Message-ID: <5cc8b55c.1c69fb81.c3759.1c27@mx.google.com>
Date:   Tue, 30 Apr 2019 13:51:40 -0700 (PDT)
From:   "kernelci.org bot" <bot@...nelci.org>
To:     Tejun Heo <tj@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra (Intel) <peterz@...radead.org>,
        tomeu.vizoso@...labora.com, guillaume.tucker@...labora.com,
        mgalka@...labora.com, Thomas Gleixner <tglx@...utronix.de>,
        broonie@...nel.org, matthew.hart@...aro.org, khilman@...libre.com,
        enric.balletbo@...labora.com, Ingo Molnar <mingo@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "kernelci.org bot" <bot@...nelci.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>
Subject: next/master boot bisection: next-20190430 on beagle-xm

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* This automated bisection report was sent to you on the basis  *
* that you may be involved with the breaking commit it has      *
* found.  No manual investigation has been done to verify it,   *
* and the root cause of the problem may be somewhere else.      *
* Hope this helps!                                              *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

next/master boot bisection: next-20190430 on beagle-xm

Summary:
  Start:      f43b05fd4c17 Add linux-next specific files for 20190430
  Details:    https://kernelci.org/boot/id/5cc84d7359b514b7ab55847b
  Plain log:  https://storage.kernelci.org//next/master/next-20190430/arm/multi_v7_defconfig+CONFIG_SMP=n/gcc-7/lab-baylibre/boot-omap3-beagle-xm.txt
  HTML log:   https://storage.kernelci.org//next/master/next-20190430/arm/multi_v7_defconfig+CONFIG_SMP=n/gcc-7/lab-baylibre/boot-omap3-beagle-xm.html
  Result:     6d25be5782e4 sched/core, workqueues: Distangle worker accounting from rq lock

Checks:
  revert:     PASS
  verify:     PASS

Parameters:
  Tree:       next
  URL:        git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
  Branch:     master
  Target:     beagle-xm
  CPU arch:   arm
  Lab:        lab-baylibre
  Compiler:   gcc-7
  Config:     multi_v7_defconfig+CONFIG_SMP=n
  Test suite: boot

Breaking commit found:

-------------------------------------------------------------------------------
commit 6d25be5782e482eb93e3de0c94d0a517879377d0
Author: Thomas Gleixner <tglx@...utronix.de>
Date:   Wed Mar 13 17:55:48 2019 +0100

    sched/core, workqueues: Distangle worker accounting from rq lock
    
    The worker accounting for CPU bound workers is plugged into the core
    scheduler code and the wakeup code. This is not a hard requirement and
    can be avoided by keeping track of the state in the workqueue code
    itself.
    
    Keep track of the sleeping state in the worker itself and call the
    notifier before entering the core scheduler. There might be false
    positives when the task is woken between that call and actually
    scheduling, but that's not really different from scheduling and being
    woken immediately after switching away. When nr_running is updated when
    the task is retunrning from schedule() then it is later compared when it
    is done from ttwu().
    
    [ bigeasy: preempt_disable() around wq_worker_sleeping() by Daniel Bristot de Oliveira ]
    
    Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
    Acked-by: Tejun Heo <tj@...nel.org>
    Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
    Cc: Lai Jiangshan <jiangshanlai@...il.com>
    Cc: Linus Torvalds <torvalds@...ux-foundation.org>
    Cc: Peter Zijlstra <peterz@...radead.org>
    Link: http://lkml.kernel.org/r/ad2b29b5715f970bffc1a7026cabd6ff0b24076a.1532952814.git.bristot@redhat.com
    Signed-off-by: Ingo Molnar <mingo@...nel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4778c48a7fda..6184a0856aab 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1685,10 +1685,6 @@ static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_fl
 {
 	activate_task(rq, p, en_flags);
 	p->on_rq = TASK_ON_RQ_QUEUED;
-
-	/* If a worker is waking up, notify the workqueue: */
-	if (p->flags & PF_WQ_WORKER)
-		wq_worker_waking_up(p, cpu_of(rq));
 }
 
