Revision d80e731ecab420ddcb79ee9d0ac427acbc187b4b authored by Oleg Nesterov on 24 February 2012, 19:07:11 UTC, committed by Linus Torvalds on 24 February 2012, 19:42:50 UTC
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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File | Mode | Size |
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Kconfig | -rw-r--r-- | 12.4 KB |
Kconfig.debug | -rw-r--r-- | 1015 bytes |
Makefile | -rw-r--r-- | 1.8 KB |
backing-dev.c | -rw-r--r-- | 22.3 KB |
bootmem.c | -rw-r--r-- | 20.8 KB |
bounce.c | -rw-r--r-- | 6.5 KB |
cleancache.c | -rw-r--r-- | 6.9 KB |
compaction.c | -rw-r--r-- | 20.5 KB |
debug-pagealloc.c | -rw-r--r-- | 2.1 KB |
dmapool.c | -rw-r--r-- | 13.0 KB |
fadvise.c | -rw-r--r-- | 3.6 KB |
failslab.c | -rw-r--r-- | 1.3 KB |
filemap.c | -rw-r--r-- | 69.5 KB |
filemap_xip.c | -rw-r--r-- | 11.2 KB |
fremap.c | -rw-r--r-- | 6.7 KB |
highmem.c | -rw-r--r-- | 10.3 KB |
huge_memory.c | -rw-r--r-- | 63.6 KB |
hugetlb.c | -rw-r--r-- | 76.9 KB |
hwpoison-inject.c | -rw-r--r-- | 3.3 KB |
init-mm.c | -rw-r--r-- | 619 bytes |
internal.h | -rw-r--r-- | 8.6 KB |
kmemcheck.c | -rw-r--r-- | 2.8 KB |
kmemleak-test.c | -rw-r--r-- | 3.3 KB |
kmemleak.c | -rw-r--r-- | 52.6 KB |
ksm.c | -rw-r--r-- | 55.1 KB |
maccess.c | -rw-r--r-- | 1.6 KB |
madvise.c | -rw-r--r-- | 11.5 KB |
memblock.c | -rw-r--r-- | 26.6 KB |
memcontrol.c | -rw-r--r-- | 142.4 KB |
memory-failure.c | -rw-r--r-- | 41.7 KB |
memory.c | -rw-r--r-- | 107.6 KB |
memory_hotplug.c | -rw-r--r-- | 23.9 KB |
mempolicy.c | -rw-r--r-- | 64.5 KB |
mempool.c | -rw-r--r-- | 10.4 KB |
migrate.c | -rw-r--r-- | 33.6 KB |
mincore.c | -rw-r--r-- | 7.8 KB |
mlock.c | -rw-r--r-- | 15.7 KB |
mm_init.c | -rw-r--r-- | 3.7 KB |
mmap.c | -rw-r--r-- | 69.5 KB |
mmu_context.c | -rw-r--r-- | 1.4 KB |
mmu_notifier.c | -rw-r--r-- | 9.1 KB |
mmzone.c | -rw-r--r-- | 1.7 KB |
mprotect.c | -rw-r--r-- | 7.9 KB |
mremap.c | -rw-r--r-- | 14.0 KB |
msync.c | -rw-r--r-- | 2.4 KB |
nobootmem.c | -rw-r--r-- | 10.6 KB |
nommu.c | -rw-r--r-- | 51.0 KB |
oom_kill.c | -rw-r--r-- | 22.2 KB |
page-writeback.c | -rw-r--r-- | 67.3 KB |
page_alloc.c | -rw-r--r-- | 155.3 KB |
page_cgroup.c | -rw-r--r-- | 11.8 KB |
page_io.c | -rw-r--r-- | 3.2 KB |
page_isolation.c | -rw-r--r-- | 3.6 KB |
pagewalk.c | -rw-r--r-- | 5.7 KB |
percpu-km.c | -rw-r--r-- | 2.8 KB |
percpu-vm.c | -rw-r--r-- | 13.0 KB |
percpu.c | -rw-r--r-- | 56.6 KB |
pgtable-generic.c | -rw-r--r-- | 3.3 KB |
prio_tree.c | -rw-r--r-- | 6.3 KB |
process_vm_access.c | -rw-r--r-- | 13.3 KB |
quicklist.c | -rw-r--r-- | 2.4 KB |
readahead.c | -rw-r--r-- | 15.1 KB |
rmap.c | -rw-r--r-- | 52.2 KB |
shmem.c | -rw-r--r-- | 64.4 KB |
slab.c | -rw-r--r-- | 119.3 KB |
slob.c | -rw-r--r-- | 17.1 KB |
slub.c | -rw-r--r-- | 128.3 KB |
sparse-vmemmap.c | -rw-r--r-- | 5.9 KB |
sparse.c | -rw-r--r-- | 20.5 KB |
swap.c | -rw-r--r-- | 20.5 KB |
swap_state.c | -rw-r--r-- | 10.7 KB |
swapfile.c | -rw-r--r-- | 65.3 KB |
thrash.c | -rw-r--r-- | 3.9 KB |
truncate.c | -rw-r--r-- | 17.9 KB |
util.c | -rw-r--r-- | 7.3 KB |
vmalloc.c | -rw-r--r-- | 65.7 KB |
vmscan.c | -rw-r--r-- | 101.2 KB |
vmstat.c | -rw-r--r-- | 33.2 KB |
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