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* [PATCH] cgroup: fix missing cpus_read_{lock,unlock}() in cgroup_transfer_tasks()
@ 2023-05-17  7:45 Qi Zheng
  2023-05-17  7:51 ` Muchun Song
       [not found] ` <20230517074545.2045035-1-qi.zheng-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>
  0 siblings, 2 replies; 4+ messages in thread
From: Qi Zheng @ 2023-05-17  7:45 UTC (permalink / raw)
  To: tj-DgEjT+Ai2ygdnm+yROfE0A, lizefan.x-EC8Uxl6Npydl57MIdRCFDg,
	hannes-druUgvl0LCNAfugRpC6u6w
  Cc: cgroups-u79uwXL29TY76Z2rM5mHXA,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA,
	muchun.song-fxUVXftIFDnyG1zEObXtfA, Qi Zheng, Zhao Gongyi

From: Qi Zheng <zhengqi.arch-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>

The commit 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock()
deadlock") fixed the deadlock between cgroup_threadgroup_rwsem and
cpus_read_lock() by introducing cgroup_attach_{lock,unlock}() and removing
cpus_read_{lock,unlock}() from cpuset_attach(). But cgroup_transfer_tasks()
was missed and not handled, which will cause th following warning:

 WARNING: CPU: 0 PID: 589 at kernel/cpu.c:526 lockdep_assert_cpus_held+0x32/0x40
 CPU: 0 PID: 589 Comm: kworker/1:4 Not tainted 6.4.0-rc2-next-20230517 #50
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
 Workqueue: events cpuset_hotplug_workfn
 RIP: 0010:lockdep_assert_cpus_held+0x32/0x40
 <...>
 Call Trace:
  <TASK>
  cpuset_attach+0x40/0x240
  cgroup_migrate_execute+0x452/0x5e0
  ? _raw_spin_unlock_irq+0x28/0x40
  cgroup_transfer_tasks+0x1f3/0x360
  ? find_held_lock+0x32/0x90
  ? cpuset_hotplug_workfn+0xc81/0xed0
  cpuset_hotplug_workfn+0xcb1/0xed0
  ? process_one_work+0x248/0x5b0
  process_one_work+0x2b9/0x5b0
  worker_thread+0x56/0x3b0
  ? process_one_work+0x5b0/0x5b0
  kthread+0xf1/0x120
  ? kthread_complete_and_exit+0x20/0x20
  ret_from_fork+0x1f/0x30
  </TASK>

So just use the cgroup_attach_{lock,unlock}() helper to fix it.

Fixes: 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock")
Reported-by: Zhao Gongyi <zhaogongyi-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>
Signed-off-by: Qi Zheng <zhengqi.arch-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>
---
 kernel/cgroup/cgroup-v1.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index aeef06c465ef..5407241dbb45 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -108,7 +108,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 
 	cgroup_lock();
 
-	percpu_down_write(&cgroup_threadgroup_rwsem);
+	cgroup_attach_lock(true);
 
 	/* all tasks in @from are being moved, all csets are source */
 	spin_lock_irq(&css_set_lock);
@@ -144,7 +144,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 	} while (task && !ret);
 out_err:
 	cgroup_migrate_finish(&mgctx);
-	percpu_up_write(&cgroup_threadgroup_rwsem);
+	cgroup_attach_unlock(true);
 	cgroup_unlock();
 	return ret;
 }
-- 
2.30.2


^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-05-22 18:45 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2023-05-17  7:45 [PATCH] cgroup: fix missing cpus_read_{lock,unlock}() in cgroup_transfer_tasks() Qi Zheng
2023-05-17  7:51 ` Muchun Song
     [not found]   ` <75E872A8-652F-40B0-80D0-378569E77775-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>
2023-05-22  2:23     ` Qi Zheng
     [not found] ` <20230517074545.2045035-1-qi.zheng-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>
2023-05-22 18:45   ` Tejun Heo

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