linux-kernel - Re: [PATCH tip/core/rcu 0/2] more lockdep-RCU and RCU_FAST_NO

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Date:	Sun, 28 Feb 2010 09:55:05 +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] more lockdep-RCU and RCU_FAST_NO_HZ
 fixes


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

> Hello!
> 
> This series (1) makes RCU_FAST_NO_HZ actually do the full number of
> iterations specified instead of just one and (2) fixes an RCU lockdep
> splat.

Thanks, applied.

This one is pretty stubborn, it still triggers:

[    0.000000]       soft-irq read-recursion/321:  ok  |
[    0.000000] -------------------------------------------------------
[    0.000000] Good, all 218 testcases passed! |
[    0.000000] ---------------------------------
[    0.000000] allocated 10485760 bytes of page_cgroup
[    0.000000] please try 'cgroup_disable=memory' option if you don't want memory cgroups
[    0.000000] 
[    0.000000] ===================================================
[    0.000000] [ INFO: suspicious rcu_dereference_check() usage. ]
[    0.000000] ---------------------------------------------------
[    0.000000] kernel/sched_fair.c:3479 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-01015-g97e7da3-dirty #10753
[    0.000000] Call Trace:
[    0.000000]  <IRQ>  [<ffffffff8107f5d1>] lockdep_rcu_dereference+0xa1/0xb0
[    0.000000]  [<ffffffff8104afd1>] scheduler_tick+0x221/0x2c0
[    0.000000]  [<ffffffff8105f6d5>] update_process_times+0x55/0x70
[    0.000000]  [<ffffffff8107ac27>] tick_periodic+0x27/0x70
[    0.000000]  [<ffffffff8107ac8f>] tick_handle_periodic+0x1f/0x90
[    0.000000]  [<ffffffff8100e29a>] timer_interrupt+0x1a/0x30
[    0.000000]  [<ffffffff810a28aa>] handle_IRQ_event+0x3a/0xe0
[    0.000000]  [<ffffffff810a53ab>] handle_level_irq+0x8b/0x130
[    0.000000]  [<ffffffff8100da94>] handle_irq+0x44/0x70
[    0.000000]  [<ffffffff8100cfde>] do_IRQ+0x6e/0xf0
[    0.000000]  [<ffffffff817eea13>] ret_from_intr+0x0/0x16
[    0.000000]  <EOI>  [<ffffffff8102dfe6>] ? native_restore_fl+0x6/0x10
[    0.000000]  [<ffffffff817ee3df>] _raw_spin_unlock_irqrestore+0x6f/0x80
[    0.000000]  [<ffffffff810a37f3>] __setup_irq+0x1b3/0x3b0
[    0.000000]  [<ffffffff810a3a18>] setup_irq+0x28/0x40
[    0.000000]  [<ffffffff81ef2914>] setup_default_timer_irq+0x12/0x14
[    0.000000]  [<ffffffff81ef292d>] hpet_time_init+0x17/0x19
[    0.000000]  [<ffffffff81ef28fb>] x86_late_time_init+0xa/0x11
[    0.000000]  [<ffffffff81eefcf4>] start_kernel+0x25f/0x2e6
[    0.000000]  [<ffffffff81eef30b>] x86_64_start_reservations+0xf6/0xfa
[    0.000000]  [<ffffffff81eef409>] x86_64_start_kernel+0xfa/0x109
[    0.000000] Fast TSC calibration using PIT
[    0.000000] Detected 2002.507 MHz processor.
[    0.004004] Calibrating delay loop (skipped), value calculated using timer frequency.. 4005.01 BogoMIPS (lpj=2002507)

	Ingo

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