* [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 6:16 ` Vipin Sharma
0 siblings, 0 replies; 19+ messages in thread
From: Vipin Sharma @ 2022-02-17 6:16 UTC (permalink / raw)
To: pbonzini, seanjc
Cc: mkoutny, tj, lizefan.x, hannes, dmatlack, jiangshanlai, kvm,
cgroups, linux-kernel, Vipin Sharma
VM worker kthreads can linger in the VM process's cgroup for sometime
after KVM terminates the VM process.
KVM terminates the worker kthreads by calling kthread_stop() which waits
on the 'exited' completion, triggered by exit_mm(), via mm_release(), in
do_exit() during the kthread's exit. However, these kthreads are
removed from the cgroup using the cgroup_exit() which happens after the
exit_mm(). Therefore, a VM process can terminate in between the
exit_mm() and cgroup_exit() calls, leaving only worker kthreads in the
cgroup.
Moving worker kthreads back to the original cgroup (kthreadd_task's
cgroup) makes sure that the cgroup is empty as soon as the main VM
process is terminated.
Signed-off-by: Vipin Sharma <vipinsh@google.com>
---
v3:
- Use 'current->real_parent' (kthreadd_task) in the
cgroup_attach_task_all() call.
- Revert cgroup APIs changes in v2. Now, patch does not touch cgroup
APIs.
- Update commit and comment message
v2: https://lore.kernel.org/lkml/20211222225350.1912249-1-vipinsh@google.com/
- Use kthreadd_task in the cgroup API to avoid build issue.
v1: https://lore.kernel.org/lkml/20211214050708.4040200-1-vipinsh@google.com/
virt/kvm/kvm_main.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 83c57bcc6eb6..2c9dcfffb606 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5813,7 +5813,7 @@ static int kvm_vm_worker_thread(void *context)
struct kvm *kvm = init_context->kvm;
kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
uintptr_t data = init_context->data;
- int err;
+ int err, reattach_err;
err = kthread_park(current);
/* kthread_park(current) is never supposed to return an error */
@@ -5836,7 +5836,7 @@ static int kvm_vm_worker_thread(void *context)
init_context = NULL;
if (err)
- return err;
+ goto out;
/* Wait to be woken up by the spawner before proceeding. */
kthread_parkme();
@@ -5844,6 +5844,23 @@ static int kvm_vm_worker_thread(void *context)
if (!kthread_should_stop())
err = thread_fn(kvm, data);
+out:
+ /*
+ * Move kthread back to its original cgroup to prevent it lingering in
+ * the cgroup of the VM process, after the latter finishes its
+ * execution.
+ *
+ * kthread_stop() waits on the 'exited' completion condition which is
+ * set in exit_mm(), via mm_release(), in do_exit(). However, the
+ * kthread is removed from the cgroup in the cgroup_exit() which is
+ * called after the exit_mm(). This causes the kthread_stop() to return
+ * before the kthread actually quits the cgroup.
+ */
+ reattach_err = cgroup_attach_task_all(current->real_parent, current);
+ if (reattach_err) {
+ kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
+ __func__, reattach_err);
+ }
return err;
}
base-commit: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
--
2.35.1.265.g69c8d7142f-goog
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 6:16 ` Vipin Sharma
0 siblings, 0 replies; 19+ messages in thread
From: Vipin Sharma @ 2022-02-17 6:16 UTC (permalink / raw)
To: pbonzini-H+wXaHxf7aLQT0dZR+AlfA, seanjc-hpIqsD4AKlfQT0dZR+AlfA
Cc: mkoutny-IBi9RG/b67k, tj-DgEjT+Ai2ygdnm+yROfE0A,
lizefan.x-EC8Uxl6Npydl57MIdRCFDg, hannes-druUgvl0LCNAfugRpC6u6w,
dmatlack-hpIqsD4AKlfQT0dZR+AlfA,
jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w, kvm-u79uwXL29TY76Z2rM5mHXA,
cgroups-u79uwXL29TY76Z2rM5mHXA,
linux-kernel-u79uwXL29TY76Z2rM5mHXA, Vipin Sharma
VM worker kthreads can linger in the VM process's cgroup for sometime
after KVM terminates the VM process.
