From fae3fde65138b6071b1b0e0b567d4058a8b6a88c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 11 Jan 2016 15:00:50 +0100 Subject: [PATCH] perf: Collapse and fix event_function_call() users There is one common bug left in all the event_function_call() users, between loading ctx->task and getting to the remote_function(), ctx->task can already have been changed. Therefore we need to double check and retry if ctx->task != current. Insert another trampoline specific to event_function_call() that checks for this and further validates state. This also allows getting rid of the active/inactive functions. Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: David Ahern Cc: Jiri Olsa Cc: Linus Torvalds Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 2 +- kernel/events/core.c | 365 ++++++++++++++++------------------ kernel/events/hw_breakpoint.c | 2 +- 3 files changed, 168 insertions(+), 201 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index f9828a48f16a..6612732d8fd0 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1044,7 +1044,7 @@ extern void perf_swevent_put_recursion_context(int rctx); extern u64 perf_swevent_set_period(struct perf_event *event); extern void perf_event_enable(struct perf_event *event); extern void perf_event_disable(struct perf_event *event); -extern int __perf_event_disable(void *info); +extern void perf_event_disable_local(struct perf_event *event); extern void perf_event_task_tick(void); #else /* !CONFIG_PERF_EVENTS: */ static inline void * diff --git a/kernel/events/core.c b/kernel/events/core.c index 66c9ad4f8707..6620432491f6 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -126,6 +126,28 @@ static int cpu_function_call(int cpu, remote_function_f func, void *info) return data.ret; } +static inline struct perf_cpu_context * +__get_cpu_context(struct perf_event_context *ctx) +{ + return this_cpu_ptr(ctx->pmu->pmu_cpu_context); +} + +static void perf_ctx_lock(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx) +{ + raw_spin_lock(&cpuctx->ctx.lock); + if (ctx) + raw_spin_lock(&ctx->lock); +} + +static void perf_ctx_unlock(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx) +{ + if (ctx) + raw_spin_unlock(&ctx->lock); + raw_spin_unlock(&cpuctx->ctx.lock); +} + /* * On task ctx scheduling... * @@ -158,21 +180,96 @@ static int cpu_function_call(int cpu, remote_function_f func, void *info) * If ctx->nr_events, then ctx->is_active and cpuctx->task_ctx are set. */ -static void event_function_call(struct perf_event *event, - int (*active)(void *), - void (*inactive)(void *), - void *data) +typedef void (*event_f)(struct perf_event *, struct perf_cpu_context *, + struct perf_event_context *, void *); + +struct event_function_struct { + struct perf_event *event; + event_f func; + void *data; +}; + +static int event_function(void *info) +{ + struct event_function_struct *efs = info; + struct perf_event *event = efs->event; + struct perf_event_context *ctx = event->ctx; + struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + struct perf_event_context *task_ctx = cpuctx->task_ctx; + + WARN_ON_ONCE(!irqs_disabled()); + + /* + * Since we do the IPI call without holding ctx->lock things can have + * changed, double check we hit the task we set out to hit. + * + * If ctx->task == current, we know things must remain valid because + * we have IRQs disabled so we cannot schedule. + */ + if (ctx->task) { + if (ctx->task != current) + return -EAGAIN; + + WARN_ON_ONCE(task_ctx != ctx); + } else { + WARN_ON_ONCE(&cpuctx->ctx != ctx); + } + + perf_ctx_lock(cpuctx, task_ctx); + /* + * Now that we hold locks, double check state. Paranoia pays. + */ + if (task_ctx) { + WARN_ON_ONCE(task_ctx->task != current); + /* + * We only use event_function_call() on established contexts, + * and event_function() is only ever called when active (or + * rather, we'll have bailed in task_function_call() or the + * above ctx->task != current test), therefore we must have + * ctx->is_active here. + */ + WARN_ON_ONCE(!ctx->is_active); + /* + * And since we have ctx->is_active, cpuctx->task_ctx must + * match. + */ + WARN_ON_ONCE(cpuctx->task_ctx != task_ctx); + } + efs->func(event, cpuctx, ctx, efs->data); + perf_ctx_unlock(cpuctx, task_ctx); + + return 0; +} + +static void event_function_local(struct perf_event *event, event_f func, void *data) +{ + struct event_function_struct efs = { + .event = event, + .func = func, + .data = data, + }; + + int ret = event_function(&efs); + WARN_ON_ONCE(ret); +} + +static void event_function_call(struct perf_event *event, event_f func, void *data) { struct perf_event_context *ctx = event->ctx; struct task_struct *task = ctx->task; + struct event_function_struct efs = { + .event = event, + .func = func, + .data = data, + }; if (!task) { - cpu_function_call(event->cpu, active, data); + cpu_function_call(event->cpu, event_function, &efs); return; } again: - if (!task_function_call(task, active, data)) + if (!task_function_call(task, event_function, &efs)) return; raw_spin_lock_irq(&ctx->lock); @@ -185,7 +282,7 @@ again: raw_spin_unlock_irq(&ctx->lock); goto again; } - inactive(data); + func(event, NULL, ctx, data); raw_spin_unlock_irq(&ctx->lock); } @@ -400,28 +497,6 @@ static inline u64 perf_event_clock(struct perf_event *event) return event->clock(); } -static inline struct perf_cpu_context * -__get_cpu_context(struct perf_event_context *ctx) -{ - return this_cpu_ptr(ctx->pmu->pmu_cpu_context); -} - -static void perf_ctx_lock(struct perf_cpu_context *cpuctx, - struct perf_event_context *ctx) -{ - raw_spin_lock(&cpuctx->ctx.lock); - if (ctx) - raw_spin_lock(&ctx->lock); -} - -static void perf_ctx_unlock(struct perf_cpu_context *cpuctx, - struct perf_event_context *ctx) -{ - if (ctx) - raw_spin_unlock(&ctx->lock); - raw_spin_unlock(&cpuctx->ctx.lock); -} - #ifdef CONFIG_CGROUP_PERF static inline bool @@ -1684,38 +1759,22 @@ group_sched_out(struct perf_event *group_event, cpuctx->exclusive = 0; } -struct remove_event { - struct perf_event *event; - bool detach_group; -}; - -static void ___perf_remove_from_context(void *info) -{ - struct remove_event *re = info; - struct perf_event *event = re->event; - struct perf_event_context *ctx = event->ctx; - - if (re->detach_group) - perf_group_detach(event); - list_del_event(event, ctx); -} - /* * Cross CPU call to remove a performance event * * We disable the event on the hardware level first. After that we * remove it from the context list. */ -static int __perf_remove_from_context(void *info) +static void +__perf_remove_from_context(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct remove_event *re = info; - struct perf_event *event = re->event; - struct perf_event_context *ctx = event->ctx; - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + bool detach_group = (unsigned long)info; - raw_spin_lock(&ctx->lock); event_sched_out(event, cpuctx, ctx); - if (re->detach_group) + if (detach_group) perf_group_detach(event); list_del_event(event, ctx); @@ -1726,17 +1785,11 @@ static int __perf_remove_from_context(void *info) cpuctx->task_ctx = NULL; } } - raw_spin_unlock(&ctx->lock); - - return 0; } /* * Remove the event from a task's (or a CPU's) list of events. * - * CPU events are removed with a smp call. For task events we only - * call when the task is on a CPU. - * * If event->ctx is a cloned context, callers must make sure that * every task struct that event->ctx->task could possibly point to * remains valid. This is OK when called from perf_release since @@ -1746,71 +1799,31 @@ static int __perf_remove_from_context(void *info) */ static void perf_remove_from_context(struct perf_event *event, bool detach_group) { - struct perf_event_context *ctx = event->ctx; - struct remove_event re = { - .event = event, - .detach_group = detach_group, - }; - - lockdep_assert_held(&ctx->mutex); + lockdep_assert_held(&event->ctx->mutex); event_function_call(event, __perf_remove_from_context, - ___perf_remove_from_context, &re); + (void *)(unsigned long)detach_group); } /* * Cross CPU call to disable a performance event */ -int __perf_event_disable(void *info) +static void __perf_event_disable(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct perf_event *event = info; - struct perf_event_context *ctx = event->ctx; - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + if (event->state < PERF_EVENT_STATE_INACTIVE) + return; - /* - * If this is a per-task event, need to check whether this - * event's task is the current task on this cpu. - * - * Can trigger due to concurrent perf_event_context_sched_out() - * flipping contexts around. - */ - if (ctx->task && cpuctx->task_ctx != ctx) - return -EINVAL; - - raw_spin_lock(&ctx->lock); - - /* - * If the event is on, turn it off. - * If it is in error state, leave it in error state. - */ - if (event->state >= PERF_EVENT_STATE_INACTIVE) { - update_context_time(ctx); - update_cgrp_time_from_event(event); - update_group_times(event); - if (event == event->group_leader) - group_sched_out(event, cpuctx, ctx); - else - event_sched_out(event, cpuctx, ctx); - event->state = PERF_EVENT_STATE_OFF; - } - - raw_spin_unlock(&ctx->lock); - - return 0; -} - -void ___perf_event_disable(void *info) -{ - struct perf_event *event = info; - - /* - * Since we have the lock this context can't be scheduled - * in, so we can change the state safely. - */ - if (event->state == PERF_EVENT_STATE_INACTIVE) { - update_group_times(event); - event->state = PERF_EVENT_STATE_OFF; - } + update_context_time(ctx); + update_cgrp_time_from_event(event); + update_group_times(event); + if (event == event->group_leader) + group_sched_out(event, cpuctx, ctx); + else + event_sched_out(event, cpuctx, ctx); + event->state = PERF_EVENT_STATE_OFF; } /* @@ -1837,8 +1850,12 @@ static void _perf_event_disable(struct perf_event *event) } raw_spin_unlock_irq(&ctx->lock); - event_function_call(event, __perf_event_disable, - ___perf_event_disable, event); + event_function_call(event, __perf_event_disable, NULL); +} + +void perf_event_disable_local(struct perf_event *event) +{ + event_function_local(event, __perf_event_disable, NULL); } /* @@ -2202,44 +2219,29 @@ static void __perf_event_mark_enabled(struct perf_event *event) /* * Cross CPU call to enable a performance event */ -static int __perf_event_enable(void *info) +static void __perf_event_enable(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct perf_event *event = info; - struct perf_event_context *ctx = event->ctx; struct perf_event *leader = event->group_leader; - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); - struct perf_event_context *task_ctx = cpuctx->task_ctx; - - /* - * There's a time window between 'ctx->is_active' check - * in perf_event_enable function and this place having: - * - IRQs on - * - ctx->lock unlocked - * - * where the task could be killed and 'ctx' deactivated - * by perf_event_exit_task. - */ - if (!ctx->is_active) - return -EINVAL; - - perf_ctx_lock(cpuctx, task_ctx); - WARN_ON_ONCE(&cpuctx->ctx != ctx && task_ctx != ctx); - update_context_time(ctx); + struct perf_event_context *task_ctx; if (event->state >= PERF_EVENT_STATE_INACTIVE) - goto unlock; - - /* - * set current task's cgroup time reference point - */ - perf_cgroup_set_timestamp(current, ctx); + return; + update_context_time(ctx); __perf_event_mark_enabled(event); + if (!ctx->is_active) + return; + if (!event_filter_match(event)) { - if (is_cgroup_event(event)) + if (is_cgroup_event(event)) { + perf_cgroup_set_timestamp(current, ctx); // XXX ? perf_cgroup_defer_enabled(event); - goto unlock; + } + return; } /* @@ -2247,19 +2249,13 @@ static int __perf_event_enable(void *info) * then don't put it on unless the group is on. */ if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) - goto unlock; + return; + + task_ctx = cpuctx->task_ctx; + if (ctx->task) + WARN_ON_ONCE(task_ctx != ctx); ctx_resched(cpuctx, task_ctx); - -unlock: - perf_ctx_unlock(cpuctx, task_ctx); - - return 0; -} - -void ___perf_event_enable(void *info) -{ - __perf_event_mark_enabled((struct perf_event *)info); } /* @@ -2292,8 +2288,7 @@ static void _perf_event_enable(struct perf_event *event) event->state = PERF_EVENT_STATE_OFF; raw_spin_unlock_irq(&ctx->lock); - event_function_call(event, __perf_event_enable, - ___perf_event_enable, event); + event_function_call(event, __perf_event_enable, NULL); } /* @@ -4095,36 +4090,14 @@ static void perf_event_for_each(struct perf_event *event, perf_event_for_each_child(sibling, func); } -struct period_event { - struct perf_event *event; - u64 value; -}; - -static void ___perf_event_period(void *info) +static void __perf_event_period(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct period_event *pe = info; - struct perf_event *event = pe->event; - u64 value = pe->value; - - if (event->attr.freq) { - event->attr.sample_freq = value; - } else { - event->attr.sample_period = value; - event->hw.sample_period = value; - } - - local64_set(&event->hw.period_left, 0); -} - -static int __perf_event_period(void *info) -{ - struct period_event *pe = info; - struct perf_event *event = pe->event; - struct perf_event_context *ctx = event->ctx; - u64 value = pe->value; + u64 value = *((u64 *)info); bool active; - raw_spin_lock(&ctx->lock); if (event->attr.freq) { event->attr.sample_freq = value; } else { @@ -4144,14 +4117,10 @@ static int __perf_event_period(void *info) event->pmu->start(event, PERF_EF_RELOAD); perf_pmu_enable(ctx->pmu); } - raw_spin_unlock(&ctx->lock); - - return 0; } static int perf_event_period(struct perf_event *event, u64 __user *arg) { - struct period_event pe = { .event = event, }; u64 value; if (!is_sampling_event(event)) @@ -4166,10 +4135,7 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg) if (event->attr.freq && value > sysctl_perf_event_sample_rate) return -EINVAL; - pe.value = value; - - event_function_call(event, __perf_event_period, - ___perf_event_period, &pe); + event_function_call(event, __perf_event_period, &value); return 0; } @@ -4941,7 +4907,7 @@ static void perf_pending_event(struct irq_work *entry) if (event->pending_disable) { event->pending_disable = 0; - __perf_event_disable(event); + perf_event_disable_local(event); } if (event->pending_wakeup) { @@ -9239,13 +9205,14 @@ static void perf_event_init_cpu(int cpu) #if defined CONFIG_HOTPLUG_CPU || defined CONFIG_KEXEC_CORE static void __perf_event_exit_context(void *__info) { - struct remove_event re = { .detach_group = true }; struct perf_event_context *ctx = __info; + struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + struct perf_event *event; - rcu_read_lock(); - list_for_each_entry_rcu(re.event, &ctx->event_list, event_entry) - __perf_remove_from_context(&re); - rcu_read_unlock(); + raw_spin_lock(&ctx->lock); + list_for_each_entry(event, &ctx->event_list, event_entry) + __perf_remove_from_context(event, cpuctx, ctx, (void *)(unsigned long)true); + raw_spin_unlock(&ctx->lock); } static void perf_event_exit_cpu_context(int cpu) diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index 92ce5f4ccc26..3f8cb1e14588 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -444,7 +444,7 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att * current task. */ if (irqs_disabled() && bp->ctx && bp->ctx->task == current) - __perf_event_disable(bp); + perf_event_disable_local(bp); else perf_event_disable(bp);