On Sat, 28 Jan, at 08:21:05AM, Mike Galbraith wrote: > Running Steven's hotplug stress script in tip.today. Config is > NOPREEMPT, tune for maximum build time (enterprise default-ish). > > [ 75.268049] x86: Booting SMP configuration: > [ 75.268052] smpboot: Booting Node 0 Processor 1 APIC 0x2 > [ 75.279994] smpboot: Booting Node 0 Processor 2 APIC 0x4 > [ 75.294617] smpboot: Booting Node 0 Processor 4 APIC 0x1 > [ 75.310698] smpboot: Booting Node 0 Processor 5 APIC 0x3 > [ 75.359056] smpboot: CPU 3 is now offline > [ 75.415505] smpboot: CPU 4 is now offline > [ 75.479985] smpboot: CPU 5 is now offline > [ 75.550674] ------------[ cut here ]------------ > [ 75.550678] WARNING: CPU: 1 PID: 15 at kernel/sched/sched.h:804 > assert_clock_updated.isra.62.part.63+0x25/0x27 > [ 75.550679] rq->clock_update_flags < RQCF_ACT_SKIP
The following patch queued in tip/sched/core should fix this issue: ---->8---- >From 4d25b35ea3729affd37d69c78191ce6f92766e1a Mon Sep 17 00:00:00 2001 From: Matt Fleming <[email protected]> Date: Wed, 26 Oct 2016 16:15:44 +0100 Subject: [PATCH] sched/fair: Restore previous rq_flags when migrating tasks in hotplug __migrate_task() can return with a different runqueue locked than the one we passed as an argument. So that we can repin the lock in migrate_tasks() (and keep the update_rq_clock() bit) we need to restore the old rq_flags before repinning. Note that it wouldn't be correct to change move_queued_task() to repin because of the change of runqueue and the fact that having an up-to-date clock on the initial rq doesn't mean the new rq has one too. Signed-off-by: Matt Fleming <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> --- kernel/sched/core.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7f983e83a353..3b248b03ad8f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5608,7 +5608,7 @@ static void migrate_tasks(struct rq *dead_rq) { struct rq *rq = dead_rq; struct task_struct *next, *stop = rq->stop; - struct rq_flags rf; + struct rq_flags rf, old_rf; int dest_cpu; /* @@ -5669,6 +5669,13 @@ 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); @@ -5677,6 +5684,7 @@ 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); } -- 2.10.0
