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

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Message-ID: <20100301121045.GA30901@elte.hu>
Date:	Mon, 1 Mar 2010 13:10:45 +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


FYI, even with your patch applied i'm getting this in -tip testing:

[    0.000000] Memory: 914996k/1047744k available (15146k kernel code, 452k absent, 131584k reserved, 12516k data, 2552k init)
[    0.000000] SLUB: Genslabs=13, HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[    0.000000] 
[    0.000000] ===================================================
[    0.000000] [ INFO: suspicious rcu_dereference_check() usage. ]
[    0.000000] ---------------------------------------------------
[    0.000000] include/linux/cgroup.h:492 invoked rcu_dereference_check() without protection!
[    0.000000] 
[    0.000000] other info that might help us debug this:
[    0.000000] 
[    0.000000] 1 lock held by swapper/0:
[    0.000000]  #0:  (&rq->lock){......}, at: [<ffffffff81ec0bad>] init_idle+0x31/0x1ee
[    0.000000] 
[    0.000000] stack backtrace:
[    0.000000] Pid: 0, comm: swapper Not tainted 2.6.33-tip+ #10563
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff810ad1c1>] lockdep_rcu_dereference+0xa1/0xb0
[    0.000000]  [<ffffffff81ec0cbd>] init_idle+0x141/0x1ee
[    0.000000]  [<ffffffff82ceff40>] sched_init+0x43a/0x4b6
[    0.000000]  [<ffffffff82cdcceb>] start_kernel+0x1b3/0x49e
[    0.000000]  [<ffffffff82cdc319>] x86_64_start_reservations+0x120/0x124
[    0.000000]  [<ffffffff82cdc46b>] x86_64_start_kernel+0x14e/0x15d
[    0.000000] Hierarchical RCU implementation.
[    0.000000] RCU-based detection of stalled CPUs is enabled.
[    0.000000] NR_IRQS:4352

Config attached.

The sha1 is:

  b5fabe1: Merge branch 'perf/urgent'

i.e. your latest fix is included:

  90a6501: sched, rcu: Fix rcu_dereference() for RCU-lockdep

Thanks,

	Ingo

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