Jason Baron 4ff36ee94d epoll: do not take the nested ep->mtx on EPOLL_CTL_DEL ... The EPOLL_CTL_DEL path of epoll contains a classic, ab-ba deadlock. That is, epoll_ctl(a, EPOLL_CTL_DEL, b, x), will deadlock with epoll_ctl(b, EPOLL_CTL_DEL, a, x). The deadlock was introduced with commmit 67347fe4e6 ("epoll: do not take global 'epmutex' for simple topologies"). The acquistion of the ep->mtx for the destination 'ep' was added such that a concurrent EPOLL_CTL_ADD operation would see the correct state of the ep (Specifically, the check for '!list_empty(&f.file->f_ep_links') However, by simply not acquiring the lock, we do not serialize behind the ep->mtx from the add path, and thus may perform a full path check when if we had waited a little longer it may not have been necessary. However, this is a transient state, and performing the full loop checking in this case is not harmful. The important point is that we wouldn't miss doing the full loop checking when required, since EPOLL_CTL_ADD always locks any 'ep's that its operating upon. The reason we don't need to do lock ordering in the add path, is that we are already are holding the global 'epmutex' whenever we do the double lock. Further, the original posting of this patch, which was tested for the intended performance gains, did not perform this additional locking. Signed-off-by: Jason Baron <jbaron@akamai.com> Cc: Nathan Zimmer <nzimmer@sgi.com> Cc: Eric Wong <normalperson@yhbt.net> Cc: Nelson Elhage <nelhage@nelhage.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2014-01-02 14:40:30 -08:00
..
9p	consolidate simple ->d_delete() instances	2013-11-15 22:04:17 -05:00
adfs	adfs: delayed freeing of sbi	2013-10-24 23:43:27 -04:00
affs	remove obsolete references to powertweak	2013-11-27 20:34:32 -08:00
afs	Merge branch 'fscache' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs into linux-next	2013-10-28 19:36:46 -04:00
autofs4	autofs4: make freeing sbi rcu-delayed	2013-10-24 23:43:27 -04:00
befs	befs: split symlink iops in two - for short and long symlinks resp.	2013-10-24 23:34:50 -04:00
bfs	truncate: drop 'oldsize' truncate_pagecache() parameter	2013-09-12 15:38:02 -07:00
btrfs	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs	2013-12-12 15:25:10 -08:00
cachefiles	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-11-13 15:34:18 +09:00
ceph	ceph: Avoid data inconsistency due to d-cache aliasing in readpage()	2013-12-13 09:11:38 -08:00
cifs	cifs: set FILE_CREATED	2013-12-27 15:14:45 -06:00
coda	coda_revalidate_inode(): switch to passing inode...	2013-11-09 00:16:21 -05:00
configfs	configfs: fix race between dentry put and lookup	2013-11-21 16:42:27 -08:00
cramfs	cramfs: mark as obsolete	2013-11-13 12:09:12 +09:00
debugfs	debugfs: use list_next_entry() in debugfs_remove_recursive()	2013-11-13 12:09:24 +09:00
devpts	devpts: plug the memory leak in kill_sb	2013-11-13 12:09:36 +09:00
dlm	genetlink: only pass array to genl_register_family_with_ops()	2013-11-19 16:39:05 -05:00
ecryptfs	Quiet static checkers by removing unneeded conditionals	2013-11-22 10:58:14 -08:00
efivarfs	consolidate simple ->d_delete() instances	2013-11-15 22:04:17 -05:00
efs	efs: iget_locked() doesn't return an ERR_PTR()	2013-08-24 12:10:22 -04:00
exofs	truncate: drop 'oldsize' truncate_pagecache() parameter	2013-09-12 15:38:02 -07:00
exportfs	exportfs: fix quadratic behavior in filehandle lookup	2013-11-09 00:16:38 -05:00
ext2	ext2: Fix oops in ext2_get_block() called from ext2_quota_write()	2013-12-04 12:26:51 +01:00
ext3	Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs	2013-11-13 15:25:47 +09:00
ext4	ext4: add explicit casts when masking cluster sizes	2013-12-20 09:29:35 -05:00
f2fs	f2fs: issue more large discard command	2013-11-11 09:36:32 +09:00
fat	fat: rcu-delay unloading nls and freeing sbi	2013-10-24 23:43:28 -04:00
freevxfs	[readdir] convert freevxfs	2013-06-29 12:56:53 +04:00
