[linus:master] [fs] 761475268f: BUG:KCSAN:data-race_in_atime_needs_update/touch_atime

From: kernel test robot

Date: Thu Feb 26 2026 - 08:03:56 EST

Hello,

it seems to us this change causes the stats changes for various (random)
KCSAN issues. just FYI what we observed in tests.

=========================================================================================
tbox_group/testcase/rootfs/kconfig/compiler/runtime/group/nr_groups:
vm-snb/trinity/yocto-i386-minimal-20190520.cgz/x86_64-randconfig-013-20260223/gcc-14/300s/group-01/5

1cbc822816758b26 761475268fa8e322fe6b80bcf55
---------------- ---------------------------
fail:runs %reproduction fail:runs
| | |
1:200 2% 4:200 dmesg.BUG:KCSAN:data-race_in_alloc_pid/copy_process
1:200 -0% :200 dmesg.BUG:KCSAN:data-race_in_atime_needs_update/inode_set_ctime_current
32:200 -16% :200 dmesg.BUG:KCSAN:data-race_in_atime_needs_update/inode_update_timestamps
:200 17% 34:200 dmesg.BUG:KCSAN:data-race_in_atime_needs_update/touch_atime
1:200 0% 1:200 dmesg.BUG:KCSAN:data-race_in_credit_init_bits/try_to_generate_entropy
2:200 -1% :200 dmesg.BUG:KCSAN:data-race_in_crng_reseed/try_to_generate_entropy
1:200 1% 3:200 dmesg.BUG:KCSAN:data-race_in_file_update_time_flags/inode_set_ctime_current
2:200 -1% :200 dmesg.BUG:KCSAN:data-race_in_file_update_time_flags/inode_update_timestamps
6:200 -3% :200 dmesg.BUG:KCSAN:data-race_in_generic_fillattr/inode_update_timestamps
:200 6% 11:200 dmesg.BUG:KCSAN:data-race_in_generic_fillattr/touch_atime
:200 1% 2:200 dmesg.BUG:KCSAN:data-race_in_inode_set_ctime_current/inode_update_time
22:200 -11% :200 dmesg.BUG:KCSAN:data-race_in_inode_update_timestamps/inode_update_timestamps
:200 10% 20:200 dmesg.BUG:KCSAN:data-race_in_touch_atime/touch_atime

kernel test robot noticed "BUG:KCSAN:data-race_in_atime_needs_update/touch_atime" on:

commit: 761475268fa8e322fe6b80bcf557dc65517df71e ("fs: refactor ->update_time handling")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: trinity
version:
with following parameters:

runtime: 300s
group: group-01
nr_groups: 5

config: x86_64-randconfig-013-20260223
compiler: gcc-14
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 32G

(please refer to attached dmesg/kmsg for entire log/backtrace)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-lkp/202602262015.d00ee0c9-lkp@xxxxxxxxx

[ 180.177701][T23712] BUG: KCSAN: data-race in atime_needs_update / touch_atime
[ 180.178300][T23712]
[ 180.178556][T23712] write to 0xffff8881005bf140 of 4 bytes by task 23711 on cpu 0:
[ 180.179221][T23712] touch_atime (include/linux/fs.h:1624 fs/inode.c:2092 fs/inode.c:2135 fs/inode.c:2158 fs/inode.c:2236)
[ 180.179620][T23712] pick_link (fs/namei.c:1989)
[ 180.180009][T23712] step_into_slowpath (fs/namei.c:2066)
[ 180.180442][T23712] open_last_lookups (fs/namei.c:2091 fs/namei.c:4575)
[ 180.180870][T23712] path_openat (fs/namei.c:4784)
[ 180.181260][T23712] do_filp_open (fs/namei.c:4814)
[ 180.181665][T23712] do_open_execat (fs/exec.c:783)
[ 180.184266][T23712] open_exec (fs/exec.c:823)
[ 180.184645][T23712] load_elf_binary (include/linux/slab.h:957 fs/binfmt_elf.c:919)
[ 180.185075][T23712] exec_binprm (fs/exec.c:1671 fs/exec.c:1701)
[ 180.185469][T23712] bprm_execve (fs/exec.c:1735)
[ 180.185898][T23712] bprm_execve (fs/exec.c:1781)
[ 180.186295][T23712] kernel_execve (fs/exec.c:1919)
[ 180.186707][T23712] call_usermodehelper_exec_async (kernel/umh.c:113)
[ 180.187226][T23712] ret_from_fork (arch/x86/kernel/process.c:164)
[ 180.187637][T23712] ret_from_fork_asm (arch/x86/entry/entry_64.S:256)
[ 180.188059][T23712]
[ 180.188315][T23712] read to 0xffff8881005bf140 of 4 bytes by task 23712 on cpu 1:
[ 180.188962][T23712] atime_needs_update (fs/inode.c:2056 fs/inode.c:2201)
[ 180.189403][T23712] pick_link (fs/namei.c:1983 (discriminator 2))
[ 180.189795][T23712] step_into_slowpath (fs/namei.c:2066)
[ 180.190229][T23712] open_last_lookups (fs/namei.c:2091 fs/namei.c:4575)
[ 180.190657][T23712] path_openat (fs/namei.c:4784)
[ 180.191075][T23712] do_filp_open (fs/namei.c:4814)
[ 180.191479][T23712] do_open_execat (fs/exec.c:783)
[ 180.191885][T23712] open_exec (fs/exec.c:823)
[ 180.192256][T23712] load_elf_binary (include/linux/slab.h:957 fs/binfmt_elf.c:919)
[ 180.192683][T23712] exec_binprm (fs/exec.c:1671 fs/exec.c:1701)
[ 180.193082][T23712] bprm_execve (fs/exec.c:1735)
[ 180.193537][T23712] bprm_execve (fs/exec.c:1781)
[ 180.193922][T23712] kernel_execve (fs/exec.c:1919)
[ 180.194333][T23712] call_usermodehelper_exec_async (kernel/umh.c:113)
[ 180.194850][T23712] ret_from_fork (arch/x86/kernel/process.c:164)
[ 180.195265][T23712] ret_from_fork_asm (arch/x86/entry/entry_64.S:256)
[ 180.195684][T23712]
[ 180.195936][T23712] value changed: 0x2160ec00 -> 0x22921900
[ 180.196415][T23712]
[ 180.196667][T23712] Reported by Kernel Concurrency Sanitizer on:
[ 180.197175][T23712] CPU: 1 UID: 0 PID: 23712 Comm: kworker/u8:0 Not tainted 6.19.0-rc1-00005-g761475268fa8 #1 PREEMPT 0fd055f61ee6c01889a41da1288262ad66e4a70f
[ 180.198323][T23712] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 180.199162][T23712] ==================================================================

The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20260226/202602262015.d00ee0c9-lkp@xxxxxxxxx

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki