From 8cb68b343a66cf19834472012590490d34d31703 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 2 Feb 2017 16:55:06 +0100 Subject: [PATCH] sched/core: Fix update_rq_clock() splat on hotplug (and suspend/resume) The hotplug code still triggers the warning about using a stale rq->clock value. Fix things up to actually run update_rq_clock() in a place where we record the 'UPDATED' flag, and then modify the annotation to retain this flag over the rq->lock fiddling that happens as a result of actually migrating all the tasks elsewhere. Reported-by: Linus Torvalds Tested-by: Mike Galbraith Tested-by: Sachin Sant Tested-by: Borislav Petkov Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Matt Fleming Cc: Michael Ellerman Cc: Peter Zijlstra Cc: Ross Zwisler Cc: Thomas Gleixner Fixes: 4d25b35ea372 ("sched/fair: Restore previous rq_flags when migrating tasks in hotplug") Link: http://lkml.kernel.org/r/20170202155506.GX6515@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 34e2291a9a6c..2d6e828a0471 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5557,7 +5557,7 @@ static void migrate_tasks(struct rq *dead_rq) { struct rq *rq = dead_rq; struct task_struct *next, *stop = rq->stop; - struct rq_flags rf, old_rf; + struct rq_flags rf; int dest_cpu; /* @@ -5576,7 +5576,9 @@ static void migrate_tasks(struct rq *dead_rq) * class method both need to have an up-to-date * value of rq->clock[_task] */ + rq_pin_lock(rq, &rf); update_rq_clock(rq); + rq_unpin_lock(rq, &rf); for (;;) { /* @@ -5589,7 +5591,7 @@ static void migrate_tasks(struct rq *dead_rq) /* * pick_next_task() assumes pinned rq->lock: */ - rq_pin_lock(rq, &rf); + rq_repin_lock(rq, &rf); next = pick_next_task(rq, &fake_task, &rf); BUG_ON(!next); next->sched_class->put_prev_task(rq, next); @@ -5618,13 +5620,6 @@ static void migrate_tasks(struct rq *dead_rq) continue; } - /* - * __migrate_task() may return with a different - * rq->lock held and a new cookie in 'rf', but we need - * to preserve rf::clock_update_flags for 'dead_rq'. - */ - old_rf = rf; - /* Find suitable destination for @next, with force if needed. */ dest_cpu = select_fallback_rq(dead_rq->cpu, next); @@ -5633,7 +5628,6 @@ static void migrate_tasks(struct rq *dead_rq) raw_spin_unlock(&rq->lock); rq = dead_rq; raw_spin_lock(&rq->lock); - rf = old_rf; } raw_spin_unlock(&next->pi_lock); }