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e22553e2a2
linux/fs
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Chris Mason e22553e2a2 eventfd: don't take the spinlock in eventfd_poll 
The spinlock in eventfd_poll is trying to protect the count of events so
it can decide if it should return POLLIN, POLLERR, or POLLOUT.  But,
because of the way we drop the lock after calling poll_wait, and drop it
again before returning, we have the same pile of races with the lock as
we do with a single read of ctx->count().

This replaces the lock with a read barrier and single read.

eventfd_write does a single bump of ctx->count, so this should not add
new races with adding events.  eventfd_read is similar, it will do a
single decrement with the lock held, and so we're making the race with
concurrent readers slightly larger.

This spinlock is the top CPU user in kernel code during one of our
workloads.  Removing it gives us a ~2% boost.

[arnd@arndb.de: avoid unused variable warning]
[dan.carpenter@oracle.com: type bug in eventfd_poll()]
Signed-off-by: Chris Mason <clm@fb.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-17 14:34:52 -08:00
..
9p Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
adfs
affs fs/affs/file.c: remove obsolete pagesize check 2014-12-13 12:42:52 -08:00
afs Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
autofs4 assorted conversions to %p[dD] 2014-11-19 13:01:20 -05:00
befs fs/befs/linuxvfs.c: remove unnecessary casting 2015-02-17 14:34:50 -08:00
bfs
btrfs Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
cachefiles assorted conversions to %p[dD] 2014-11-19 13:01:20 -05:00
ceph Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
cifs Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
coda fs/coda/dir.c: forward declaration clean-up 2015-02-17 14:34:50 -08:00
configfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
cramfs
debugfs Driver core patches for 3.19-rc1 2014-12-14 16:10:09 -08:00
devpts
dlm netlink: make nlmsg_end() and genlmsg_end() void 2015-01-18 01:03:45 -05:00
ecryptfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
efivarfs * Move efivarfs from the misc filesystem section to pseudo filesystem, 2015-01-29 19:16:40 +01:00
efs
exofs vfs: remove get_xip_mem 2015-02-16 17:56:03 -08:00
exportfs move d_rcu from overlapping d_child to overlapping d_alias 2014-11-03 15:20:29 -05:00
ext2 ext2: get rid of most mentions of XIP in ext2 2015-02-16 17:56:04 -08:00
ext3 ext3: destroy sbi mutexes in put_super 2015-01-05 11:13:55 +01:00
ext4 ext4: add DAX functionality 2015-02-16 17:56:04 -08:00
f2fs Merge tag 'for-f2fs-3.20' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs 2015-02-12 19:28:50 -08:00
fat fs: fat: use MSDOS_SB macro to get msdos_sb_info 2015-02-17 14:34:51 -08:00
freevxfs
fscache fs/fscache/object-list.c: use __seq_open_private() 2014-10-13 17:52:21 +01:00
fuse Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
gfs2 Merge branch 'akpm' (patches from Andrew) 2015-02-12 18:54:28 -08:00
hfs fs/hfs/catalog.c: fix comparison bug in hfs_cat_keycmp 2014-12-10 17:41:16 -08:00
hfsplus hfsplus: fix longname handling 2014-12-18 19:08:10 -08:00
hostfs
hpfs
hppfs vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
hugetlbfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
isofs isofs: Fix bug in the way to check if the year is a leap year 2015-01-07 09:51:49 +01:00
jbd jbd: Deletion of an unnecessary check before the function call "iput" 2014-11-18 10:15:29 +01:00
jbd2 Lots of bugs fixes, including Zheng and Jan's extent status shrinker 2014-12-12 09:28:03 -08:00
jffs2 jffs2: Drop bogus if in comment 2014-11-28 18:23:44 -08:00
jfs jfs: Deletion of an unnecessary check before the function call "unload_nls" 2015-02-02 15:02:34 -06:00
kernfs kernfs: remove KERNFS_STATIC_NAME 2015-02-13 21:21:36 -08:00
lockd Merge branch 'for-3.20' of git://linux-nfs.org/~bfields/linux 2015-02-12 10:39:41 -08:00
logfs
minix
ncpfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
nfs Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
nfs_common lockd: move lockd's grace period handling into its own module 2014-09-17 16:33:11 -04:00
nfsd nfsd: default NFSv4.2 to on 2015-02-09 14:58:50 -05:00
nilfs2 Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
nls
notify fanotify: don't set FAN_ONDIR implicitly on a marks ignored mask 2015-02-10 14:30:28 -08:00
ntfs fs: export inode_to_bdi and use it in favor of mapping->backing_dev_info 2015-01-20 14:03:04 -07:00
ocfs2 ocfs2: set append dio as a ro compat feature 2015-02-16 17:56:05 -08:00
omfs FS/OMFS: block number sanity check during fill_super operation 2014-10-14 02:18:22 +02:00
openpromfs
overlayfs Merge branch 'iov_iter' into for-next 2014-12-08 20:39:29 -05:00
proc vmcore: fix PT_NOTE n_namesz, n_descsz overflow issue 2015-02-17 14:34:52 -08:00
pstore pstore: Fix sprintf format specifier in pstore_dump() 2015-01-16 16:01:29 -08:00
qnx4
qnx6
quota Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2015-02-10 15:52:38 -08:00
ramfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