KVM terminates the worker kthreads by calling kthread_stop() which waits
on the 'exited' completion, triggered by exit_mm(), via mm_release(), in
do_exit() during the kthread's exit. However, these kthreads are
removed from the cgroup using the cgroup_exit() which happens after the
exit_mm(). Therefore, a VM process can terminate in between the
exit_mm() and cgroup_exit() calls, leaving only worker kthreads in the
cgroup.
Moving worker kthreads back to the original cgroup (kthreadd_task's
cgroup) makes sure that the cgroup is empty as soon as the main VM
process is terminated.
Signed-off-by: Vipin Sharma <vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
v3:
- Use 'current->real_parent' (kthreadd_task) in the
cgroup_attach_task_all() call.
- Revert cgroup APIs changes in v2. Now, patch does not touch cgroup
APIs.
- Update commit and comment message
v2: https://lore.kernel.org/lkml/20211222225350.1912249-1-vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org/
- Use kthreadd_task in the cgroup API to avoid build issue.
v1: https://lore.kernel.org/lkml/20211214050708.4040200-1-vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org/
virt/kvm/kvm_main.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 83c57bcc6eb6..2c9dcfffb606 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5813,7 +5813,7 @@ static int kvm_vm_worker_thread(void *context)
struct kvm *kvm = init_context->kvm;
kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
uintptr_t data = init_context->data;
- int err;
+ int err, reattach_err;
err = kthread_park(current);
/* kthread_park(current) is never supposed to return an error */
@@ -5836,7 +5836,7 @@ static int kvm_vm_worker_thread(void *context)
init_context = NULL;
if (err)
- return err;
+ goto out;
/* Wait to be woken up by the spawner before proceeding. */
kthread_parkme();
@@ -5844,6 +5844,23 @@ static int kvm_vm_worker_thread(void *context)
if (!kthread_should_stop())
err = thread_fn(kvm, data);
+out:
+ /*
+ * Move kthread back to its original cgroup to prevent it lingering in
+ * the cgroup of the VM process, after the latter finishes its
+ * execution.
+ *
+ * kthread_stop() waits on the 'exited' completion condition which is
+ * set in exit_mm(), via mm_release(), in do_exit(). However, the
+ * kthread is removed from the cgroup in the cgroup_exit() which is
+ * called after the exit_mm(). This causes the kthread_stop() to return
+ * before the kthread actually quits the cgroup.
+ */
+ reattach_err = cgroup_attach_task_all(current->real_parent, current);
+ if (reattach_err) {
+ kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
+ __func__, reattach_err);
+ }
return err;
}
base-commit: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
--
2.35.1.265.g69c8d7142f-goog
^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
2022-02-17 6:16 ` Vipin Sharma
(?)
