diff options
Diffstat (limited to 'kernel')
44 files changed, 2274 insertions, 996 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index e24aa3241387..43f95d190eea 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1845,7 +1845,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz union bpf_attr attr = {}; int err; - if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled) + if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; err = check_uarg_tail_zero(uattr, sizeof(attr), size); diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 8cda3bc3ae22..4bfb2908ec15 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -3183,6 +3183,16 @@ static int cgroup_enable_threaded(struct cgroup *cgrp) if (cgroup_is_threaded(cgrp)) return 0; + /* + * If @cgroup is populated or has domain controllers enabled, it + * can't be switched. While the below cgroup_can_be_thread_root() + * test can catch the same conditions, that's only when @parent is + * not mixable, so let's check it explicitly. + */ + if (cgroup_is_populated(cgrp) || + cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask) + return -EOPNOTSUPP; + /* we're joining the parent's domain, ensure its validity */ if (!cgroup_is_valid_domain(dom_cgrp) || !cgroup_can_be_thread_root(dom_cgrp)) diff --git a/kernel/compat.c b/kernel/compat.c index 3247fe761f60..3f5fa8902e7d 100644 --- a/kernel/compat.c +++ b/kernel/compat.c @@ -488,25 +488,6 @@ get_compat_sigset(sigset_t *set, const compat_sigset_t __user *compat) } EXPORT_SYMBOL_GPL(get_compat_sigset); -int -put_compat_sigset(compat_sigset_t __user *compat, const sigset_t *set, - unsigned int size) -{ - /* size <= sizeof(compat_sigset_t) <= sizeof(sigset_t) */ -#ifdef __BIG_ENDIAN - compat_sigset_t v; - switch (_NSIG_WORDS) { - case 4: v.sig[7] = (set->sig[3] >> 32); v.sig[6] = set->sig[3]; - case 3: v.sig[5] = (set->sig[2] >> 32); v.sig[4] = set->sig[2]; - case 2: v.sig[3] = (set->sig[1] >> 32); v.sig[2] = set->sig[1]; - case 1: v.sig[1] = (set->sig[0] >> 32); v.sig[0] = set->sig[0]; - } - return copy_to_user(compat, &v, size) ? -EFAULT : 0; -#else - return copy_to_user(compat, set, size) ? -EFAULT : 0; -#endif -} - #ifdef CONFIG_NUMA COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages, compat_uptr_t __user *, pages32, diff --git a/kernel/cpu.c b/kernel/cpu.c index 53f7dc65f9a3..0db8938fbb23 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -124,24 +124,11 @@ struct cpuhp_step { }; static DEFINE_MUTEX(cpuhp_state_mutex); -static struct cpuhp_step cpuhp_bp_states[]; -static struct cpuhp_step cpuhp_ap_states[]; - -static bool cpuhp_is_ap_state(enum cpuhp_state state) -{ - /* - * The extra check for CPUHP_TEARDOWN_CPU is only for documentation - * purposes as that state is handled explicitly in cpu_down. - */ - return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU; -} +static struct cpuhp_step cpuhp_hp_states[]; static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state) { - struct cpuhp_step *sp; - - sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states; - return sp + state; + return cpuhp_hp_states + state; } /** @@ -239,6 +226,15 @@ err: } #ifdef CONFIG_SMP +static bool cpuhp_is_ap_state(enum cpuhp_state state) +{ + /* + * The extra check for CPUHP_TEARDOWN_CPU is only for documentation + * purposes as that state is handled explicitly in cpu_down. + */ + return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU; +} + static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup) { struct completion *done = bringup ? &st->done_up : &st->done_down; @@ -1224,7 +1220,7 @@ int __boot_cpu_id; #endif /* CONFIG_SMP */ /* Boot processor state steps */ -static struct cpuhp_step cpuhp_bp_states[] = { +static struct cpuhp_step cpuhp_hp_states[] = { [CPUHP_OFFLINE] = { .name = "offline", .startup.single = NULL, @@ -1289,24 +1285,6 @@ static struct cpuhp_step cpuhp_bp_states[] = { .teardown.single = NULL, .cant_stop = true, }, - /* - * Handled on controll processor until the plugged processor manages - * this itself. - */ - [CPUHP_TEARDOWN_CPU] = { - .name = "cpu:teardown", - .startup.single = NULL, - .teardown.single = takedown_cpu, - .cant_stop = true, - }, -#else - [CPUHP_BRINGUP_CPU] = { }, -#endif -}; - -/* Application processor state steps */ -static struct cpuhp_step cpuhp_ap_states[] = { -#ifdef CONFIG_SMP /* Final state before CPU kills itself */ [CPUHP_AP_IDLE_DEAD] = { .name = "idle:dead", @@ -1340,6 +1318,16 @@ static struct cpuhp_step cpuhp_ap_states[] = { [CPUHP_AP_ONLINE] = { .name = "ap:online", }, + /* + * Handled on controll processor until the plugged processor manages + * this itself. + */ + [CPUHP_TEARDOWN_CPU] = { + .name = "cpu:teardown", + .startup.single = NULL, + .teardown.single = takedown_cpu, + .cant_stop = true, + }, /* Handle smpboot threads park/unpark */ [CPUHP_AP_SMPBOOT_THREADS] = { .name = "smpboot/threads:online", @@ -1408,11 +1396,11 @@ static int cpuhp_reserve_state(enum cpuhp_state state) switch (state) { case CPUHP_AP_ONLINE_DYN: - step = cpuhp_ap_states + CPUHP_AP_ONLINE_DYN; + step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN; end = CPUHP_AP_ONLINE_DYN_END; break; case CPUHP_BP_PREPARE_DYN: - step = cpuhp_bp_states + CPUHP_BP_PREPARE_DYN; + step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN; end = CPUHP_BP_PREPARE_DYN_END; break; default: diff --git a/kernel/events/core.c b/kernel/events/core.c index 96db9ae5d5af..fc1c330c6bd6 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -430,7 +430,7 @@ static void update_perf_cpu_limits(void) WRITE_ONCE(perf_sample_allowed_ns, tmp); } -static int perf_rotate_context(struct perf_cpu_context *cpuctx); +static bool perf_rotate_context(struct perf_cpu_context *cpuctx); int perf_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, @@ -643,7 +643,7 @@ static void perf_event_update_sibling_time(struct perf_event *leader) { struct perf_event *sibling; - list_for_each_entry(sibling, &leader->sibling_list, group_entry) + for_each_sibling_event(sibling, leader) perf_event_update_time(sibling); } @@ -724,9 +724,15 @@ static inline void __update_cgrp_time(struct perf_cgroup *cgrp) static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx) { - struct perf_cgroup *cgrp_out = cpuctx->cgrp; - if (cgrp_out) - __update_cgrp_time(cgrp_out); + struct perf_cgroup *cgrp = cpuctx->cgrp; + struct cgroup_subsys_state *css; + + if (cgrp) { + for (css = &cgrp->css; css; css = css->parent) { + cgrp = container_of(css, struct perf_cgroup, css); + __update_cgrp_time(cgrp); + } + } } static inline void update_cgrp_time_from_event(struct perf_event *event) @@ -754,6 +760,7 @@ perf_cgroup_set_timestamp(struct task_struct *task, { struct perf_cgroup *cgrp; struct perf_cgroup_info *info; + struct cgroup_subsys_state *css; /* * ctx->lock held by caller @@ -764,8 +771,12 @@ perf_cgroup_set_timestamp(struct task_struct *task, return; cgrp = perf_cgroup_from_task(task, ctx); - info = this_cpu_ptr(cgrp->info); - info->timestamp = ctx->timestamp; + + for (css = &cgrp->css; css; css = css->parent) { + cgrp = container_of(css, struct perf_cgroup, css); + info = this_cpu_ptr(cgrp->info); + info->timestamp = ctx->timestamp; + } } static DEFINE_PER_CPU(struct list_head, cgrp_cpuctx_list); @@ -937,27 +948,39 @@ list_update_cgroup_event(struct perf_event *event, if (!is_cgroup_event(event)) return; - if (add && ctx->nr_cgroups++) - return; - else if (!add && --ctx->nr_cgroups) - return; /* * Because cgroup events are always per-cpu events, * this will always be called from the right CPU. */ cpuctx = __get_cpu_context(ctx); - cpuctx_entry = &cpuctx->cgrp_cpuctx_entry; - /* cpuctx->cgrp is NULL unless a cgroup event is active in this CPU .*/ - if (add) { + + /* + * Since setting cpuctx->cgrp is conditional on the current @cgrp + * matching the event's cgroup, we must do this for every new event, + * because if the first would mismatch, the second would not try again + * and we would leave cpuctx->cgrp unset. + */ + if (add && !cpuctx->cgrp) { struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx); - list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list)); if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup)) cpuctx->cgrp = cgrp; - } else { - list_del(cpuctx_entry); - cpuctx->cgrp = NULL; } + + if (add && ctx->nr_cgroups++) + return; + else if (!add && --ctx->nr_cgroups) + return; + + /* no cgroup running */ + if (!add) + cpuctx->cgrp = NULL; + + cpuctx_entry = &cpuctx->cgrp_cpuctx_entry; + if (add) + list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list)); + else + list_del(cpuctx_entry); } #else /* !CONFIG_CGROUP_PERF */ @@ -1041,7 +1064,7 @@ list_update_cgroup_event(struct perf_event *event, static enum hrtimer_restart perf_mux_hrtimer_handler(struct hrtimer *hr) { struct perf_cpu_context *cpuctx; - int rotations = 0; + bool rotations; lockdep_assert_irqs_disabled(); @@ -1460,8 +1483,21 @@ static enum event_type_t get_event_type(struct perf_event *event) return event_type; } -static struct list_head * -ctx_group_list(struct perf_event *event, struct perf_event_context *ctx) +/* + * Helper function to initialize event group nodes. + */ +static void init_event_group(struct perf_event *event) +{ + RB_CLEAR_NODE(&event->group_node); + event->group_index = 0; +} + +/* + * Extract pinned or flexible groups from the context + * based on event attrs bits. + */ +static struct perf_event_groups * +get_event_groups(struct perf_event *event, struct perf_event_context *ctx) { if (event->attr.pinned) return &ctx->pinned_groups; @@ -1470,6 +1506,156 @@ ctx_group_list(struct perf_event *event, struct perf_event_context *ctx) } /* + * Helper function to initializes perf_event_group trees. + */ +static void perf_event_groups_init(struct perf_event_groups *groups) +{ + groups->tree = RB_ROOT; + groups->index = 0; +} + +/* + * Compare function for event groups; + * + * Implements complex key that first sorts by CPU and then by virtual index + * which provides ordering when rotating groups for the same CPU. + */ +static bool +perf_event_groups_less(struct perf_event *left, struct perf_event *right) +{ + if (left->cpu < right->cpu) + return true; + if (left->cpu > right->cpu) + return false; + + if (left->group_index < right->group_index) + return true; + if (left->group_index > right->group_index) + return false; + + return false; +} + +/* + * Insert @event into @groups' tree; using {@event->cpu, ++@groups->index} for + * key (see perf_event_groups_less). This places it last inside the CPU + * subtree. + */ +static void +perf_event_groups_insert(struct perf_event_groups *groups, + struct perf_event *event) +{ + struct perf_event *node_event; + struct rb_node *parent; + struct rb_node **node; + + event->group_index = ++groups->index; + + node = &groups->tree.rb_node; + parent = *node; + + while (*node) { + parent = *node; + node_event = container_of(*node, struct perf_event, group_node); + + if (perf_event_groups_less(event, node_event)) + node = &parent->rb_left; + else + node = &parent->rb_right; + } + + rb_link_node(&event->group_node, parent, node); + rb_insert_color(&event->group_node, &groups->tree); +} + +/* + * Helper function to insert event into the pinned or flexible groups. + */ +static void +add_event_to_groups(struct perf_event *event, struct perf_event_context *ctx) +{ + struct perf_event_groups *groups; + + groups = get_event_groups(event, ctx); + perf_event_groups_insert(groups, event); +} + +/* + * Delete a group from a tree. + */ +static void +perf_event_groups_delete(struct perf_event_groups *groups, + struct perf_event *event) +{ + WARN_ON_ONCE(RB_EMPTY_NODE(&event->group_node) || + RB_EMPTY_ROOT(&groups->tree)); + + rb_erase(&event->group_node, &groups->tree); + init_event_group(event); +} + +/* + * Helper function to delete event from its groups. + */ +static void +del_event_from_groups(struct perf_event *event, struct perf_event_context *ctx) +{ + struct perf_event_groups *groups; + + groups = get_event_groups(event, ctx); + perf_event_groups_delete(groups, event); +} + +/* + * Get the leftmost event in the @cpu subtree. + */ +static struct perf_event * +perf_event_groups_first(struct perf_event_groups *groups, int cpu) +{ + struct perf_event *node_event = NULL, *match = NULL; + struct rb_node *node = groups->tree.rb_node; + + while (node) { + node_event = container_of(node, struct perf_event, group_node); + + if (cpu < node_event->cpu) { + node = node->rb_left; + } else if (cpu > node_event->cpu) { + node = node->rb_right; + } else { + match = node_event; + node = node->rb_left; + } + } + + return match; +} + +/* + * Like rb_entry_next_safe() for the @cpu subtree. + */ +static struct perf_event * +perf_event_groups_next(struct perf_event *event) +{ + struct perf_event *next; + + next = rb_entry_safe(rb_next(&event->group_node), typeof(*event), group_node); + if (next && next->cpu == event->cpu) + return next; + + return NULL; +} + +/* + * Iterate through the whole groups tree. + */ +#define perf_event_groups_for_each(event, groups) \ + for (event = rb_entry_safe(rb_first(&((groups)->tree)), \ + typeof(*event), group_node); event; \ + event = rb_entry_safe(rb_next(&event->group_node), \ + typeof(*event), group_node)) + +/* * Add a event from the lists for its context. * Must be called with ctx->mutex and ctx->lock held. */ @@ -1489,12 +1675,8 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx) * perf_group_detach can, at all times, locate all siblings. */ if (event->group_leader == event) { - struct list_head *list; - event->group_caps = event->event_caps; - - list = ctx_group_list(event, ctx); - list_add_tail(&event->group_entry, list); + add_event_to_groups(event, ctx); } list_update_cgroup_event(event, ctx, true); @@ -1652,12 +1834,12 @@ static void perf_group_attach(struct perf_event *event) group_leader->group_caps &= event->event_caps; - list_add_tail(&event->group_entry, &group_leader->sibling_list); + list_add_tail(&event->sibling_list, &group_leader->sibling_list); group_leader->nr_siblings++; perf_event__header_size(group_leader); - list_for_each_entry(pos, &group_leader->sibling_list, group_entry) + for_each_sibling_event(pos, group_leader) perf_event__header_size(pos); } @@ -1688,7 +1870,7 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) list_del_rcu(&event->event_entry); if (event->group_leader == event) - list_del_init(&event->group_entry); + del_event_from_groups(event, ctx); /* * If event was in error state, then keep it @@ -1706,9 +1888,9 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) static void perf_group_detach(struct perf_event *event) { struct perf_event *sibling, *tmp; - struct list_head *list = NULL; + struct perf_event_context *ctx = event->ctx; - lockdep_assert_held(&event->ctx->lock); + lockdep_assert_held(&ctx->lock); /* * We can have double detach due to exit/hot-unplug + close. @@ -1722,34 +1904,42 @@ static void perf_group_detach(struct perf_event *event) * If this is a sibling, remove it from its group. */ if (event->group_leader != event) { - list_del_init(&event->group_entry); + list_del_init(&event->sibling_list); event->group_leader->nr_siblings--; goto out; } - if (!list_empty(&event->group_entry)) - list = &event->group_entry; - /* * If this was a group event with sibling events then * upgrade the siblings to singleton events by adding them * to whatever list we are on. */ - list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) { - if (list) - list_move_tail(&sibling->group_entry, list); + list_for_each_entry_safe(sibling, tmp, &event->sibling_list, sibling_list) { + sibling->group_leader = sibling; + list_del_init(&sibling->sibling_list); /* Inherit group flags from the previous leader */ sibling->group_caps = event->group_caps; + if (!RB_EMPTY_NODE(&event->group_node)) { + add_event_to_groups(sibling, event->ctx); + + if (sibling->state == PERF_EVENT_STATE_ACTIVE) { + struct list_head *list = sibling->attr.pinned ? + &ctx->pinned_active : &ctx->flexible_active; + + list_add_tail(&sibling->active_list, list); + } + } + WARN_ON_ONCE(sibling->ctx != event->ctx); } out: perf_event__header_size(event->group_leader); - list_for_each_entry(tmp, &event->group_leader->sibling_list, group_entry) + for_each_sibling_event(tmp, event->group_leader) perf_event__header_size(tmp); } @@ -1772,13 +1962,13 @@ static inline int __pmu_filter_match(struct perf_event *event) */ static inline int pmu_filter_match(struct perf_event *event) { - struct perf_event *child; + struct perf_event *sibling; if (!__pmu_filter_match(event)) return 0; - list_for_each_entry(child, &event->sibling_list, group_entry) { - if (!__pmu_filter_match(child)) + for_each_sibling_event(sibling, event) { + if (!__pmu_filter_match(sibling)) return 0; } @@ -1805,6 +1995,13 @@ event_sched_out(struct perf_event *event, if (event->state != PERF_EVENT_STATE_ACTIVE) return; + /* + * Asymmetry; we only schedule events _IN_ through ctx_sched_in(), but + * we can schedule events _OUT_ individually through things like + * __perf_remove_from_context(). + */ + list_del_init(&event->active_list); + perf_pmu_disable(event->pmu); event->pmu->del(event, 0); @@ -1845,7 +2042,7 @@ group_sched_out(struct perf_event *group_event, /* * Schedule out siblings (if any): */ - list_for_each_entry(event, &group_event->sibling_list, group_entry) + for_each_sibling_event(event, group_event) event_sched_out(event, cpuctx, ctx); perf_pmu_enable(ctx->pmu); @@ -2124,7 +2321,7 @@ group_sched_in(struct perf_event *group_event, /* * Schedule in siblings as one group (if any): */ - list_for_each_entry(event, &group_event->sibling_list, group_entry) { + for_each_sibling_event(event, group_event) { if (event_sched_in(event, cpuctx, ctx)) { partial_group = event; goto group_error; @@ -2140,7 +2337,7 @@ group_error: * partial group before returning: * The events up to the failed event are scheduled out normally. */ - list_for_each_entry(event, &group_event->sibling_list, group_entry) { + for_each_sibling_event(event, group_event) { if (event == partial_group) break; @@ -2246,7 +2443,7 @@ static void ctx_resched(struct perf_cpu_context *cpuctx, struct perf_event_context *task_ctx, enum event_type_t event_type) { - enum event_type_t ctx_event_type = event_type & EVENT_ALL; + enum event_type_t ctx_event_type; bool cpu_event = !!