linux-kernel - INFO: suspicious RCU usage in rcu_torture

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Message-ID: <20120825033623.GA19330@localhost>
Date:	Sat, 25 Aug 2012 11:36:23 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Josh Triplett <josh@...htriplett.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: INFO: suspicious RCU usage in rcu_torture_writer()

Greetings,

I got this warning on 3.6.0-rc2. Full dmesg/config attached.

[    3.051375] Initializing RT-Tester: OK
[    3.052491] rcu-torture:--- Start of test: nreaders=2 nfakewriters=4 stat_interval=0 verbose=0 test_no_idle_hz=0 shuffle_interval=3 stut
ter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/1 test_boost_interval=7 test_boost_duration=4 shutdown_secs=0 onoff_interval=0 onoff_holdoff=0
[    3.059084] 
[    3.059451] ===============================
[    3.060454] [ INFO: suspicious RCU usage. ]
[    3.061482] 3.6.0-rc2-00010-g4c58c42 #59 Not tainted
[    3.062686] -------------------------------
[    3.063744] /c/kernel-tests/src/stable/kernel/rcutorture.c:990 suspicious rcu_dereference_check() usage!

 982         do {
 983                 schedule_timeout_uninterruptible(1);
 984                 rp = rcu_torture_alloc();
 985                 if (rp == NULL)
 986                         continue;
 987                 rp->rtort_pipe_count = 0;
 988                 udelay(rcu_random(&rand) & 0x3ff);
 989                 old_rp = rcu_dereference_check(rcu_torture_current,
>990                                                current == writer_task);
 991                 rp->rtort_mbtest = 1;
 992                 rcu_assign_pointer(rcu_torture_current, rp);
 993                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
 994                 if (old_rp) {

Thanks,
Fengguang

View attachment "dmesg-kvm-waimea-21045-2012-08-25-10-05-59-3.6.0-rc2-00010-g4c58c42-59" of type "text/plain" (48743 bytes)

View attachment "config-3.6.0-rc2-00010-g4c58c42" of type "text/plain" (65016 bytes)