@ 2022-02-17 12:34 ` kernel test robot
-1 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 12:34 UTC (permalink / raw)
To: Vipin Sharma, pbonzini, seanjc
Cc: kbuild-all, mkoutny, tj, lizefan.x, hannes, dmatlack,
jiangshanlai, kvm, cgroups, linux-kernel, Vipin Sharma
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: s390-randconfig-s032-20220217 (https://download.01.org/0day-ci/archive/20220217/202202172046.GuW8pHQc-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=s390 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
arch/s390/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/s390/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/s390/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 12:34 ` kernel test robot
0 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 12:34 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 4800 bytes --]
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: s390-randconfig-s032-20220217 (https://download.01.org/0day-ci/archive/20220217/202202172046.GuW8pHQc-lkp(a)intel.com/config)
compiler: s390-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=s390 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
arch/s390/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/s390/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/s390/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 12:34 ` kernel test robot
0 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 12:34 UTC (permalink / raw)
To: Vipin Sharma, pbonzini-H+wXaHxf7aLQT0dZR+AlfA,
seanjc-hpIqsD4AKlfQT0dZR+AlfA
Cc: kbuild-all-hn68Rpc1hR1g9hUCZPvPmw, mkoutny-IBi9RG/b67k,
tj-DgEjT+Ai2ygdnm+yROfE0A, lizefan.x-EC8Uxl6Npydl57MIdRCFDg,
hannes-druUgvl0LCNAfugRpC6u6w, dmatlack-hpIqsD4AKlfQT0dZR+AlfA,
jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w, kvm-u79uwXL29TY76Z2rM5mHXA,
cgroups-u79uwXL29TY76Z2rM5mHXA,
linux-kernel-u79uwXL29TY76Z2rM5mHXA, Vipin Sharma
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: s390-randconfig-s032-20220217 (https://download.01.org/0day-ci/archive/20220217/202202172046.GuW8pHQc-lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org/config)
compiler: s390-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=s390 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
sparse warnings: (new ones prefixed by >>)
arch/s390/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/s390/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/s390/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/s390/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
2022-02-17 12:34 ` kernel test robot
(?)
@ 2022-02-17 16:05 ` Paolo Bonzini
-1 siblings, 0 replies; 19+ messages in thread
From: Paolo Bonzini @ 2022-02-17 16:05 UTC (permalink / raw)
To: kernel test robot, Vipin Sharma, seanjc
Cc: kbuild-all, mkoutny, tj, lizefan.x, hannes, dmatlack,
jiangshanlai, kvm, cgroups, linux-kernel
On 2/17/22 13:34, kernel test robot wrote:
>> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
This needs to be within rcu_dereference().
Paolo
> 5860 if (reattach_err) {
> 5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
> 5862 __func__, reattach_err);
> 5863 }
> 5864 return err;
> 5865 }
> 5866
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 16:05 ` Paolo Bonzini
0 siblings, 0 replies; 19+ messages in thread
From: Paolo Bonzini @ 2022-02-17 16:05 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 531 bytes --]
On 2/17/22 13:34, kernel test robot wrote:
>> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
This needs to be within rcu_dereference().
Paolo
> 5860 if (reattach_err) {
> 5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
> 5862 __func__, reattach_err);
> 5863 }
> 5864 return err;
> 5865 }
> 5866
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
>
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 16:05 ` Paolo Bonzini
0 siblings, 0 replies; 19+ messages in thread
From: Paolo Bonzini @ 2022-02-17 16:05 UTC (permalink / raw)
To: kernel test robot, Vipin Sharma, seanjc-hpIqsD4AKlfQT0dZR+AlfA
Cc: kbuild-all-hn68Rpc1hR1g9hUCZPvPmw, mkoutny-IBi9RG/b67k,
tj-DgEjT+Ai2ygdnm+yROfE0A, lizefan.x-EC8Uxl6Npydl57MIdRCFDg,
hannes-druUgvl0LCNAfugRpC6u6w, dmatlack-hpIqsD4AKlfQT0dZR+AlfA,
jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w, kvm-u79uwXL29TY76Z2rM5mHXA,
cgroups-u79uwXL29TY76Z2rM5mHXA,
linux-kernel-u79uwXL29TY76Z2rM5mHXA
On 2/17/22 13:34, kernel test robot wrote:
>> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
This needs to be within rcu_dereference().
Paolo
> 5860 if (reattach_err) {
> 5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
> 5862 __func__, reattach_err);
> 5863 }
> 5864 return err;
> 5865 }
> 5866
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org
>
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
2022-02-17 6:16 ` Vipin Sharma
(?)
