linux-kernel - [rcu] INFO: suspicious RCU usage.

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Date:	Thu, 5 Feb 2015 06:09:42 -0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: [rcu] INFO: suspicious RCU usage.

FYI, we noticed the below changes on

git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
commit 8161f989ebe957022f59bf899290a7818a818c9f ("rcu: Handle outgoing CPUs on exit from idle loop")


+-------------------------------------+------------+------------+
|                                     | 51821d3ce8 | 8161f989eb |
+-------------------------------------+------------+------------+
| boot_successes                      | 576        | 120        |
| boot_failures                       | 0          | 72         |
| INFO:suspicious_RCU_usage           | 0          | 72         |
| RCU_used_illegally_from_offline_CPU | 0          | 72         |
| backtrace:cpu_startup_entry         | 0          | 72         |
+-------------------------------------+------------+------------+


[   14.800098] numa_remove_cpu cpu 0 node 0: mask now 1
[   14.801490] 
[   14.801490] ===============================
[   14.801490] [ INFO: suspicious RCU usage. ]
[   14.801490] 3.19.0-rc6-gaac5362 #543 Not tainted
[   14.801490] -------------------------------
[   14.801490] include/trace/events/rcu.h:35 suspicious rcu_dereference_check() usage!
[   14.801490] 
[   14.801490] other info that might help us debug this:
[   14.801490] 
[   14.801490] 
[   14.801490] RCU used illegally from offline CPU!
[   14.801490] rcu_scheduler_active = 1, debug_locks = 0
[   14.801490] no locks held by swapper/0/0.
[   14.801490] 
[   14.801490] stack backtrace:
[   14.801490] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.19.0-rc6-gaac5362 #543
[   14.801490]  0000000000000001 ffffffff81e03e08 ffffffff81724e42 0000000000000000
[   14.801490]  ffffffff81e0e580 ffffffff81e03e38 ffffffff810efb1b ffffffff81e4b140
[   14.801490]  ffffffff81c7c455 0000000000000002 ffffffff81e11e98 ffffffff81e03e58
[   14.801490] Call Trace:
[   14.801490]  [<ffffffff81724e42>] dump_stack+0x7f/0xa7
[   14.801490]  [<ffffffff810efb1b>] lockdep_rcu_suspicious+0x107/0x110
[   14.801490]  [<ffffffff81110d9d>] trace_rcu_utilization+0x127/0x133
[   14.801490]  [<ffffffff81112358>] rcu_cpu_notify+0x527/0x53b
[   14.801490]  [<ffffffff810e93cc>] cpu_startup_entry+0x1dc/0x4ea
[   14.801490]  [<ffffffff817180a7>] rest_init+0x159/0x15f
[   14.801490]  [<ffffffff823822da>] start_kernel+0x565/0x572
[   14.801490]  [<ffffffff82381120>] ? early_idt_handlers+0x120/0x120
[   14.801490]  [<ffffffff823814e4>] x86_64_start_reservations+0x41/0x43
[   14.801490]  [<ffffffff82381623>] x86_64_start_kernel+0x13d/0x14c
[   14.817365] CPU 0 is now offline
[   14.818299] debug: unmapping init [mem 0xffffffff8236c000-0xffffffff82540fff]
[   14.819139] Write protecting the kernel read-only data: 14336k

Thanks,
Fengguang

View attachment "config-3.19.0-rc1-g8161f98" of type "text/plain" (76153 bytes)

View attachment ".dmesg" of type "text/plain" (29900 bytes)

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