reiserfs fs/reiserfs/inode.c: replace 0 by NULL for pointers 2015-02-17 14:34:51 -08:00
romfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
squashfs Squashfs: Add LZ4 compression configuration option 2014-11-27 18:48:44 +00:00
sysfs driver core patches for 3.20-rc1 2015-02-15 11:11:47 -08:00
sysv
ubifs Merge branch 'for-linus-v3.20' of git://git.infradead.org/linux-ubifs 2015-02-15 10:11:39 -08:00
udf udf: remove bool assignment to 0/1 2015-02-05 16:34:25 +01:00
ufs fs/ufs/super.c: fix potential race condition 2015-02-17 14:34:51 -08:00
xfs Merge branch 'akpm' (patches from Andrew) 2015-02-12 18:54:28 -08:00
aio.c Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
anon_inodes.c
attr.c
bad_inode.c
binfmt_aout.c assorted conversions to %p[dD] 2014-11-19 13:01:20 -05:00
binfmt_elf_fdpic.c handle suicide on late failure exits in execve() in search_binary_handler() 2014-10-09 02:39:00 -04:00
binfmt_elf.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-12-11 17:56:37 -08:00
binfmt_em86.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
binfmt_flat.c
binfmt_misc.c unfuck binfmt_misc.c (broken by commit e6084d4) 2014-12-17 08:27:14 -05:00
binfmt_script.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
binfmt_som.c
block_dev.c Merge branch 'for-3.20/core' of git://git.kernel.dk/linux-block 2015-02-12 14:13:23 -08:00
buffer.c fs: clarify rate limit suppressed buffer I/O errors 2014-10-21 13:55:11 -06:00
char_dev.c fs: introduce f_op->mmap_capabilities for nommu mmap support 2015-01-20 14:02:58 -07:00
compat_binfmt_elf.c
compat_ioctl.c
compat.c vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
coredump.c coredump: add %i/%I in core_pattern to report the tid of the crashed thread 2014-10-14 02:18:21 +02:00
dax.c dax: add dax_zero_page_range 2015-02-16 17:56:04 -08:00
dcache.c fs: dcache: manually unpoison dname after allocation to shut up kasan's reports 2015-02-13 21:21:41 -08:00
dcookies.c
direct-io.c fuse: honour max_read and max_write in direct_io mode 2014-09-26 21:16:51 -04:00
drop_caches.c vmscan: per memory cgroup slab shrinkers 2015-02-12 18:54:09 -08:00
eventfd.c eventfd: don't take the spinlock in eventfd_poll 2015-02-17 14:34:52 -08:00
eventpoll.c epoll: optimize setting task running after blocking 2015-02-13 21:21:40 -08:00
exec.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
fcntl.c vfs: renumber FMODE_NONOTIFY and add to uniqueness check 2015-01-08 15:10:52 -08:00
fhandle.c
file_table.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-10-13 11:28:42 +02:00
file.c fs/file.c: replace get_unused_fd() with get_unused_fd_flags(0) 2014-12-10 17:41:10 -08:00
filesystems.c
fs_pin.c
fs_struct.c
fs-writeback.c fs: make inode_to_bdi() handle NULL inode 2015-01-22 08:13:17 -07:00
inode.c Merge branch 'akpm' (patches from Andrew) 2015-02-12 18:54:28 -08:00
internal.h list_lru: introduce list_lru_shrink_{count,walk} 2015-02-12 18:54:08 -08:00
ioctl.c fsioctl.c: make generic_block_fiemap() signal-tolerant 2015-02-10 14:30:30 -08:00
Kconfig dax: does not work correctly with virtual aliasing caches 2015-02-16 17:56:04 -08:00
Kconfig.binfmt binfmt_elf: allow arch code to examine PT_LOPROC ... PT_HIPROC headers 2014-11-24 07:45:02 +01:00
libfs.c move d_rcu from overlapping d_child to overlapping d_alias 2014-11-03 15:20:29 -05:00
locks.c fs: add FL_LAYOUT lease type 2015-02-02 18:09:38 +01:00
Makefile vfs,ext2: remove CONFIG_EXT2_FS_XIP and rename CONFIG_FS_XIP to CONFIG_FS_DAX 2015-02-16 17:56:04 -08:00
mbcache.c
mount.h common object embedded into various struct ....ns 2014-12-04 14:31:00 -05:00
mpage.c vfs: guard end of device for mpage interface 2014-10-09 22:25:53 -04:00
namei.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-12-16 15:53:03 -08:00
namespace.c fs/namespace: convert devname allocation to kstrdup_const 2015-02-13 21:21:36 -08:00
no-block.c
nsfs.c take the targets of /proc/*/ns/* symlinks to separate fs 2014-12-10 21:30:20 -05:00
open.c vfs: remove get_xip_mem 2015-02-16 17:56:03 -08:00
pipe.c
pnode.c mnt: Move the clear of MNT_LOCKED from copy_tree to it's callers. 2014-12-02 10:46:50 -06:00
pnode.h
posix_acl.c
proc_namespace.c vfs: make mounts and mountstats honor root dir like mountinfo does 2014-12-17 08:27:15 -05:00
read_write.c locks: convert posix locks to file_lock_context 2015-01-16 16:08:16 -05:00
readdir.c vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
select.c all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
seq_file.c bitmap, cpumask, nodemask: remove dedicated formatting functions 2015-02-13 21:21:39 -08:00
signalfd.c fs: Convert show_fdinfo functions to void 2014-11-05 14:13:23 -05:00
splice.c vfs: export do_splice_direct() to modules 2014-10-24 00:14:35 +02:00
stack.c fs: fix comment for 'CONFIG_LBADF' 2014-08-26 09:35:56 +02:00
stat.c
statfs.c
super.c Merge branch 'akpm' (patches from Andrew) 2015-02-12 18:54:28 -08:00
sync.c kill f_dentry uses 2014-11-19 13:01:25 -05:00
timerfd.c fs: Convert show_fdinfo functions to void 2014-11-05 14:13:23 -05:00
utimes.c
xattr.c new helper: audit_file() 2014-11-19 13:01:26 -05:00