diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/perf_event.c | 46 |
1 files changed, 27 insertions, 19 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 84522c79698..126a302c481 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -2201,13 +2201,6 @@ find_lively_task_by_vpid(pid_t vpid) if (!task) return ERR_PTR(-ESRCH); - /* - * Can't attach events to a dying task. - */ - err = -ESRCH; - if (task->flags & PF_EXITING) - goto errout; - /* Reuse ptrace permission checks for now. */ err = -EACCES; if (!ptrace_may_access(task, PTRACE_MODE_READ)) @@ -2268,14 +2261,27 @@ retry: get_ctx(ctx); - if (cmpxchg(&task->perf_event_ctxp[ctxn], NULL, ctx)) { - /* - * We raced with some other task; use - * the context they set. - */ + err = 0; + mutex_lock(&task->perf_event_mutex); + /* + * If it has already passed perf_event_exit_task(). + * we must see PF_EXITING, it takes this mutex too. + */ + if (task->flags & PF_EXITING) + err = -ESRCH; + else if (task->perf_event_ctxp[ctxn]) + err = -EAGAIN; + else + rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx); + mutex_unlock(&task->perf_event_mutex); + + if (unlikely(err)) { put_task_struct(task); kfree(ctx); - goto retry; + + if (err == -EAGAIN) + goto retry; + goto errout; } } @@ -5374,6 +5380,8 @@ free_dev: goto out; } +static struct lock_class_key cpuctx_mutex; + int perf_pmu_register(struct pmu *pmu, char *name, int type) { int cpu, ret; @@ -5422,6 +5430,7 @@ skip_type: cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu); __perf_event_init_context(&cpuctx->ctx); + lockdep_set_class(&cpuctx->ctx.mutex, &cpuctx_mutex); cpuctx->ctx.type = cpu_context; cpuctx->ctx.pmu = pmu; cpuctx->jiffies_interval = 1; @@ -6127,7 +6136,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) * scheduled, so we are now safe from rescheduling changing * our context. */ - child_ctx = child->perf_event_ctxp[ctxn]; + child_ctx = rcu_dereference_raw(child->perf_event_ctxp[ctxn]); task_ctx_sched_out(child_ctx, EVENT_ALL); /* @@ -6440,11 +6449,6 @@ int perf_event_init_context(struct task_struct *child, int ctxn) unsigned long flags; int ret = 0; - child->perf_event_ctxp[ctxn] = NULL; - - mutex_init(&child->perf_event_mutex); - INIT_LIST_HEAD(&child->perf_event_list); - if (likely(!parent->perf_event_ctxp[ctxn])) return 0; @@ -6533,6 +6537,10 @@ int perf_event_init_task(struct task_struct *child) { int ctxn, ret; + memset(child->perf_event_ctxp, 0, sizeof(child->perf_event_ctxp)); + mutex_init(&child->perf_event_mutex); + INIT_LIST_HEAD(&child->perf_event_list); + for_each_task_context_nr(ctxn) { ret = perf_event_init_context(child, ctxn); if (ret) |