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Davide Libenzi 3419b23a91 [PATCH] epoll: use unlocked wqueue operations 
A few days ago Arjan signaled a lockdep red flag on epoll locks, and
precisely between the epoll's device structure lock (->lock) and the wait
queue head lock (->lock).

Like I explained in another email, and directly to Arjan, this can't happen
in reality because of the explicit check at eventpoll.c:592, that does not
allow to drop an epoll fd inside the same epoll fd.  Since lockdep is
working on per-structure locks, it will never be able to know of policies
enforced in other parts of the code.

It was decided time ago of having the ability to drop epoll fds inside
other epoll fds, that triggers a very trick wakeup operations (due to
possibly reentrant callback-driven wakeups) handled by the
ep_poll_safewake() function.  While looking again at the code though, I
noticed that all the operations done on the epoll's main structure wait
queue head (->wq) are already protected by the epoll lock (->lock), so that
locked-style functions can be used to manipulate the ->wq member.  This
makes both a lock-acquire save, and lockdep happy.

Running totalmess on my dual opteron for a while did not reveal any problem
so far:

http://www.xmailserver.org/totalmess.c

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-25 10:01:13 -07:00
..
9p [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
adfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
affs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
afs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
autofs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
autofs4 [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
befs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
bfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
cifs [PATCH] vfs: add lock owner argument to flush operation 2006-06-23 07:43:02 -07:00
coda [PATCH] vfs: add lock owner argument to flush operation 2006-06-23 07:43:02 -07:00
configfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
cramfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
debugfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
devfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
devpts [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
efs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
exportfs
ext2 [PATCH] Make EXT2_DEBUG work again 2006-06-25 10:01:12 -07:00
ext3 [PATCH] ext3_fsblk_t: the rest of in-kernel filesystem blocks conversion 2006-06-25 10:01:10 -07:00
fat [PATCH] fs/fat/misc.c: unexport fat_sync_bhs 2006-06-23 07:43:03 -07:00
freevxfs [PATCH] fs/freevxfs: cleanup of spelling errors 2006-06-25 10:01:01 -07:00
fuse [PATCH] vfs: add lock owner argument to flush operation 2006-06-23 07:43:02 -07:00
hfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
hfsplus [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
hostfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
hpfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
hppfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
hugetlbfs [PATCH] tightening hugetlb strict accounting 2006-06-23 07:42:48 -07:00
isofs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
jbd [PATCH] ext3: fix memory leak when the journal file is corrupted 2006-06-25 10:01:07 -07:00
jffs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
jffs2 [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
jfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
lockd
minix [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
msdos [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
ncpfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
nfs [PATCH] vfs: add lock owner argument to flush operation 2006-06-23 07:43:02 -07:00
nfs_common
nfsd [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
nls
ntfs [PATCH] Prepare for __copy_from_user_inatomic to not zero missed bytes 2006-06-25 10:01:09 -07:00
ocfs2 [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
openpromfs [PATCH] openpromfs: factorize out 2006-06-25 10:01:05 -07:00
partitions [PATCH] make kernel warn about incorrectly sized partitions 2006-06-23 07:43:09 -07:00
proc [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
qnx4 [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
ramfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
reiserfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
romfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
smbfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
sysfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
sysv [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
udf [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
ufs [PATCH] fs/ufs/inode.c: make 2 functions static 2006-06-25 10:01:04 -07:00
vfat [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
xfs [PATCH] for_each_possible_cpu: xfs 2006-06-23 07:42:45 -07:00
aio.c [PATCH] list: use list_replace_init() instead of list_splice_init() 2006-06-23 07:43:07 -07:00
attr.c
bad_inode.c
binfmt_aout.c
binfmt_elf.c [PATCH] binflt_elf: remove more casts 2006-06-23 07:43:05 -07:00
binfmt_elf_fdpic.c [PATCH] frv: binfmt_elf_fdpic __user annotations 2006-06-23 07:42:54 -07:00
binfmt_em86.c
binfmt_flat.c
binfmt_misc.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
binfmt_script.c
binfmt_som.c
bio.c
block_dev.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
buffer.c [PATCH] Kill PF_SYNCWRITE flag 2006-06-23 17:10:39 +02:00
char_dev.c
compat.c [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
compat_ioctl.c
dcache.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
dcookies.c
direct-io.c [PATCH] Kill PF_SYNCWRITE flag 2006-06-23 17:10:39 +02:00
dnotify.c
dquot.c
drop_caches.c
eventpoll.c [PATCH] epoll: use unlocked wqueue operations 2006-06-25 10:01:13 -07:00
exec.c [PATCH] remove steal_locks() 2006-06-22 15:05:57 -07:00
fcntl.c
fifo.c
file.c
file_table.c [PATCH] percpu counter data type changes to suppport more than 2**31 ext3 free blocks counter 2006-06-23 07:43:06 -07:00
filesystems.c
fs-writeback.c [PATCH] Kill PF_SYNCWRITE flag 2006-06-23 17:10:39 +02:00
inode.c
inotify.c
inotify_user.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
ioctl.c
ioprio.c [PATCH] lsm: add task_setioprio hook 2006-06-23 07:42:53 -07:00
Kconfig [PATCH] Make procfs obligatory except under CONFIG_EMBEDDED 2006-06-25 10:01:11 -07:00
Kconfig.binfmt
libfs.c [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
locks.c [PATCH] fs/locks.c: make posix_locks_deadlock() static 2006-06-23 07:43:03 -07:00
Makefile
mbcache.c
mpage.c [PATCH] writeback: fix range handling 2006-06-23 07:42:49 -07:00
namei.c [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
namespace.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
nfsctl.c
open.c [PATCH] vfs: add lock owner argument to flush operation 2006-06-23 07:43:02 -07:00
pipe.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
pnode.c
pnode.h
posix_acl.c
quota.c
quota_v1.c
quota_v2.c
read_write.c
readdir.c
select.c [PATCH] Poll cleanups/microoptimizations 2006-06-23 07:43:03 -07:00
seq_file.c
splice.c [PATCH] splice: retrieve mapping after locking the page 2006-06-23 17:10:39 +02:00
stat.c
super.c [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
sync.c [PATCH] writeback: fix range handling 2006-06-23 07:42:49 -07:00
xattr.c
xattr_acl.c