diff options
Diffstat (limited to 'kernel/time/timer_migration.h')
| -rw-r--r-- | kernel/time/timer_migration.h | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h index 6c37d94a37d9..154accc7a543 100644 --- a/kernel/time/timer_migration.h +++ b/kernel/time/timer_migration.h @@ -22,7 +22,17 @@ struct tmigr_event { * struct tmigr_group - timer migration hierarchy group * @lock: Lock protecting the event information and group hierarchy * information during setup - * @parent: Pointer to the parent group + * @parent: Pointer to the parent group. Pointer is updated when a + * new hierarchy level is added because of a CPU coming + * online the first time. Once it is set, the pointer will + * not be removed or updated. When accessing parent pointer + * lock less to decide whether to abort a propagation or + * not, it is not a problem. The worst outcome is an + * unnecessary/early CPU wake up. But do not access parent + * pointer several times in the same 'action' (like + * activation, deactivation, check for remote expiry,...) + * without holding the lock as it is not ensured that value + * will not change. * @groupevt: Next event of the group which is only used when the * group is !active. The group event is then queued into * the parent timer queue. @@ -41,9 +51,8 @@ struct tmigr_event { * @num_children: Counter of group children to make sure the group is only * filled with TMIGR_CHILDREN_PER_GROUP; Required for setup * only - * @childmask: childmask of the group in the parent group; is set - * during setup and will never change; can be read - * lockless + * @groupmask: mask of the group in the parent group; is set during + * setup and will never change; can be read lockless * @list: List head that is added to the per level * tmigr_level_list; is required during setup when a * new group needs to be connected to the existing @@ -59,7 +68,7 @@ struct tmigr_group { unsigned int level; int numa_node; unsigned int num_children; - u8 childmask; + u8 groupmask; struct list_head list; }; @@ -79,7 +88,7 @@ struct tmigr_group { * hierarchy * @remote: Is set when timers of the CPU are expired remotely * @tmgroup: Pointer to the parent group - * @childmask: childmask of tmigr_cpu in the parent group + * @groupmask: mask of tmigr_cpu in the parent group * @wakeup: Stores the first timer when the timer migration * hierarchy is completely idle and remote expiry was done; * is returned to timer code in the idle path and is only @@ -92,7 +101,7 @@ struct tmigr_cpu { bool idle; bool remote; struct tmigr_group *tmgroup; - u8 childmask; + u8 groupmask; u64 wakeup; struct tmigr_event cpuevt; }; @@ -108,8 +117,8 @@ union tmigr_state { u32 state; /** * struct - split state of tmigr_group - * @active: Contains each childmask bit of the active children - * @migrator: Contains childmask of the child which is migrator + * @active: Contains each mask bit of the active children + * @migrator: Contains mask of the child which is migrator * @seq: Sequence counter needs to be increased when an update * to the tmigr_state is done. It prevents a race when * updates in the child groups are propagated in changed |