fscache	Merge branch 'for-3.13/core' of git://git.kernel.dk/linux-block	2013-11-14 12:08:14 +09:00
fuse	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-11-13 15:34:18 +09:00
gfs2	GFS2: Fix ref count bug relating to atomic_open	2013-11-21 18:47:57 +00:00
hfs	fs/hfs/btree.h: remove duplicate defines	2013-11-13 12:09:32 +09:00
hfsplus	block: submit_bio_wait() conversions	2013-11-24 16:33:41 -07:00
hostfs	consolidate simple ->d_delete() instances	2013-11-15 22:04:17 -05:00
hpfs	locks: break delegations on any attribute modification	2013-11-09 00:16:44 -05:00
hppfs	clean up scary strncpy(dst, src, strlen(src)) uses	2013-07-03 16:07:41 -07:00
hugetlbfs	cope with potentially long ->d_dname() output for shmem/hugetlb	2013-08-24 12:10:17 -04:00
isofs	isofs: don't pass dentry to isofs_hash{i,}_common()	2013-10-24 23:34:59 -04:00
jbd	jbd: Revert "jbd: remove dependency on __GFP_NOFAIL"	2013-10-31 20:37:15 +01:00
jbd2	jbd2: rename obsoleted msg JBD->JBD2	2013-12-08 21:14:59 -05:00
jffs2	jffs2: do not support the MLC nand	2013-10-27 16:27:07 -07:00
jfs	Just a patch to fix an oops in an error path.	2013-10-22 09:01:11 +01:00
lockd	LOCKD: Don't call utsname()->nodename from nlmclnt_setlockargs	2013-08-05 15:03:46 -04:00
logfs	block: submit_bio_wait() conversions	2013-11-24 16:33:41 -07:00
minix	fs/minix: Drop dependency on H8300	2013-09-16 18:20:25 -07:00
ncpfs	ncpfs: rcu-delay unload_nls() and freeing ncp_server	2013-10-24 23:43:28 -04:00
nfs	NFS client bugfixes	2013-12-05 13:05:48 -08:00
nfs_common
nfsd	nfsd: when reusing an existing repcache entry, unhash it first	2013-12-10 20:34:44 -05:00
nilfs2	nilfs2: fix issue with race condition of competition between segments for dirty blocks	2013-09-30 14:31:02 -07:00
nls
notify	fsnotify: update comments concerning locking scheme	2013-07-09 10:33:20 -07:00
ntfs	iget/iget5: don't bother with ->i_lock until we find a match	2013-11-09 00:16:31 -05:00
ocfs2	tree-wide: use reinit_completion instead of INIT_COMPLETION	2013-11-15 09:32:21 +09:00
omfs	truncate: drop 'oldsize' truncate_pagecache() parameter	2013-09-12 15:38:02 -07:00
openpromfs	[readdir] convert openpromfs	2013-06-29 12:56:32 +04:00
proc	procfs: also fix proc_reg_get_unmapped_area() for !MMU case	2013-12-12 18:19:26 -08:00
pstore	pstore: Don't allow high traffic options on fragile devices	2013-12-20 13:12:01 -08:00
qnx4	qnx4: i_sb is never NULL	2013-11-09 00:16:32 -05:00
qnx6	[readdir] convert qnx6	2013-06-29 12:56:39 +04:00
quota	genetlink: make multicast groups const, prevent abuse	2013-11-19 16:39:06 -05:00
ramfs	initmpfs: move rootfs code from fs/ramfs/ to init/	2013-09-11 15:59:37 -07:00
reiserfs	reiserfs: fix race with flush_used_journal_lists and flush_journal_list	2013-09-24 11:24:21 +02:00
romfs	[readdir] convert romfs	2013-06-29 12:56:29 +04:00
squashfs	Squashfs: fix failure to unlock pages on decompress error	2013-11-24 01:02:50 +00:00
sysfs	sysfs: give different locking key to regular and bin files	2013-12-07 21:22:00 -08:00
sysv	sysv: Add forgotten superblock lock init for v7 fs	2013-09-29 22:02:02 -04:00
ubifs	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-11-13 15:34:18 +09:00
udf	udf: fix for pathetic mount times in case of invalid file system	2013-10-18 22:39:07 +02:00
ufs	truncate: drop 'oldsize' truncate_pagecache() parameter	2013-09-12 15:38:02 -07:00
xfs	xfs: abort metadata writeback on permanent errors	2013-12-17 09:40:23 -06:00
aio.c	Merge git://git.kvack.org/~bcrl/aio-next	2013-12-22 11:03:49 -08:00
anon_inodes.c	... and kill anon_inode_getfile_private()	2013-11-09 00:16:28 -05:00
attr.c	locks: break delegations on any attribute modification	2013-11-09 00:16:44 -05:00
bad_inode.c	[readdir] ->readdir() is gone	2013-06-29 12:57:04 +04:00
binfmt_aout.c	dump_skip(): dump_seek() replacement taking coredump_params	2013-11-09 00:16:26 -05:00
