On 7/29/24 22:55, chenridong wrote:
On 2024/7/30 10:34, Waiman Long wrote:
On 7/29/24 21:53, Chen Ridong wrote:
We find a bug as below:
BUG: unable to handle page fault for address: 00000003
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 358 Comm: bash Tainted: G W I 6.6.0-10893-g60d6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1
04/4
RIP: 0010:partition_sched_domains_locked+0x483/0x600
Code: 01 48 85 d2 74 0d 48 83 05 29 3f f8 03 01 f3 48 0f bc c2 89 c0
48 9
RSP: 0018:ffffc90000fdbc58 EFLAGS: 00000202
RAX: 0000000100000003 RBX: ffff888100b3dfa0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000002fe80
RBP: ffff888100b3dfb0 R08: 0000000000000001 R09: 0000000000000000
R10: ffffc90000fdbcb0 R11: 0000000000000004 R12: 0000000000000002
R13: ffff888100a92b48 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f44a5425740(0000) GS:ffff888237d80000(0000)
knlGS:0000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100030973 CR3: 000000010722c000 CR4: 00000000000006e0
Call Trace:
<TASK>
? show_regs+0x8c/0xa0
? __die_body+0x23/0xa0
? __die+0x3a/0x50
? page_fault_oops+0x1d2/0x5c0
? partition_sched_domains_locked+0x483/0x600
? search_module_extables+0x2a/0xb0
? search_exception_tables+0x67/0x90
? kernelmode_fixup_or_oops+0x144/0x1b0
? __bad_area_nosemaphore+0x211/0x360
? up_read+0x3b/0x50
? bad_area_nosemaphore+0x1a/0x30
? exc_page_fault+0x890/0xd90
? __lock_acquire.constprop.0+0x24f/0x8d0
? __lock_acquire.constprop.0+0x24f/0x8d0
? asm_exc_page_fault+0x26/0x30
? partition_sched_domains_locked+0x483/0x600
? partition_sched_domains_locked+0xf0/0x600
rebuild_sched_domains_locked+0x806/0xdc0
update_partition_sd_lb+0x118/0x130
cpuset_write_resmask+0xffc/0x1420
cgroup_file_write+0xb2/0x290
kernfs_fop_write_iter+0x194/0x290
new_sync_write+0xeb/0x160
vfs_write+0x16f/0x1d0
ksys_write+0x81/0x180
__x64_sys_write+0x21/0x30
x64_sys_call+0x2f25/0x4630
do_syscall_64+0x44/0xb0
entry_SYSCALL_64_after_hwframe+0x78/0xe2
RIP: 0033:0x7f44a553c887
It can be reproduced with cammands:
cd /sys/fs/cgroup/
mkdir test
cd test/
echo +cpuset > ../cgroup.subtree_control
echo root > cpuset.cpus.partition
echo 0-3 > cpuset.cpus // 3 is nproc
What do you mean by "3 is nproc"? Are there only 3 CPUs in the
system? What are the value of /sys/fs/cgroup/cpuset.cpu*?
Yes, I tested it with qemu, only 3 cpus are available.
# cat /sys/fs/cgroup/cpuset.cpus.effective
0-3
This case is taking all cpus away from root, test should fail to be a
valid root, it should not rebuild scheduling domains.
I see. So there are 4 CPUs in the systems. So nproc should be 4. That is
why I got confused when you said nproc is 3. I think you should clarify
this in your patch.
This issue is caused by the incorrect rebuilding of scheduling domains.
In this scenario, test/cpuset.cpus.partition should be an invalid root
and should not trigger the rebuilding of scheduling domains. When
calling
update_parent_effective_cpumask with partcmd_update, if newmask is not
null, it should recheck newmask whether there are cpus is available
for parect/cs that has tasks.
Fixes: 0c7f293efc87 ("cgroup/cpuset: Add
cpuset.cpus.exclusive.effective for v2")
Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 40ec4abaf440..a9b6d56eeffa 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1991,6 +1991,8 @@ static int
update_parent_effective_cpumask(struct cpuset *cs, int cmd,
part_error = PERR_CPUSEMPTY;
goto write_error;
}
+ /* Check newmask again, whether cpus are available for
parent/cs */
+ nocpu |= tasks_nocpu_error(parent, cs, newmask);
/*
* partcmd_update with newmask:
The code change looks reasonable to me. However, I would like to know
more about the reproduction steps.
I am OK with this patch other than missing some information in your
reproduction step.
Cheers,
Longman
