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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
..
bitops asm-generic: add another generic ext2 atomic bitops 2011-07-26 16:49:46 -07:00
4level-fixup.h mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
Kbuild include: replace unifdef-y with header-y 2010-08-14 22:26:51 +02:00
Kbuild.asm include: replace unifdef-y with header-y 2010-08-14 22:26:51 +02:00
atomic-long.h asm-generic: merge branch 'master' of torvalds/linux-2.6 2009-06-12 11:32:58 +02:00
atomic.h asm-generic/atomic.h: allow SMP peeps to leverage this 2011-07-26 16:49:48 -07:00
atomic64.h lib: Provide generic atomic64_t implementation 2009-06-15 13:27:38 +10:00
audit_change_attr.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_dir_write.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_read.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_signal.h
…
audit_write.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
auxvec.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
bitops.h bitops: remove minix bitops from asm/bitops.h 2011-03-23 19:46:22 -07:00
bitsperlong.h asm-generic: introduce asm/bitsperlong.h 2009-06-11 21:02:14 +02:00
bug.h treewide: use __printf not __attribute__((format(printf,...))) 2011-10-31 17:30:54 -07:00
bugs.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
cache.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
cacheflush.h asm-generic/cacheflush.h: flush icache when copying to user pages 2011-05-25 08:39:37 -07:00
checksum.h Add extra arch overrides to asm-generic/checksum.h 2011-11-01 07:34:21 -07:00
cmpxchg-local.h Fix IRQ flag handling naming 2010-10-07 14:08:55 +01:00
cmpxchg.h
…
cputime.h Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 08:44:54 -08:00
current.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
delay.h asm-generic: delay.h fix udelay and ndelay for 8 bit args 2011-07-22 18:45:33 +02:00
device.h Driver Core: Add platform device arch data V3 2009-07-22 00:28:38 +02:00
div64.h
…
dma-coherent.h
…
dma-mapping-broken.h dma-mapping: remove dma_is_consistent API 2010-08-11 08:59:21 -07:00
dma-mapping-common.h dma-mapping: fix sync_single_range_* DMA debugging 2011-10-31 17:30:44 -07:00
dma.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
emergency-restart.h
…
errno-base.h
…
errno.h mm: make __get_user_pages return -EHWPOISON for HWPOISON page optionally 2011-03-17 13:08:27 -03:00
fb.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
fcntl.h locks: move F_INPROGRESS from fl_type to fl_flags field 2011-08-19 13:25:34 -04:00
ftrace.h asm-generic headers: add ftrace.h 2011-03-17 09:19:04 +08:00
futex.h futex: Sanitize futex ops argument types 2011-03-11 12:23:31 +01:00
getorder.h asm-generic: rename page.h and uaccess.h 2009-06-11 21:02:17 +02:00
gpio.h GPIO: add bindings for managed devices 2012-01-04 11:37:42 -07:00
hardirq.h Fix IRQ flag handling naming 2010-10-07 14:08:55 +01:00
hw_irq.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
ide_iops.h
…
int-l64.h asm-generic: introduce asm/bitsperlong.h 2009-06-11 21:02:14 +02:00
int-ll64.h asm-generic: introduce asm/bitsperlong.h 2009-06-11 21:02:14 +02:00
io-64-nonatomic-hi-lo.h asm-generic: architecture independent readq/writeq for 32bit environment 2012-02-21 16:47:28 -08:00
io-64-nonatomic-lo-hi.h asm-generic: architecture independent readq/writeq for 32bit environment 2012-02-21 16:47:28 -08:00
io.h lib: use generic pci_iomap on all architectures 2012-01-10 18:04:27 -08:00
ioctl.h
…
ioctls.h tty: add TIOCVHANGUP to allow clean tty shutdown of all ttys 2011-02-17 14:16:30 -08:00
iomap.h lib: add GENERIC_PCI_IOMAP 2011-11-28 21:12:42 +02:00
ipcbuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
irq.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
irq_regs.h core: Replace __get_cpu_var with __this_cpu_read if not used for an address. 2010-12-17 15:07:19 +01:00
irqflags.h Fix IRQ flag handling naming 2010-10-07 14:08:55 +01:00
kdebug.h asm-generic: kdebug.h: Checkpatch cleanup 2010-10-09 21:51:44 +02:00
kmap_types.h include/asm-generic/kmap_types.h: add helpful reminder 2010-05-25 08:07:03 -07:00
libata-portmap.h
…
linkage.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
local.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
local64.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
memory_model.h mm: fix __page_to_pfn for a const struct page argument 2011-08-17 13:00:20 -07:00
mm_hooks.h
…
mman-common.h thp: mm: define MADV_NOHUGEPAGE 2011-01-13 17:32:47 -08:00
mman.h mm: add MAP_HUGETLB for mmaping pseudo-anonymous huge page regions 2009-09-22 07:17:41 -07:00
mmu.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
mmu_context.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
module.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
msgbuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
mutex-dec.h mutex: speed up generic mutex implementations 2008-10-23 09:18:20 -07:00
mutex-null.h
…
mutex-xchg.h mutex: speed up generic mutex implementations 2008-10-23 09:18:20 -07:00
mutex.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
page.h The following changes since commit 3ee72ca992 2012-01-10 17:39:40 -08:00
param.h UAPI: Rearrange definition of HZ in asm-generic/param.h 2011-12-13 09:26:45 +00:00
parport.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
pci-bridge.h pci: move microblaze and powerpc pci flag functions into asm-generic 2011-07-12 11:13:07 -05:00
pci-dma-compat.h dma-mapping: pci: move pci_set_dma_mask and pci_set_consistent_dma_mask to pci-dma-compat.h 2010-03-12 15:52:42 -08:00
pci.h PCI: remove pcibios_scan_all_fns() 2009-09-09 13:29:18 -07:00
pci_iomap.h lib: add NO_GENERIC_PCI_IOPORT_MAP 2012-01-31 23:19:47 +02:00
percpu.h percpu: Optimize __get_cpu_var() 2010-09-10 10:56:51 +02:00
pgalloc.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
pgtable-nopmd.h mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
pgtable-nopud.h mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
pgtable.h include/asm-generic/pgtable.h: fix unbalanced parenthesis 2011-06-15 20:04:00 -07:00
poll.h epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree() 2012-02-24 11:42:50 -08:00
posix_types.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
ptrace.h asm-generic/ptrace.h: start a common low level ptrace helper 2011-05-26 17:12:36 -07:00
resource.h ulimit: raise default hard ulimit on number of files to 4096 2011-05-25 08:39:43 -07:00
rtc.h asm-generic: make get_rtc_time overridable 2009-06-11 21:02:18 +02:00
rwsem.h Hexagon: Add locking types and functions 2011-11-01 07:34:20 -07:00
scatterlist.h asm-generic: remove ARCH_HAS_SG_CHAIN in scatterlist.h 2010-05-27 09:12:54 -07:00
sections.h x86: Separate out entry text section 2011-03-08 17:22:11 +01:00
segment.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
sembuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
serial.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
setup.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
shmbuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
shmparam.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
siginfo.h Fix common misspellings 2011-03-31 11:26:23 -03:00
signal-defs.h asm-generic: rename termios.h, signal.h and mman.h 2009-06-11 21:01:52 +02:00
signal.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
sizes.h asm-generic headers: add sizes.h 2011-03-17 09:19:04 +08:00
socket.h net: add wireless TX status socket option 2011-11-09 16:01:02 -05:00
sockios.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
spinlock.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
stat.h asm-generic/stat.h: support 64-bit file time_t for stat() 2010-11-01 15:31:29 -04:00
statfs.h add f_flags to struct statfs(64) 2010-08-09 16:48:44 -04:00
string.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
swab.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
syscall.h asm-generic: syscall_get_nr returns int 2009-09-22 19:56:50 -07:00
syscalls.h Fix the declaration of sys_execve() in asm-generic/syscalls.h 2010-08-18 12:12:38 -07:00
system.h asm-generic/system.h: drop useless __KERNEL__ 2011-07-25 20:57:14 -07:00
termbits.h tty: Add EXTPROC support for LINEMODE 2010-08-10 13:47:39 -07:00
termios-base.h asm-generic: rename termios.h, signal.h and mman.h 2009-06-11 21:01:52 +02:00
termios.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
timex.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
tlb.h thp: add tlb_remove_pmd_tlb_entry 2012-01-12 20:13:08 -08:00
tlbflush.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
topology.h topology: alternate fix for ia64 tiger_defconfig build breakage 2010-08-09 20:44:57 -07:00
types.h consolidate umode_t declarations 2012-01-03 22:55:17 -05:00
uaccess-unaligned.h asm-generic: rename page.h and uaccess.h 2009-06-11 21:02:17 +02:00
uaccess.h fix default __strnlen_user macro 2011-10-06 19:47:12 -04:00
ucontext.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
unaligned.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
unistd.h asm-generic/unistd.h: support new process_vm_{readv,write} syscalls 2011-12-03 15:31:48 -05:00
user.h asm-generic/user.h: Fix spelling in comment 2011-03-01 15:49:39 +01:00
vga.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
vmlinux.lds.h m68k: Finally remove leftover markers sections 2011-10-24 21:00:34 +02:00
xor.h sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00