binfmt_elf_fdpic.c	elf{,_fdpic} coredump: get rid of pointless if (siginfo->si_signo)	2013-11-09 00:16:30 -05:00
binfmt_elf.c	elf{,_fdpic} coredump: get rid of pointless if (siginfo->si_signo)	2013-11-09 00:16:30 -05:00
binfmt_em86.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
binfmt_flat.c
binfmt_misc.c
binfmt_script.c
binfmt_som.c
bio-integrity.c	Merge branch 'for-3.12/core' of git://git.kernel.dk/linux-block	2013-09-22 15:00:11 -07:00
bio.c	bio: fix argument of __bio_add_page() for max_sectors > 0xffff	2013-11-18 12:31:27 -07:00
block_dev.c	a trivial writeback fix	2013-09-13 23:06:40 -04:00
buffer.c	fs: buffer: move allocation failure loop into the allocator	2013-10-16 21:35:53 -07:00
char_dev.c	Merge branch 'for-3.13/core' of git://git.kernel.dk/linux-block	2013-11-14 12:08:14 +09:00
compat_binfmt_elf.c
compat_ioctl.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
compat.c	[readdir] constify ->actor	2013-06-29 12:57:05 +04:00
coredump.c	dump_emit(): use __kernel_write(), not vfs_write()	2013-11-15 22:04:09 -05:00
coredump.h
dcache.c	dcache: allow word-at-a-time name hashing with big-endian CPUs	2013-12-12 10:39:01 -08:00
dcookies.c
direct-io.c	direct-io: Use return from cmpxchg to decide of assignment happened	2013-09-09 10:47:42 -07:00
drop_caches.c	shrinker: add node awareness	2013-09-10 18:56:31 -04:00
eventfd.c
eventpoll.c	epoll: do not take the nested ep->mtx on EPOLL_CTL_DEL	2014-01-02 14:40:30 -08:00
exec.c	Merge git://git.infradead.org/users/eparis/audit	2013-11-21 19:18:14 -08:00
fcntl.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
fhandle.c
file_table.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-11-13 15:34:18 +09:00
file.c
filesystems.c
fs_struct.c	seqcount: Add lockdep functionality to seqcount/seqlock structures	2013-11-06 12:40:26 +01:00
fs-writeback.c	Merge branch 'akpm' (patches from Andrew Morton)	2013-11-13 15:45:43 +09:00
generic_acl.c
inode.c	locks: break delegations on any attribute modification	2013-11-09 00:16:44 -05:00
internal.h	get rid of s_files and files_lock	2013-11-09 00:16:20 -05:00
ioctl.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
ioprio.c
Kconfig
Kconfig.binfmt
libfs.c	consolidate simple ->d_delete() instances	2013-11-15 22:04:17 -05:00
locks.c	locks: missing unlock on error in generic_add_lease()	2013-11-13 07:30:53 -05:00
Makefile
mbcache.c	fs: convert fs shrinkers to new scan/count API	2013-09-10 18:56:31 -04:00
mount.h	RCU'd vfsmounts	2013-11-09 00:16:19 -05:00
mpage.c
namei.c	dcache: allow word-at-a-time name hashing with big-endian CPUs	2013-12-12 10:39:01 -08:00
namespace.c	RCU'd vfsmounts	2013-11-09 00:16:19 -05:00
no-block.c
open.c	locks: break delegations on any attribute modification	2013-11-09 00:16:44 -05:00
pipe.c	vfs: fix subtle use-after-free of pipe_inode_info	2013-12-02 09:44:51 -08:00
pnode.c	split __lookup_mnt() in two functions	2013-10-24 23:35:00 -04:00
pnode.h	vfs: Don't copy mount bind mounts of /proc/<pid>/ns/mnt between namespaces	2013-08-26 18:42:15 -07:00
posix_acl.c
proc_namespace.c	don't bother with vfsmount_lock in mounts_poll()	2013-10-24 23:34:59 -04:00
read_write.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
readdir.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
select.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-11-13 15:34:18 +09:00
seq_file.c	seq_file: always clear m->count when we free m->buf	2013-11-18 19:07:53 -08:00
signalfd.c
splice.c	file->f_op is never NULL...	2013-10-24 23:34:54 -04:00
stack.c
stat.c	vfs: split out vfs_getattr_nosec	2013-11-09 00:16:31 -05:00
statfs.c	vfs: allow O_PATH file descriptors for fstatfs()	2013-10-12 13:12:31 -07:00
super.c	get rid of s_files and files_lock	2013-11-09 00:16:20 -05:00
sync.c	Merge branch 'akpm' (patches from Andrew Morton)	2013-11-13 15:45:43 +09:00
timerfd.c
utimes.c	locks: break delegations on any attribute modification	2013-11-09 00:16:44 -05:00
xattr_acl.c
xattr.c