On 4/25/22 03:30, Feng Tang wrote:
Hi Waiman,
Thanks for the patch!
On Sun, Apr 24, 2022 at 10:09:26PM -0400, Waiman Long wrote:
There are 3 places where the cpu and node masks of the top cpuset can be initialized in the order they are executed:
- start_kernel -> cpuset_init()
- start_kernel -> cgroup_init() -> cpuset_bind()
- 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 assuming that effective_mems and effective_cpus have been set up properly which is not strictly the case here. As a result, cpu and memory node hot add may fail to update the cpu and node masks of the top cpuset to include the newly added cpu or node in a cgroup v2 environment.
To fix this problem, the redundant cpus_allowed and mems_allowed mask setup in cpuset_init_smp() are removed. The effective_cpus and effective_mems setup there are moved to cpuset_bind().
cc: stable@vger.kernel.org Signed-off-by: Waiman Long longman@redhat.com
kernel/cgroup/cpuset.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 9390bfd9f1cd..a2e15a43397e 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2961,6 +2961,9 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css) percpu_down_write(&cpuset_rwsem); spin_lock_irq(&callback_lock);
- cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
- top_cpuset.effective_mems = node_states[N_MEMORY];
- if (is_in_v2_mode()) { cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask); top_cpuset.mems_allowed = node_possible_map;
@@ -3390,13 +3393,6 @@ 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];
- top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
- cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
- top_cpuset.effective_mems = node_states[N_MEMORY];
IIUC, the init order is: cpuset_bind() smp_init() cpuset_init_smp()
while all cpus except boot cpu is brought up in smp_init(), so I'm thinking moving the cpus_allowed init from cpuset_init_smp() to cpuset_bind() may cause some problem.
Good point. So cpuset_init_smp() is still useful for setting the right effective_cpus and probably effective_mems. I will update the patch accordingly.
Thanks, Longman
Thanks, Feng