@ 2022-02-17 19:47 ` kernel test robot
-1 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 19:47 UTC (permalink / raw)
To: Vipin Sharma, pbonzini, seanjc
Cc: kbuild-all, mkoutny, tj, lizefan.x, hannes, dmatlack,
jiangshanlai, kvm, cgroups, linux-kernel, Vipin Sharma
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: arm64-randconfig-s032-20220217 (https://download.01.org/0day-ci/archive/20220218/202202180218.msk1UR5R-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=arm64 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
arch/arm64/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_change_pte' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_start' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_end' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_flush_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_test_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/arm64/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 19:47 ` kernel test robot
0 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 19:47 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 5825 bytes --]
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: arm64-randconfig-s032-20220217 (https://download.01.org/0day-ci/archive/20220218/202202180218.msk1UR5R-lkp(a)intel.com/config)
compiler: aarch64-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=arm64 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
arch/arm64/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_change_pte' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_start' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_end' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_flush_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_test_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/arm64/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 19:47 ` kernel test robot
0 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 19:47 UTC (permalink / raw)
To: Vipin Sharma, pbonzini-H+wXaHxf7aLQT0dZR+AlfA,
seanjc-hpIqsD4AKlfQT0dZR+AlfA
Cc: kbuild-all-hn68Rpc1hR1g9hUCZPvPmw, mkoutny-IBi9RG/b67k,
tj-DgEjT+Ai2ygdnm+yROfE0A, lizefan.x-EC8Uxl6Npydl57MIdRCFDg,
hannes-druUgvl0LCNAfugRpC6u6w, dmatlack-hpIqsD4AKlfQT0dZR+AlfA,
jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w, kvm-u79uwXL29TY76Z2rM5mHXA,
cgroups-u79uwXL29TY76Z2rM5mHXA,
linux-kernel-u79uwXL29TY76Z2rM5mHXA, Vipin Sharma
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: arm64-randconfig-s032-20220217 (https://download.01.org/0day-ci/archive/20220218/202202180218.msk1UR5R-lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org/config)
compiler: aarch64-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=arm64 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
sparse warnings: (new ones prefixed by >>)
arch/arm64/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_change_pte' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_start' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_end' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_flush_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_test_young' - different lock contexts for basic block
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/arm64/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
2022-02-17 6:16 ` Vipin Sharma
(?)
@ 2022-02-17 23:22 ` kernel test robot
-1 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 23:22 UTC (permalink / raw)
To: Vipin Sharma, pbonzini, seanjc
Cc: kbuild-all, mkoutny, tj, lizefan.x, hannes, dmatlack,
jiangshanlai, kvm, cgroups, linux-kernel, Vipin Sharma
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: x86_64-rhel-8.3-kselftests (https://download.01.org/0day-ci/archive/20220218/202202180730.AAgeOZkF-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
arch/x86/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_change_pte' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_start' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_end' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_flush_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_test_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/x86/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 23:22 ` kernel test robot
0 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 23:22 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 5600 bytes --]
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: x86_64-rhel-8.3-kselftests (https://download.01.org/0day-ci/archive/20220218/202202180730.AAgeOZkF-lkp(a)intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
