linux-kernel - Re: [PATCH tip/core/rcu 0/2] rcu: fixes for RCU lockdep

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Message-ID: <20100226115018.GA4519@elte.hu>
Date:	Fri, 26 Feb 2010 12:50:18 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	dvhltc@...ibm.com, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com
Subject: Re: [PATCH tip/core/rcu 0/2] rcu: fixes for RCU lockdep


* Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:

> Hello!
> 
> This set fixes a couple of problems with the RCU-based lockdep patches:
> 
> 1.	Make the lockdep_rcu_dereference() message less alarmist
> 
> 2.	Make rcu_read_lock_sched_held() take boot-time lack of
> 	preemption into account.
> 
> 							Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
>  include/linux/rcupdate.h |    4 +++-
>  include/linux/rcutiny.h  |    4 ----
>  include/linux/rcutree.h  |    1 -
>  kernel/lockdep.c         |    7 +++----
>  kernel/rcupdate.c        |   18 ++++++++++++++++++
>  kernel/rcutree.c         |   20 --------------------
>  6 files changed, 24 insertions(+), 30 deletions(-)

Applied, thanks Paul!

Here's a new warning:

[    0.000000] 
[    0.000000] ===================================================
[    0.000000] [ INFO: suspicious rcu_dereference_check() usage. ]
[    0.000000] ---------------------------------------------------
[    0.000000] kernel/sched_fair.c:3469 invoked rcu_dereference_check() without protection!
[    0.000000] 
[    0.000000] other info that might help us debug this:
[    0.000000] 
[    0.000000] no locks held by swapper/0.
[    0.000000] 
[    0.000000] stack backtrace:
[    0.000000] Pid: 0, comm: swapper Not tainted 2.6.33-tip+ #18801
[    0.000000] Call Trace:
[    0.000000]  [<c1f01af4>] ? printk+0x1d/0x1f
[    0.000000]  [<c10a08ac>] lockdep_rcu_dereference+0x8c/0x90
[    0.000000]  [<c1061c31>] scheduler_tick+0x211/0x290
[    0.000000]  [<c107b8ac>] update_process_times+0x4c/0x70
[    0.000000]  [<c109b4aa>] tick_periodic+0x2a/0x80
[    0.000000]  [<c109b51d>] tick_handle_periodic+0x1d/0x90
[    0.000000]  [<c102de16>] timer_interrupt+0x26/0x70
[    0.000000]  [<c10baeb4>] handle_IRQ_event+0x44/0x1c0
[    0.000000]  [<c10a440a>] ? lock_release+0x9a/0x200
[    0.000000]  [<c10bd777>] handle_level_irq+0x77/0xf0
[    0.000000]  [<c10bd700>] ? handle_level_irq+0x0/0xf0
[    0.000000]  <IRQ>  [<c1f0630f>] ? do_IRQ+0x4f/0xc0
[    0.000000]  [<c109eeae>] ? trace_hardirqs_off_caller+0x7e/0xb0
[    0.000000]  [<c102b20e>] ? common_interrupt+0x2e/0x34
[    0.000000]  [<c104c10a>] ? native_restore_fl+0xa/0x10
[    0.000000]  [<c1f05365>] ? _raw_spin_unlock_irqrestore+0x65/0x80
[    0.000000]  [<c10bbde6>] ? __setup_irq+0x176/0x310
[    0.000000]  [<c105c9c9>] ? sub_preempt_count+0x9/0xc0
[    0.000000]  [<c1f05344>] ? _raw_spin_unlock_irqrestore+0x44/0x80
[    0.000000]  [<c10bbfa6>] ? setup_irq+0x26/0x40
[    0.000000]  [<c25d9abe>] ? setup_default_timer_irq+0xf/0x11
[    0.000000]  [<c25d9ad6>] ? hpet_time_init+0x16/0x18
[    0.000000]  [<c25d9aa8>] ? x86_late_time_init+0x9/0x10
[    0.000000]  [<c25d691e>] ? start_kernel+0x34f/0x3c4
[    0.000000]  [<c25d63f9>] ? unknown_bootoption+0x0/0x1a0
[    0.000000]  [<c25d6140>] ? reserve_ebda_region+0x70/0x72
[    0.000000]  [<c25d60c9>] ? i386_start_kernel+0xc9/0xd0
[    0.000000] Fast TSC calibration using PIT
[    0.000000] Detected 2010.433 MHz processor.
[    0.030007] Calibrating delay loop (skipped), value calculated using timer frequency.. 4020.86 BogoMIPS (lpj=20104330)
[    0.042949] Security Framework initialized

Config attached.

	Ingo

View attachment "config" of type "text/plain" (74257 bytes)