From 70a0165752944e0be0b1de4a9020473079962c18 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 8 Jan 2016 09:29:16 +0100 Subject: [PATCH] perf: Fix cgroup scheduling in perf_enable_on_exec() There is a comment that states that perf_event_context_sched_in() will also switch in the cgroup events, I cannot find it does so. Therefore all the resulting logic goes out the window too. Clean that up. 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 --- kernel/events/core.c | 31 +++++++------------------------ 1 file changed, 7 insertions(+), 24 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 9d1195af819c..e7bda0ed8d40 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -579,13 +579,7 @@ static inline void perf_cgroup_sched_out(struct task_struct *task, * we are holding the rcu lock */ cgrp1 = perf_cgroup_from_task(task, NULL); - - /* - * next is NULL when called from perf_event_enable_on_exec() - * that will systematically cause a cgroup_switch() - */ - if (next) - cgrp2 = perf_cgroup_from_task(next, NULL); + cgrp2 = perf_cgroup_from_task(next, NULL); /* * only schedule out current cgroup events if we know @@ -611,8 +605,6 @@ static inline void perf_cgroup_sched_in(struct task_struct *prev, * we are holding the rcu lock */ cgrp1 = perf_cgroup_from_task(task, NULL); - - /* prev can never be NULL */ cgrp2 = perf_cgroup_from_task(prev, NULL); /* @@ -1450,11 +1442,14 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) if (is_cgroup_event(event)) { ctx->nr_cgroups--; + /* + * Because cgroup events are always per-cpu events, this will + * always be called from the right CPU. + */ cpuctx = __get_cpu_context(ctx); /* - * if there are no more cgroup events - * then cler cgrp to avoid stale pointer - * in update_cgrp_time_from_cpuctx() + * If there are no more cgroup events then clear cgrp to avoid + * stale pointer in update_cgrp_time_from_cpuctx(). */ if (!ctx->nr_cgroups) cpuctx->cgrp = NULL; @@ -3118,15 +3113,6 @@ static void perf_event_enable_on_exec(int ctxn) if (!ctx || !ctx->nr_events) goto out; - /* - * We must ctxsw out cgroup events to avoid conflict - * when invoking perf_task_event_sched_in() later on - * in this function. Otherwise we end up trying to - * ctxswin cgroup events which are already scheduled - * in. - */ - perf_cgroup_sched_out(current, NULL); - raw_spin_lock(&ctx->lock); task_ctx_sched_out(ctx); @@ -3144,9 +3130,6 @@ static void perf_event_enable_on_exec(int ctxn) raw_spin_unlock(&ctx->lock); - /* - * Also calls ctxswin for cgroup events, if any: - */ perf_event_context_sched_in(ctx, ctx->task); out: local_irq_restore(flags); -- 2.30.2