arch/x86/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_change_pte' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_start' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_end' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_flush_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_test_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/x86/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-17 23:22 ` kernel test robot
0 siblings, 0 replies; 19+ messages in thread
From: kernel test robot @ 2022-02-17 23:22 UTC (permalink / raw)
To: Vipin Sharma, pbonzini-H+wXaHxf7aLQT0dZR+AlfA,
seanjc-hpIqsD4AKlfQT0dZR+AlfA
Cc: kbuild-all-hn68Rpc1hR1g9hUCZPvPmw, mkoutny-IBi9RG/b67k,
tj-DgEjT+Ai2ygdnm+yROfE0A, lizefan.x-EC8Uxl6Npydl57MIdRCFDg,
hannes-druUgvl0LCNAfugRpC6u6w, dmatlack-hpIqsD4AKlfQT0dZR+AlfA,
jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w, kvm-u79uwXL29TY76Z2rM5mHXA,
cgroups-u79uwXL29TY76Z2rM5mHXA,
linux-kernel-u79uwXL29TY76Z2rM5mHXA, Vipin Sharma
Hi Vipin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on db6e7adf8de9b3b99a9856acb73870cc3a70e3ca]
url: https://github.com/0day-ci/linux/commits/Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
base: db6e7adf8de9b3b99a9856acb73870cc3a70e3ca
config: x86_64-rhel-8.3-kselftests (https://download.01.org/0day-ci/archive/20220218/202202180730.AAgeOZkF-lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/1abffef71ef85b6fb8f1296e6ef38febc4f2b007
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Vipin-Sharma/KVM-Move-VM-s-worker-kthreads-back-to-the-original-cgroup-before-exiting/20220217-141723
git checkout 1abffef71ef85b6fb8f1296e6ef38febc4f2b007
# save the config file to linux build tree
mkdir build_dir
make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
sparse warnings: (new ones prefixed by >>)
arch/x86/kvm/../../../virt/kvm/kvm_main.c: note: in included file:
include/linux/kvm_host.h:1877:54: sparse: sparse: array of flexible structures
include/linux/kvm_host.h:1879:56: sparse: sparse: array of flexible structures
>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *from @@ got struct task_struct [noderef] __rcu *real_parent @@
arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: expected struct task_struct *from
arch/x86/kvm/../../../virt/kvm/kvm_main.c:5859:54: sparse: got struct task_struct [noderef] __rcu *real_parent
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_change_pte' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_start' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_invalidate_range_end' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_flush_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_clear_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:538:9: sparse: sparse: context imbalance in 'kvm_mmu_notifier_test_young' - different lock contexts for basic block
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2522:9: sparse: sparse: context imbalance in 'hva_to_pfn_remapped' - unexpected unlock
vim +5859 arch/x86/kvm/../../../virt/kvm/kvm_main.c
5805
5806 static int kvm_vm_worker_thread(void *context)
5807 {
5808 /*
5809 * The init_context is allocated on the stack of the parent thread, so
5810 * we have to locally copy anything that is needed beyond initialization
5811 */
5812 struct kvm_vm_worker_thread_context *init_context = context;
5813 struct kvm *kvm = init_context->kvm;
5814 kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
5815 uintptr_t data = init_context->data;
5816 int err, reattach_err;
5817
5818 err = kthread_park(current);
5819 /* kthread_park(current) is never supposed to return an error */
5820 WARN_ON(err != 0);
5821 if (err)
5822 goto init_complete;
5823
5824 err = cgroup_attach_task_all(init_context->parent, current);
5825 if (err) {
5826 kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
5827 __func__, err);
5828 goto init_complete;
5829 }
5830
5831 set_user_nice(current, task_nice(init_context->parent));
5832
5833 init_complete:
5834 init_context->err = err;
5835 complete(&init_context->init_done);
5836 init_context = NULL;
5837
5838 if (err)
5839 goto out;
5840
5841 /* Wait to be woken up by the spawner before proceeding. */
5842 kthread_parkme();
5843
5844 if (!kthread_should_stop())
5845 err = thread_fn(kvm, data);
5846
5847 out:
5848 /*
5849 * Move kthread back to its original cgroup to prevent it lingering in
5850 * the cgroup of the VM process, after the latter finishes its
5851 * execution.
5852 *
5853 * kthread_stop() waits on the 'exited' completion condition which is
5854 * set in exit_mm(), via mm_release(), in do_exit(). However, the
5855 * kthread is removed from the cgroup in the cgroup_exit() which is
5856 * called after the exit_mm(). This causes the kthread_stop() to return
5857 * before the kthread actually quits the cgroup.