 /*
@@ -2106,56 +2102,6 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	return success;
 }
 
-/**
- * try_to_wake_up_local - try to wake up a local task with rq lock held
- * @p: the thread to be awakened
- * @rf: request-queue flags for pinning
- *
- * Put @p on the run-queue if it's not already there. The caller must
- * ensure that this_rq() is locked, @p is bound to this_rq() and not
- * the current task.
- */
-static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf)
-{
-	struct rq *rq = task_rq(p);
-
-	if (WARN_ON_ONCE(rq != this_rq()) ||
-	    WARN_ON_ONCE(p == current))
-		return;
-
-	lockdep_assert_held(&rq->lock);
-
-	if (!raw_spin_trylock(&p->pi_lock)) {
-		/*
-		 * This is OK, because current is on_cpu, which avoids it being
-		 * picked for load-balance and preemption/IRQs are still
-		 * disabled avoiding further scheduler activity on it and we've
-		 * not yet picked a replacement task.
-		 */
-		rq_unlock(rq, rf);
-		raw_spin_lock(&p->pi_lock);
-		rq_relock(rq, rf);
-	}
-
-	if (!(p->state & TASK_NORMAL))
-		goto out;
-
-	trace_sched_waking(p);
-
-	if (!task_on_rq_queued(p)) {
-		if (p->in_iowait) {
-			delayacct_blkio_end(p);
-			atomic_dec(&rq->nr_iowait);
-		}
-		ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK);
-	}
-
-	ttwu_do_wakeup(rq, p, 0, rf);
-	ttwu_stat(p, smp_processor_id(), 0);
-out:
-	raw_spin_unlock(&p->pi_lock);
-}
-
 /**
  * wake_up_process - Wake up a specific process
  * @p: The process to be woken up.
@@ -3472,19 +3418,6 @@ static void __sched notrace __schedule(bool preempt)
 				atomic_inc(&rq->nr_iowait);
 				delayacct_blkio_start();
 			}
-
-			/*
-			 * If a worker went to sleep, notify and ask workqueue
-			 * whether it wants to wake up a task to maintain
-			 * concurrency.
-			 */
-			if (prev->flags & PF_WQ_WORKER) {
-				struct task_struct *to_wakeup;
-
-				to_wakeup = wq_worker_sleeping(prev);
-				if (to_wakeup)
-					try_to_wake_up_local(to_wakeup, &rf);
-			}
 		}
 		switch_count = &prev->nvcsw;
 	}
@@ -3544,6 +3477,20 @@ static inline void sched_submit_work(struct task_struct *tsk)
 {
 	if (!tsk->state || tsk_is_pi_blocked(tsk))
 		return;
+
+	/*
+	 * If a worker went to sleep, notify and ask workqueue whether
+	 * it wants to wake up a task to maintain concurrency.
+	 * As this function is called inside the schedule() context,
+	 * we disable preemption to avoid it calling schedule() again
+	 * in the possible wakeup of a kworker.
+	 */
+	if (tsk->flags & PF_WQ_WORKER) {
+		preempt_disable();
+		wq_worker_sleeping(tsk);
+		preempt_enable_no_resched();
+	}
+
 	/*
 	 * If we are going to sleep and we have plugged IO queued,
 	 * make sure to submit it to avoid deadlocks.
@@ -3552,6 +3499,12 @@ static inline void sched_submit_work(struct task_struct *tsk)
 		blk_schedule_flush_plug(tsk);
 }
 
+static void sched_update_worker(struct task_struct *tsk)
+{
+	if (tsk->flags & PF_WQ_WORKER)
+		wq_worker_running(tsk);
+}
+
 asmlinkage __visible void __sched schedule(void)
 {
 	struct task_struct *tsk = current;
@@ -3562,6 +3515,7 @@ asmlinkage __visible void __sched schedule(void)
 		__schedule(false);
 		sched_preempt_enable_no_resched();
 	} while (need_resched());
+	sched_update_worker(tsk);
 }
 EXPORT_SYMBOL(schedule);
 
