | ||
| module.h | ||
| msgbuf.h | ||
| mutex-dec.h | ||
| mutex-null.h | ||
| mutex-xchg.h | ||
| mutex.h | ||
| page.h | ||
| param.h | ||
| parport.h | ||
| pci-bridge.h | ||
| pci-dma-compat.h | ||
| pci.h | ||
| pci_iomap.h | ||
| percpu.h | ||
| pgalloc.h | ||
| pgtable-nopmd.h | ||
| pgtable-nopud.h | ||
| pgtable.h | ||
| poll.h | ||
| posix_types.h | ||
| ptrace.h | ||
| resource.h | ||
| rtc.h | ||
| rwsem.h | ||
| scatterlist.h | ||
| sections.h | ||
| segment.h | ||
| sembuf.h | ||
| serial.h | ||
| setup.h | ||
| shmbuf.h | ||
| shmparam.h | ||
| siginfo.h | ||
| signal-defs.h | ||
| signal.h | ||
| sizes.h | ||
| socket.h | ||
| sockios.h | ||
| spinlock.h | ||
| stat.h | ||
| statfs.h | ||
| string.h | ||
| swab.h | ||
| syscall.h | ||
| syscalls.h | ||
| system.h | ||
| termbits.h | ||
| termios-base.h | ||
| termios.h | ||
| timex.h | ||
| tlb.h | ||
| tlbflush.h | ||
| topology.h | ||
| types.h | ||
| uaccess-unaligned.h | ||
| uaccess.h | ||
| ucontext.h | ||
| unaligned.h | ||
| unistd.h | ||
| user.h | ||
| vga.h | ||
| vmlinux.lds.h | ||
| xor.h | ||