The patch titled
cgroup: fix a race condition in manipulating tsk->cg_list
has been removed from the -mm tree. Its filename was
cgroup-fix-a-race-condition-in-manipulating-tsk-cg_list.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: cgroup: fix a race condition in manipulating tsk->cg_list
From: Li Zefan <lizf@xxxxxxxxxxxxxx>
When I ran a test program to fork mass processes and at the same time 'cat
/cgroup/tasks', I got the following oops:
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:72!
invalid opcode: 0000 [#1] SMP
Pid: 4178, comm: a.out Not tainted (2.6.25-rc9 #72)
...
Call Trace:
[<c044a5f9>] ? cgroup_exit+0x55/0x94
[<c0427acf>] ? do_exit+0x217/0x5ba
[<c0427ed7>] ? do_group_exit+0.65/0x7c
[<c0427efd>] ? sys_exit_group+0xf/0x11
[<c0404842>] ? syscall_call+0x7/0xb
[<c05e0000>] ? init_cyrix+0x2fa/0x479
...
EIP: [<c04df671>] list_del+0x35/0x53 SS:ESP 0068:ebc7df4
---[ end trace caffb7332252612b ]---
Fixing recursive fault but reboot is needed!
After digging into the code and debugging, I finlly found out a race
situation:
do_exit()
->cgroup_exit()
->if (!list_empty(&tsk->cg_list))
list_del(&tsk->cg_list);
cgroup_iter_start()
->cgroup_enable_task_cg_list()
->list_add(&tsk->cg_list, ..);
In this case the list won't be deleted though the process has exited.
We got two bug reports in the past, which seem to be the same bug as
this one:
http://lkml.org/lkml/2008/3/5/332
http://lkml.org/lkml/2007/10/17/224
Actually sometimes I got oops on list_del, sometimes oops on list_add.
And I can change my test program a bit to trigger other oops.
The patch has been tested both on x86_32 and x86_64.
Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Paul Jackson <pj@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN kernel/cgroup.c~cgroup-fix-a-race-condition-in-manipulating-tsk-cg_list kernel/cgroup.c
--- a/kernel/cgroup.c~cgroup-fix-a-race-condition-in-manipulating-tsk-cg_list
+++ a/kernel/cgroup.c
@@ -1722,7 +1722,12 @@ void cgroup_enable_task_cg_lists(void)
use_task_css_set_links = 1;
do_each_thread(g, p) {
task_lock(p);
- if (list_empty(&p->cg_list))
+ /*
+ * We should check if the process is exiting, otherwise
+ * it will race with cgroup_exit() in that the list
+ * entry won't be deleted though the process has exited.
+ */
+ if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
list_add(&p->cg_list, &p->cgroups->tasks);
task_unlock(p);
} while_each_thread(g, p);
_
Patches currently in -mm which might be from lizf@xxxxxxxxxxxxxx are
origin.patch
acpi-check-a-return-value-correctly-in-acpi_power_get_context.patch
oom_kill-remove-unused-parameter-in-badness.patch
cgroup-api-files-rename-read-write_uint-methods-to-read_write_u64.patch
cgroup-api-files-add-res_counter_read_u64.patch
cgroup-api-files-use-read_u64-in-memory-controller.patch
cgroup-api-files-strip-all-trailing-whitespace-in-cgroup_write_u64.patch
revert-part-of-sched-cpuset-customize-sched-domains-core.patch
cgroup-api-files-update-cpusets-to-use-cgroup-structured-file-api.patch
reapply-sched-cpuset-customize-sched-domains-core-bits.patch
cgroup-api-files-update-cpusets-to-use-cgroup-structured-file-api-fix.patch
cgroup-api-files-add-cgroup-map-data-type.patch
cgroup-api-files-use-cgroup-map-for-memcontrol-stats-file.patch
cgroup-api-files-drop-mem_cgroup_force_empty.patch
cgroup-api-files-move-releasable-to-cgroup_debug-subsystem.patch
cgroup-api-files-make-cgroup_debug-default-to-off.patch
cgroup-annotate-cgroup_init_subsys-with-__init.patch
cgroup-switch-to-proc_create.patch
cgroups-implement-device-whitelist-v6.patch
cgroups-implement-device-whitelist-v6-checkpatch-fixes.patch
cgroups-implement-device-whitelist-v6-cleanups.patch
cgroups-implement-device-whitelist-doc.patch
cgroups-implement-device-whitelist-v6-fix.patch
cgroups-use-a-hash-table-for-css_set-finding.patch
cgroups-simplify-init_subsys.patch
cgroups-remove-the-css_set-linked-list.patch
add-a-document-describing-the-resource-counter-abstraction-v2-fix.patch
use-vmalloc-for-mem_cgroup-allocation-v3.patch
use-vmalloc-for-mem_cgroup-allocation-v3-simplification.patch
cpuset-hardwall-flag-switch-cpusets-to-use-the-bulk-cgroup_add_files-api.patch
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