Messages in this thread Patch in this message | | | Subject | Re: task blocked for more than 120 seconds | From | Peter Zijlstra <> | Date | Thu, 04 Nov 2010 18:32:26 +0100 |
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On Thu, 2010-11-04 at 17:19 +0100, Markus Trippelsdorf wrote: > On Thu, Nov 04, 2010 at 05:58:26PM +0200, Sergey Senozhatsky wrote: > > Hello, > > Got the following traces: > > > > [42001.449295] INFO: task openbox:17761 blocked for more than 120 seconds. > > [42001.449303] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > [42001.449311] openbox D 0000000000000003 0 17761 3723 0x00000000 > > [42001.449321] ffff88004ce8dc38 0000000000000046 0000000000000000 ffff88004ce8c000 > > [42001.449333] ffff88004ce8dfd8 0000000000012040 ffff880133010000 ffff88004ce8dfd8 > > [42001.449343] 0000000000012040 0000000000012040 ffff88004ce8dfd8 0000000000012040 > > [42001.449354] Call Trace: > > [42001.449369] [<ffffffff814212ff>] schedule_timeout+0x38/0x220 > > [42001.449381] [<ffffffff81066f21>] ? mark_held_locks+0x50/0x72 > > [42001.449389] [<ffffffff81423dae>] ? _raw_spin_unlock_irq+0x2b/0x59 > > [42001.449398] [<ffffffff81036070>] ? get_parent_ip+0x11/0x41 > > [42001.449406] [<ffffffff81036132>] ? sub_preempt_count+0x92/0xa5 > > [42001.449413] [<ffffffff8142057e>] wait_for_common+0xca/0x144 > > [42001.449421] [<ffffffff81038b13>] ? default_wake_function+0x0/0xf > > [42001.449429] [<ffffffff81423e4b>] ? _raw_spin_unlock_irqrestore+0x6f/0x74 > > [42001.449436] [<ffffffff81420692>] wait_for_completion+0x18/0x1a > > [42001.449445] [<ffffffff81084808>] stop_one_cpu+0x8c/0xba > > These traces look related to: > http://article.gmane.org/gmane.linux.kernel/1055100 > > Does reverting 34f971f6f7988be4d014eec3e3526bee6d007ffa help in your > case?
--- Subject: sched: Fixup cross sched_class wakeup preemption From: Peter Zijlstra <a.p.zijlstra@chello.nl> Date: Sun Oct 31 12:37:04 CET 2010
Instead of dealing with sched classes inside each check_preempt_curr() implementation, pull out this logic into the generic wakeup preemption path.
This fixes a hang in KVM (and others) where we are waiting for the stop machine thread to run..
Tested-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> --- kernel/sched.c | 39 ++++++++++++++++++++++++++++----------- kernel/sched_fair.c | 6 ------ kernel/sched_stoptask.c | 2 +- 3 files changed, 29 insertions(+), 18 deletions(-)
Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -560,18 +560,9 @@ struct rq { static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); -static inline -void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) -{ - rq->curr->sched_class->check_preempt_curr(rq, p, flags); - /* - * A queue event has occurred, and we're going to schedule. In - * this case, we can save a useless back to back clock update. - */ - if (test_tsk_need_resched(p)) - rq->skip_clock_update = 1; -} +static inline +void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags); static inline int cpu_of(struct rq *rq) { @@ -9400,4 +9391,30 @@ void synchronize_sched_expedited(void) } EXPORT_SYMBOL_GPL(synchronize_sched_expedited); +static inline +void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) +{ + const struct sched_class *class; + + if (p->sched_class == rq->curr->sched_class) + rq->curr->sched_class->check_preempt_curr(rq, p, flags); + + for_each_class(class) { + if (class == rq->curr->sched_class) + break; + if (class == p->sched_class) { + resched_task(rq->curr); + break; + } + } + + /* + * A queue event has occurred, and we're going to schedule. In + * this case, we can save a useless back to back clock update. + */ + if (test_tsk_need_resched(rq->curr)) + rq->skip_clock_update = 1; +} + + #endif /* #else #ifndef CONFIG_SMP */ Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -1654,12 +1654,6 @@ static void check_preempt_wakeup(struct struct cfs_rq *cfs_rq = task_cfs_rq(curr); int scale = cfs_rq->nr_running >= sched_nr_latency; - if (unlikely(rt_prio(p->prio))) - goto preempt; - - if (unlikely(p->sched_class != &fair_sched_class)) - return; - if (unlikely(se == pse)) return; Index: linux-2.6/kernel/sched_stoptask.c =================================================================== --- linux-2.6.orig/kernel/sched_stoptask.c +++ linux-2.6/kernel/sched_stoptask.c @@ -19,7 +19,7 @@ select_task_rq_stop(struct rq *rq, struc static void check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags) { - resched_task(rq->curr); /* we preempt everything */ + /* we're never preempted */ } static struct task_struct *pick_next_task_stop(struct rq *rq)
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