(event_type & EVENT_CPU); /* @@ -2256,6 +2453,8 @@ static void ctx_resched(struct perf_cpu_context *cpuctx, if (event_type & EVENT_PINNED) event_type |= EVENT_FLEXIBLE; + ctx_event_type = event_type & EVENT_ALL; + perf_pmu_disable(cpuctx->ctx.pmu); if (task_ctx) task_ctx_sched_out(cpuctx, task_ctx, event_type); @@ -2315,6 +2514,18 @@ static int __perf_install_in_context(void *info) raw_spin_lock(&task_ctx->lock); } +#ifdef CONFIG_CGROUP_PERF + if (is_cgroup_event(event)) { + /* + * If the current cgroup doesn't match the event's + * cgroup, we should not try to schedule it. + */ + struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx); + reprogram = cgroup_is_descendant(cgrp->css.cgroup, + event->cgrp->css.cgroup); + } +#endif + if (reprogram) { ctx_sched_out(ctx, cpuctx, EVENT_TIME); add_event_to_ctx(event, ctx); @@ -2648,12 +2859,47 @@ int perf_event_refresh(struct perf_event *event, int refresh) } EXPORT_SYMBOL_GPL(perf_event_refresh); +static int perf_event_modify_breakpoint(struct perf_event *bp, + struct perf_event_attr *attr) +{ + int err; + + _perf_event_disable(bp); + + err = modify_user_hw_breakpoint_check(bp, attr, true); + if (err) { + if (!bp->attr.disabled) + _perf_event_enable(bp); + + return err; + } + + if (!attr->disabled) + _perf_event_enable(bp); + return 0; +} + +static int perf_event_modify_attr(struct perf_event *event, + struct perf_event_attr *attr) +{ + if (event->attr.type != attr->type) + return -EINVAL; + + switch (event->attr.type) { + case PERF_TYPE_BREAKPOINT: + return perf_event_modify_breakpoint(event, attr); + default: + /* Place holder for future additions. */ + return -EOPNOTSUPP; + } +} + static void ctx_sched_out(struct perf_event_context *ctx, struct perf_cpu_context *cpuctx, enum event_type_t event_type) { + struct perf_event *event, *tmp; int is_active = ctx->is_active; - struct perf_event *event; lockdep_assert_held(&ctx->lock); @@ -2700,12 +2946,12 @@ static void ctx_sched_out(struct perf_event_context *ctx, perf_pmu_disable(ctx->pmu); if (is_active & EVENT_PINNED) { - list_for_each_entry(event, &ctx->pinned_groups, group_entry) + list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list) group_sched_out(event, cpuctx, ctx); } if (is_active & EVENT_FLEXIBLE) { - list_for_each_entry(event, &ctx->flexible_groups, group_entry) + list_for_each_entry_safe(event, tmp, &ctx->flexible_active, active_list) group_sched_out(event, cpuctx, ctx); } perf_pmu_enable(ctx->pmu); @@ -2992,53 +3238,116 @@ static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx, ctx_sched_out(&cpuctx->ctx, cpuctx, event_type); } -static void -ctx_pinned_sched_in(struct perf_event_context *ctx, - struct perf_cpu_context *cpuctx) +static int visit_groups_merge(struct perf_event_groups *groups, int cpu, + int (*func)(struct perf_event *, void *), void *data) { - struct perf_event *event; + struct perf_event **evt, *evt1, *evt2; + int ret; - list_for_each_entry(event, &ctx->pinned_groups, group_entry) { - if (event->state <= PERF_EVENT_STATE_OFF) - continue; - if (!event_filter_match(event)) - continue; + evt1 = perf_event_groups_first(groups, -1); + evt2 = perf_event_groups_first(groups, cpu); + |