Re: rcu: frequent rcu lockups

[Paul E. McKenney]

On Wed, Mar 11, 2015 at 07:06:40PM -0400, Sasha Levin wrote:
> On 03/11/2015 07:01 PM, Paul E. McKenney wrote:
> >> With the commit I didn't hit it yet, but I do see 4 different WARNings:
> > I wish that I could say that I am surprised, but the sad fact is that
> > I am still shaking the bugs out.  
> 
> I have one more to add:
> 
> [   93.330539] WARNING: CPU: 1 PID: 8 at kernel/rcu/tree_plugin.h:476 rcu_gp_kthread+0x1eaa/0x4dd0()

A bit different, but still in the class of a combining-tree bitmask
handling bug.

							Thanx, Paul

> [   93.333515] Modules linked in:
> [   93.334678] CPU: 1 PID: 8 Comm: rcu_preempt Tainted: G        W       4.0.0-rc3-next-20150311-sasha-00035-g0a45b48-dirty #2052
> [   93.338402]  ffff8800496f8000 00000000f3e72ee7 ffff880049ac7b28 ffffffff9ea97e89
> [   93.339495]  0000000000000000 0000000000000000 ffff880049ac7b78 ffffffff941e242a
> [   93.339495]  ffffffffa1721038 ffffffff9433bf2a ffffffffa1721040 ffff8800a2822000
> [   93.339495] Call Trace:
> [   93.339495]  [<ffffffff9ea97e89>] dump_stack+0x4f/0x7b
> [   93.339495]  [<ffffffff941e242a>] warn_slowpath_common+0xca/0x130
> [   93.339495]  [<ffffffff9433bf2a>] ? rcu_gp_kthread+0x1eaa/0x4dd0
> [   93.339495]  [<ffffffff941e266a>] warn_slowpath_null+0x1a/0x20
> [   93.339495]  [<ffffffff9433bf2a>] rcu_gp_kthread+0x1eaa/0x4dd0
> [   93.339495]  [<ffffffff95f2346c>] ? plist_check_head+0x3c/0x50
> [   93.339495]  [<ffffffff9433a080>] ? cond_synchronize_rcu+0x20/0x20
> [   93.339495]  [<ffffffff942dffb5>] ? trace_hardirqs_on_caller+0x475/0x610
> [   93.339495]  [<ffffffff9eb0bdf9>] ? _raw_spin_unlock_irq+0x69/0xa0
> [   93.339495]  [<ffffffff9eaf95e3>] ? __schedule+0x993/0x1b90
> [   93.339495]  [<ffffffff95f49e39>] ? ___preempt_schedule+0x12/0x14
> [   93.339495]  [<ffffffff942c4530>] ? abort_exclusive_wait+0x1d0/0x1d0
> [   93.339495]  [<ffffffff9433a080>] ? cond_synchronize_rcu+0x20/0x20
> [   93.339495]  [<ffffffff94248b56>] kthread+0x216/0x2e0
> [   93.339495]  [<ffffffff94248940>] ? flush_kthread_work+0x300/0x300
> [   93.339495]  [<ffffffff9eb0bdc0>] ? _raw_spin_unlock_irq+0x30/0xa0
> [   93.339495]  [<ffffffff94248940>] ? flush_kthread_work+0x300/0x300
> [   93.339495]  [<ffffffff9eb0d293>] ret_from_fork+0x53/0x80
> [   93.339495]  [<ffffffff94248940>] ? flush_kthread_work+0x300/0x300
> 
> 
> Thanks,
> Sasha
> 

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