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ddee541ea97a..56180c9286f5 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -841,43 +841,32 @@ static void wake_up_worker(struct worker_pool *pool)
 }
 
 /**
- * wq_worker_waking_up - a worker is waking up
+ * wq_worker_running - a worker is running again
  * @task: task waking up
- * @cpu: CPU @task is waking up to
  *
- * This function is called during try_to_wake_up() when a worker is
- * being awoken.
- *
- * CONTEXT:
- * spin_lock_irq(rq->lock)
+ * This function is called when a worker returns from schedule()
  */
-void wq_worker_waking_up(struct task_struct *task, int cpu)
+void wq_worker_running(struct task_struct *task)
 {
 	struct worker *worker = kthread_data(task);
 
-	if (!(worker->flags & WORKER_NOT_RUNNING)) {
-		WARN_ON_ONCE(worker->pool->cpu != cpu);
+	if (!worker->sleeping)
+		return;
+	if (!(worker->flags & WORKER_NOT_RUNNING))
 		atomic_inc(&worker->pool->nr_running);
-	}
+	worker->sleeping = 0;
 }
 
 /**
  * wq_worker_sleeping - a worker is going to sleep
  * @task: task going to sleep
  *
- * This function is called during schedule() when a busy worker is
- * going to sleep.  Worker on the same cpu can be woken up by
- * returning pointer to its task.
- *
- * CONTEXT:
- * spin_lock_irq(rq->lock)
- *
- * Return:
- * Worker task on @cpu to wake up, %NULL if none.
+ * This function is called from schedule() when a busy worker is
+ * going to sleep.
  */
-struct task_struct *wq_worker_sleeping(struct task_struct *task)
+void wq_worker_sleeping(struct task_struct *task)
 {
-	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
+	struct worker *next, *worker = kthread_data(task);
 	struct worker_pool *pool;
 
 	/*
@@ -886,13 +875,15 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task)
 	 * checking NOT_RUNNING.
 	 */
 	if (worker->flags & WORKER_NOT_RUNNING)
-		return NULL;
+		return;
 
 	pool = worker->pool;
 
-	/* this can only happen on the local cpu */
-	if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
-		return NULL;
+	if (WARN_ON_ONCE(worker->sleeping))
+		return;
+
+	worker->sleeping = 1;
+	spin_lock_irq(&pool->lock);
 
 	/*
 	 * The counterpart of the following dec_and_test, implied mb,
@@ -906,9 +897,12 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task)
 	 * lock is safe.
 	 */
 	if (atomic_dec_and_test(&pool->nr_running) &&
-	    !list_empty(&pool->worklist))
-		to_wakeup = first_idle_worker(pool);
-	return to_wakeup ? to_wakeup->task : NULL;
+	    !list_empty(&pool->worklist)) {
+		next = first_idle_worker(pool);
+		if (next)
+			wake_up_process(next->task);
+	}
+	spin_unlock_irq(&pool->lock);
 }
 
 /**
@@ -4929,7 +4923,7 @@ static void rebind_workers(struct worker_pool *pool)
 		 *
 		 * WRITE_ONCE() is necessary because @worker->flags may be
 		 * tested without holding any lock in
-		 * wq_worker_waking_up().  Without it, NOT_RUNNING test may
+		 * wq_worker_running().  Without it, NOT_RUNNING test may
 		 * fail incorrectly leading to premature concurrency
 		 * management operations.
 		 */
diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index cb68b03ca89a..498de0e909a4 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -44,6 +44,7 @@ struct worker {
 	unsigned long		last_active;	/* L: last active timestamp */
 	unsigned int		flags;		/* X: flags */
 	int			id;		/* I: worker id */
+	int			sleeping;	/* None */
 
 	/*
 	 * Opaque string set with work_set_desc().  Printed out with task
@@ -72,8 +73,8 @@ static inline struct worker *current_wq_worker(void)
  * Scheduler hooks for concurrency managed workqueue.  Only to be used from
  * sched/ and workqueue.c.
  */
-void wq_worker_waking_up(struct task_struct *task, int cpu);
-struct task_struct *wq_worker_sleeping(struct task_struct *task);
+void wq_worker_running(struct task_struct *task);
+void wq_worker_sleeping(struct task_struct *task);
 work_func_t wq_worker_last_func(struct task_struct *task);
 