5858 */
> 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
5860 if (reattach_err) {
5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
5862 __func__, reattach_err);
5863 }
5864 return err;
5865 }
5866
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
2022-02-17 16:05 ` Paolo Bonzini
(?)
@ 2022-02-19 0:30 ` Sean Christopherson
-1 siblings, 0 replies; 19+ messages in thread
From: Sean Christopherson @ 2022-02-19 0:30 UTC (permalink / raw)
To: Paolo Bonzini
Cc: kernel test robot, Vipin Sharma, kbuild-all, mkoutny, tj,
lizefan.x, hannes, dmatlack, jiangshanlai, kvm, cgroups,
linux-kernel
On Thu, Feb 17, 2022, Paolo Bonzini wrote:
> On 2/17/22 13:34, kernel test robot wrote:
> > > 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
>
> This needs to be within rcu_dereference().
As Vipin found out the hard way, cgroup_attach_task_all() can't be inside an RCU
critical section as it might sleep due to mutex_lock().
My sched knowledge is sketchy at best, but I believe KVM just needs to guarantee
the liveliness of real_parent when passing it to cgroup_attach_task_all().
Presumably kthreadd_task can (in theory) be killed/exiting while this is going on,
but at that point I doubt anyone cares much about cgroup accuracy.
So I think this can be:
rcu_read_lock();
parent = rcu_dereference(current->real_parent);
get_task_struct(parent);
rcu_read_unlock();
(void)cgroup_attach_task_all(parent, current);
put_task_struct(parent);
> > 5860 if (reattach_err) {
> > 5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
> > 5862 __func__, reattach_err);
Eh, I wouldn't bother logging the error, userspace can't take action on it, and
if the system is OOM it's just more noise in the log to dig through.
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-19 0:30 ` Sean Christopherson
0 siblings, 0 replies; 19+ messages in thread
From: Sean Christopherson @ 2022-02-19 0:30 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 1223 bytes --]
On Thu, Feb 17, 2022, Paolo Bonzini wrote:
> On 2/17/22 13:34, kernel test robot wrote:
> > > 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
>
> This needs to be within rcu_dereference().
As Vipin found out the hard way, cgroup_attach_task_all() can't be inside an RCU
critical section as it might sleep due to mutex_lock().
My sched knowledge is sketchy at best, but I believe KVM just needs to guarantee
the liveliness of real_parent when passing it to cgroup_attach_task_all().
Presumably kthreadd_task can (in theory) be killed/exiting while this is going on,
but at that point I doubt anyone cares much about cgroup accuracy.
So I think this can be:
rcu_read_lock();
parent = rcu_dereference(current->real_parent);
get_task_struct(parent);
rcu_read_unlock();
(void)cgroup_attach_task_all(parent, current);
put_task_struct(parent);
> > 5860 if (reattach_err) {
> > 5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
> > 5862 __func__, reattach_err);
Eh, I wouldn't bother logging the error, userspace can't take action on it, and
if the system is OOM it's just more noise in the log to dig through.
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-19 0:30 ` Sean Christopherson
0 siblings, 0 replies; 19+ messages in thread
From: Sean Christopherson @ 2022-02-19 0:30 UTC (permalink / raw)
To: Paolo Bonzini
Cc: kernel test robot, Vipin Sharma,
kbuild-all-hn68Rpc1hR1g9hUCZPvPmw, mkoutny-IBi9RG/b67k,
tj-DgEjT+Ai2ygdnm+yROfE0A, lizefan.x-EC8Uxl6Npydl57MIdRCFDg,
hannes-druUgvl0LCNAfugRpC6u6w, dmatlack-hpIqsD4AKlfQT0dZR+AlfA,
jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w, kvm-u79uwXL29TY76Z2rM5mHXA,
cgroups-u79uwXL29TY76Z2rM5mHXA,
linux-kernel-u79uwXL29TY76Z2rM5mHXA
On Thu, Feb 17, 2022, Paolo Bonzini wrote:
> On 2/17/22 13:34, kernel test robot wrote:
> > > 5859 reattach_err = cgroup_attach_task_all(current->real_parent, current);
>
> This needs to be within rcu_dereference().
