1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 #ifndef _KERNEL_TIME_MIGRATION_H 3 #define _KERNEL_TIME_MIGRATION_H 4 5 /* Per group capacity. Must be a power of 2! */ 6 #define TMIGR_CHILDREN_PER_GROUP 8 7 8 /** 9 * struct tmigr_event - a timer event associated to a CPU 10 * @nextevt: The node to enqueue an event in the parent group queue 11 * @cpu: The CPU to which this event belongs 12 * @ignore: Hint whether the event could be ignored; it is set when 13 * CPU or group is active; 14 */ 15 struct tmigr_event { 16 struct timerqueue_node nextevt; 17 unsigned int cpu; 18 bool ignore; 19 }; 20 21 /** 22 * struct tmigr_group - timer migration hierarchy group 23 * @lock: Lock protecting the event information and group hierarchy 24 * information during setup 25 * @parent: Pointer to the parent group 26 * @groupevt: Next event of the group which is only used when the 27 * group is !active. The group event is then queued into 28 * the parent timer queue. 29 * Ignore bit of @groupevt is set when the group is active. 30 * @next_expiry: Base monotonic expiry time of the next event of the 31 * group; It is used for the racy lockless check whether a 32 * remote expiry is required; it is always reliable 33 * @events: Timer queue for child events queued in the group 34 * @migr_state: State of the group (see union tmigr_state) 35 * @level: Hierarchy level of the group; Required during setup 36 * @numa_node: Required for setup only to make sure CPU and low level 37 * group information is NUMA local. It is set to NUMA node 38 * as long as the group level is per NUMA node (level < 39 * tmigr_crossnode_level); otherwise it is set to 40 * NUMA_NO_NODE 41 * @num_children: Counter of group children to make sure the group is only 42 * filled with TMIGR_CHILDREN_PER_GROUP; Required for setup 43 * only 44 * @childmask: childmask of the group in the parent group; is set 45 * during setup and will never change; can be read 46 * lockless 47 * @list: List head that is added to the per level 48 * tmigr_level_list; is required during setup when a 49 * new group needs to be connected to the existing 50 * hierarchy groups 51 */ 52 struct tmigr_group { 53 raw_spinlock_t lock; 54 struct tmigr_group *parent; 55 struct tmigr_event groupevt; 56 u64 next_expiry; 57 struct timerqueue_head events; 58 atomic_t migr_state; 59 unsigned int level; 60 int numa_node; 61 unsigned int num_children; 62 u8 childmask; 63 struct list_head list; 64 }; 65 66 /** 67 * struct tmigr_cpu - timer migration per CPU group 68 * @lock: Lock protecting the tmigr_cpu group information 69 * @online: Indicates whether the CPU is online; In deactivate path 70 * it is required to know whether the migrator in the top 71 * level group is to be set offline, while a timer is 72 * pending. Then another online CPU needs to be notified to 73 * take over the migrator role. Furthermore the information 74 * is required in CPU hotplug path as the CPU is able to go 75 * idle before the timer migration hierarchy hotplug AP is 76 * reached. During this phase, the CPU has to handle the 77 * global timers on its own and must not act as a migrator. 78 * @idle: Indicates whether the CPU is idle in the timer migration 79 * hierarchy 80 * @remote: Is set when timers of the CPU are expired remotely 81 * @tmgroup: Pointer to the parent group 82 * @childmask: childmask of tmigr_cpu in the parent group 83 * @wakeup: Stores the first timer when the timer migration 84 * hierarchy is completely idle and remote expiry was done; 85 * is returned to timer code in the idle path and is only 86 * used in idle path. 87 * @cpuevt: CPU event which could be enqueued into the parent group 88 */ 89 struct tmigr_cpu { 90 raw_spinlock_t lock; 91 bool online; 92 bool idle; 93 bool remote; 94 struct tmigr_group *tmgroup; 95 u8 childmask; 96 u64 wakeup; 97 struct tmigr_event cpuevt; 98 }; 99 100 /** 101 * union tmigr_state - state of tmigr_group 102 * @state: Combined version of the state - only used for atomic 103 * read/cmpxchg function 104 * @struct: Split version of the state - only use the struct members to 105 * update information to stay independent of endianness 106 */ 107 union tmigr_state { 108 u32 state; 109 /** 110 * struct - split state of tmigr_group 111 * @active: Contains each childmask bit of the active children 112 * @migrator: Contains childmask of the child which is migrator 113 * @seq: Sequence counter needs to be increased when an update 114 * to the tmigr_state is done. It prevents a race when 115 * updates in the child groups are propagated in changed 116 * order. Detailed information about the scenario is 117 * given in the documentation at the begin of 118 * timer_migration.c. 119 */ 120 struct { 121 u8 active; 122 u8 migrator; 123 u16 seq; 124 } __packed; 125 }; 126 127 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) 128 extern void tmigr_handle_remote(void); 129 extern bool tmigr_requires_handle_remote(void); 130 extern void tmigr_cpu_activate(void); 131 extern u64 tmigr_cpu_deactivate(u64 nextevt); 132 extern u64 tmigr_cpu_new_timer(u64 nextevt); 133 extern u64 tmigr_quick_check(u64 nextevt); 134 #else 135 static inline void tmigr_handle_remote(void) { } 136 static inline bool tmigr_requires_handle_remote(void) { return false; } 137 static inline void tmigr_cpu_activate(void) { } 138 #endif 139 140 #endif 141