Hi Waiman,
On Mon, Apr 25, 2022 at 11:55:05AM -0400, Waiman Long wrote:
There are 3 places where the cpu and node masks of the top cpuset canI run some test, on a server with centOS, this did happen that
be initialized in the order they are executed:
1) start_kernel -> cpuset_init()
2) start_kernel -> cgroup_init() -> cpuset_bind()
3) kernel_init_freeable() -> do_basic_setup() -> cpuset_init_smp()
The first cpuset_init() function just sets all the bits in the masks.
The last one executed is cpuset_init_smp() which sets up cpu and node
masks suitable for v1, but not v2. cpuset_bind() does the right setup
for both v1 and v2.
For systems with cgroup v2 setup, cpuset_bind() is called once. For
systems with cgroup v1 setup, cpuset_bind() is called twice. It is
first called before cpuset_init_smp() in cgroup v2 mode. Then it is
called again when cgroup v1 filesystem is mounted in v1 mode after
cpuset_init_smp().
[ 2.609781] cpuset_bind() called - v2 = 1
[ 3.079473] cpuset_init_smp() called
[ 7.103710] cpuset_bind() called - v2 = 0
cpuset_bind() is called twice, first as v2 during kernel boot,
and then as v1 post-boot.
However on a QEMU running with a basic debian rootfs image,
the second call of cpuset_bind() didn't happen.
As a result, cpu and memory node hot add may fail to update the cpu andSo can we keep line
node masks of the top cpuset to include the newly added cpu or node in
a cgroup v2 environment.
smp_init() is called after the first two init functions. So we don't
have a complete list of active cpus and memory nodes until later in
cpuset_init_smp() which is the right time to set up effective_cpus
and effective_mems.
To fix this problem, the potentially incorrect cpus_allowed &
mems_allowed setup in cpuset_init_smp() are removed. For cgroup v2
systems, the initial cpuset_bind() call will set them up correctly.
For cgroup v1 systems, the second call to cpuset_bind() will do the
right setup.
cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 9390bfd9f1cd..6bd8f5ef40fe 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3390,8 +3390,9 @@ static struct notifier_block cpuset_track_online_nodes_nb = {
*/
void __init cpuset_init_smp(void)
{
- cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
- top_cpuset.mems_allowed = node_states[N_MEMORY];
cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
and only remove line
top_cpuset.mems_allowed = node_states[N_MEMORY];
?