As Vipin found out the hard way, cgroup_attach_task_all() can't be inside an RCU
critical section as it might sleep due to mutex_lock().
My sched knowledge is sketchy at best, but I believe KVM just needs to guarantee
the liveliness of real_parent when passing it to cgroup_attach_task_all().
Presumably kthreadd_task can (in theory) be killed/exiting while this is going on,
but at that point I doubt anyone cares much about cgroup accuracy.
So I think this can be:
rcu_read_lock();
parent = rcu_dereference(current->real_parent);
get_task_struct(parent);
rcu_read_unlock();
(void)cgroup_attach_task_all(parent, current);
put_task_struct(parent);
> > 5860 if (reattach_err) {
> > 5861 kvm_err("%s: cgroup_attach_task_all failed on reattach with err %d\n",
> > 5862 __func__, reattach_err);
Eh, I wouldn't bother logging the error, userspace can't take action on it, and
if the system is OOM it's just more noise in the log to dig through.
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
2022-02-19 0:30 ` Sean Christopherson
@ 2022-02-19 7:55 ` Paolo Bonzini
-1 siblings, 0 replies; 19+ messages in thread
From: Paolo Bonzini @ 2022-02-19 7:55 UTC (permalink / raw)
To: Sean Christopherson
Cc: kernel test robot, Vipin Sharma, kbuild-all, mkoutny, tj,
lizefan.x, hannes, dmatlack, jiangshanlai, kvm, cgroups,
linux-kernel
On 2/19/22 01:30, Sean Christopherson wrote:
>
> So I think this can be:
>
> rcu_read_lock();
> parent = rcu_dereference(current->real_parent);
> get_task_struct(parent);
> rcu_read_unlock();
>
> (void)cgroup_attach_task_all(parent, current);
> put_task_struct(parent);
Yes, I agree.
Paolo
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting.
@ 2022-02-19 7:55 ` Paolo Bonzini
0 siblings, 0 replies; 19+ messages in thread
From: Paolo Bonzini @ 2022-02-19 7:55 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 322 bytes --]
On 2/19/22 01:30, Sean Christopherson wrote:
>
> So I think this can be:
>
> rcu_read_lock();
> parent = rcu_dereference(current->real_parent);
> get_task_struct(parent);
> rcu_read_unlock();
>
> (void)cgroup_attach_task_all(parent, current);
> put_task_struct(parent);
Yes, I agree.
Paolo
^ permalink raw reply [flat|nested] 19+ messages in thread
end of thread, other threads:[~2022-02-19 7:55 UTC | newest]
Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-17 6:16 [PATCH v3] KVM: Move VM's worker kthreads back to the original cgroup before exiting Vipin Sharma
2022-02-17 6:16 ` Vipin Sharma
2022-02-17 12:34 ` kernel test robot
2022-02-17 12:34 ` kernel test robot
2022-02-17 12:34 ` kernel test robot
2022-02-17 16:05 ` Paolo Bonzini
2022-02-17 16:05 ` Paolo Bonzini
2022-02-17 16:05 ` Paolo Bonzini
2022-02-19 0:30 ` Sean Christopherson
2022-02-19 0:30 ` Sean Christopherson
2022-02-19 0:30 ` Sean Christopherson
2022-02-19 7:55 ` Paolo Bonzini
2022-02-19 7:55 ` Paolo Bonzini
2022-02-17 19:47 ` kernel test robot
2022-02-17 19:47 ` kernel test robot
2022-02-17 19:47 ` kernel test robot
2022-02-17 23:22 ` kernel test robot
2022-02-17 23:22 ` kernel test robot
2022-02-17 23:22 ` kernel test robot
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