 #endif /* _KERNEL_WORKQUEUE_INTERNAL_H */
-------------------------------------------------------------------------------


Git bisection log:

-------------------------------------------------------------------------------
git bisect start
# good: [80871482fd5cb1cb396ea232237a7d9c540854f9] x86: make ZERO_PAGE() at least parse its argument
git bisect good 80871482fd5cb1cb396ea232237a7d9c540854f9
# bad: [f43b05fd4c176d42c7b3f3b99643910486fc49c8] Add linux-next specific files for 20190430
git bisect bad f43b05fd4c176d42c7b3f3b99643910486fc49c8
# good: [5581b5dd6d5a20de0a40ac8975ca66fe15324293] Merge remote-tracking branch 'crypto/master'
git bisect good 5581b5dd6d5a20de0a40ac8975ca66fe15324293
# good: [3ed1aaa4720275e2c6f94e109805472d55969148] Merge remote-tracking branch 'spi/for-next'
git bisect good 3ed1aaa4720275e2c6f94e109805472d55969148
# bad: [0606c6c8fc2478eb7d09202444412d4f9b484076] Merge remote-tracking branch 'staging/staging-next'
git bisect bad 0606c6c8fc2478eb7d09202444412d4f9b484076
# bad: [f0ca99b2ef58eb1d0509b996c9f4b16cb37780d0] Merge remote-tracking branch 'usb-serial/usb-next'
git bisect bad f0ca99b2ef58eb1d0509b996c9f4b16cb37780d0
# bad: [ded23883f168101a4de43e87f9329ee7fcdd540f] Merge branch 'locking/core'
git bisect bad ded23883f168101a4de43e87f9329ee7fcdd540f
# bad: [0dc77d22166d637e69728dde0121764b35f6d18e] Merge branch 'perf/core'
git bisect bad 0dc77d22166d637e69728dde0121764b35f6d18e
# good: [7a525b0cc661abb2d9004f619406df0fbe480106] Merge branch 'x86/asm'
git bisect good 7a525b0cc661abb2d9004f619406df0fbe480106
# good: [477f00f9617009a9a3a9271885231573b728ca4f] perf/x86/intel/ds: Extract code of event update in short period
git bisect good 477f00f9617009a9a3a9271885231573b728ca4f
# bad: [146b2c0aea6a74c5c22b6f0bb68b17f7601c3fea] Merge branch 'sched/core'
git bisect bad 146b2c0aea6a74c5c22b6f0bb68b17f7601c3fea
# bad: [ad2e379def135ebc079f89a0e0b1d987d243f949] sched/debug: Fix spelling mistake "logaritmic" -> "logarithmic"
git bisect bad ad2e379def135ebc079f89a0e0b1d987d243f949
# bad: [6d25be5782e482eb93e3de0c94d0a517879377d0] sched/core, workqueues: Distangle worker accounting from rq lock
git bisect bad 6d25be5782e482eb93e3de0c94d0a517879377d0
# good: [7ba7319f9e3898101bff5d63cbae5a6cc174c8c9] sched/core: Annotate perf_domain pointer with __rcu
git bisect good 7ba7319f9e3898101bff5d63cbae5a6cc174c8c9
# good: [d8743230c9f4e92f370ecd2a90c680ddcede6ae5] sched/topology: Fix build_sched_groups() comment
git bisect good d8743230c9f4e92f370ecd2a90c680ddcede6ae5
# good: [e2abb398115e9c33f3d1e25bf6d1d08badc58b13] sched/fair: Remove unneeded prototype of capacity_of()
git bisect good e2abb398115e9c33f3d1e25bf6d1d08badc58b13
# first bad commit: [6d25be5782e482eb93e3de0c94d0a517879377d0] sched/core, workqueues: Distangle worker accounting from rq lock
-------------------------------------------------------------------------------

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