3.14.61-rt63-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra Upstream commit fbd705a0c6184580d0e2fbcbd47a37b6e5822511 Mathieu reported that since 317f394160e9 ("sched: Move the second half of ttwu() to the remote cpu") trace_sched_wakeup() can happen out of context of the waker. This is a problem when you want to analyse wakeup paths because it is now very hard to correlate the wakeup event to whoever issued the wakeup. OTOH trace_sched_wakeup() is issued at the point where we set p->state = TASK_RUNNING, which is right were we hand the task off to the scheduler, so this is an important point when looking at scheduling behaviour, up to here its been the wakeup path everything hereafter is due to scheduler policy. To bridge this gap, introduce a second tracepoint: trace_sched_waking. It is guaranteed to be called in the waker context. [ Ported to linux-4.1.y-rt kernel by Mathieu Desnoyers. Resolved conflict: try_to_wake_up_local() does not exist in -rt kernel. Removed its instrumentation hunk. ] Reported-by: Mathieu Desnoyers CC: Julien Desfossez CC: Peter Zijlstra (Intel) Cc: Francis Giraldeau Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner CC: Ingo Molnar Link: http://lkml.kernel.org/r/20150609091336.GQ3644@twins.programming.kicks-ass.net Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt --- include/trace/events/sched.h | 30 +++++++++++++++++++++--------- kernel/sched/core.c | 8 +++++--- kernel/trace/trace_sched_switch.c | 2 +- kernel/trace/trace_sched_wakeup.c | 2 +- 4 files changed, 28 insertions(+), 14 deletions(-) diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h index dc7bb01f580f..67b26cdf3f52 100644 --- a/include/trace/events/sched.h +++ b/include/trace/events/sched.h @@ -55,9 +55,9 @@ TRACE_EVENT(sched_kthread_stop_ret, */ DECLARE_EVENT_CLASS(sched_wakeup_template, - TP_PROTO(struct task_struct *p, int success), + TP_PROTO(struct task_struct *p), - TP_ARGS(__perf_task(p), success), + TP_ARGS(__perf_task(p)), TP_STRUCT__entry( __array( char, comm, TASK_COMM_LEN ) @@ -71,25 +71,37 @@ DECLARE_EVENT_CLASS(sched_wakeup_template, memcpy(__entry->comm, p->comm, TASK_COMM_LEN); __entry->pid = p->pid; __entry->prio = p->prio; - __entry->success = success; + __entry->success = 1; /* rudiment, kill when possible */ __entry->target_cpu = task_cpu(p); ), - TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d", + TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d", __entry->comm, __entry->pid, __entry->prio, - __entry->success, __entry->target_cpu) + __entry->target_cpu) ); +/* + * Tracepoint called when waking a task; this tracepoint is guaranteed to be + * called from the waking context. + */ +DEFINE_EVENT(sched_wakeup_template, sched_waking, + TP_PROTO(struct task_struct *p), + TP_ARGS(p)); + +/* + * Tracepoint called when the task is actually woken; p->state == TASK_RUNNNG. + * It it not always called from the waking context. + */ DEFINE_EVENT(sched_wakeup_template, sched_wakeup, - TP_PROTO(struct task_struct *p, int success), - TP_ARGS(p, success)); + TP_PROTO(struct task_struct *p), + TP_ARGS(p)); /* * Tracepoint for waking up a new task: */ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new, - TP_PROTO(struct task_struct *p, int success), - TP_ARGS(p, success)); + TP_PROTO(struct task_struct *p), + TP_ARGS(p)); #ifdef CREATE_TRACE_POINTS static inline long __trace_sched_switch_state(struct task_struct *p) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a570a5846af2..edacb6d1d2bf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1481,9 +1481,9 @@ static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) { check_preempt_curr(rq, p, wake_flags); - trace_sched_wakeup(p, true); - p->state = TASK_RUNNING; + trace_sched_wakeup(p); + #ifdef CONFIG_SMP if (p->sched_class->task_woken) p->sched_class->task_woken(rq, p); @@ -1676,6 +1676,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) if (!(wake_flags & WF_LOCK_SLEEPER)) p->saved_state = TASK_RUNNING; + trace_sched_waking(p); + success = 1; /* we're going to change ->state */ cpu = task_cpu(p); @@ -2078,7 +2080,7 @@ void wake_up_new_task(struct task_struct *p) rq = __task_rq_lock(p); activate_task(rq, p, 0); p->on_rq = 1; - trace_sched_wakeup_new(p, true); + trace_sched_wakeup_new(p); check_preempt_curr(rq, p, WF_FORK); #ifdef CONFIG_SMP if (p->sched_class->task_woken) diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c index 3f34dc9b40f3..9586cde520b0 100644 --- a/kernel/trace/trace_sched_switch.c +++ b/kernel/trace/trace_sched_switch.c @@ -106,7 +106,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr, } static void -probe_sched_wakeup(void *ignore, struct task_struct *wakee, int success) +probe_sched_wakeup(void *ignore, struct task_struct *wakee) { struct trace_array_cpu *data; unsigned long flags; diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c index 6e32635e5e57..32eea7ba8c4a 100644 --- a/kernel/trace/trace_sched_wakeup.c +++ b/kernel/trace/trace_sched_wakeup.c @@ -462,7 +462,7 @@ static void wakeup_reset(struct trace_array *tr) } static void -probe_wakeup(void *ignore, struct task_struct *p, int success) +probe_wakeup(void *ignore, struct task_struct *p) { struct trace_array_cpu *data; int cpu = smp_processor_id(); -- 2.7.0