LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Petr Mladek <pmladek@suse.com>,
	Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tony Lindgren <tony@atomide.com>,
	Russell King <rmk@armlinux.org.uk>,
	linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	"[3.4+]" <stable@vger.kernel.org>
Subject: [PATCH] printk: use rcuidle console tracepoint
Date: Fri, 17 Feb 2017 10:59:32 +0900
Message-ID: <20170217015932.11898-1-sergey.senozhatsky@gmail.com> (raw)

Use rcuidle console tracepoint because, apparently, it may be issued
from an idle CPU:

[    2.581939] hw-breakpoint: Failed to enable monitor mode on CPU 0.
[    2.591613] hw-breakpoint: CPU 0 failed to disable vector catch
[    2.597686]
[    2.597717] ===============================
[    2.597717] [ ERR: suspicious RCU usage.  ]
[    2.597717] 4.10.0-rc8-next-20170215+ #119 Not tainted
[    2.597717] -------------------------------
[    2.597717] ./include/trace/events/printk.h:32 suspicious rcu_dereference_check() usage!
[    2.597717]
[    2.597717] other info that might help us debug this:
[    2.597717]
[    2.597717]
[    2.597717] RCU used illegally from idle CPU!
[    2.597717] rcu_scheduler_active = 2, debug_locks = 0
[    2.597747] RCU used illegally from extended quiescent state!
[    2.597747] 2 locks held by swapper/0/0:
[    2.597747]  #0:  (cpu_pm_notifier_lock){......}, at: [<c0237e2c>] cpu_pm_exit+0x10/0x54
[    2.597747]  #1:  (console_lock){+.+.+.}, at: [<c01ab350>] vprintk_emit+0x264/0x474
[    2.597747]
[    2.597747] stack backtrace:
[    2.597778] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.10.0-rc8-next-20170215+ #119
[    2.597778] Hardware name: Generic OMAP4 (Flattened Device Tree)
[    2.597778] [<c0110228>] (unwind_backtrace) from [<c010c224>] (show_stack+0x10/0x14)
[    2.597778] [<c010c224>] (show_stack) from [<c04ca8a0>] (dump_stack+0xac/0xe0)
[    2.597778] [<c04ca8a0>] (dump_stack) from [<c01ab084>] (console_unlock+0x5e8/0x650)
[    2.597778] [<c01ab084>] (console_unlock) from [<c01ab35c>] (vprintk_emit+0x270/0x474)
[    2.597778] [<c01ab35c>] (vprintk_emit) from [<c01ab6f0>] (vprintk_default+0x20/0x28)
[    2.597808] [<c01ab6f0>] (vprintk_default) from [<c0250c94>] (printk+0x20/0x30)
[    2.597808] [<c0250c94>] (printk) from [<c0111004>] (reset_ctrl_regs+0x108/0x288)
[    2.597808] [<c0111004>] (reset_ctrl_regs) from [<c0111220>] (dbg_cpu_pm_notify+0x28/0x30)
[    2.597808] [<c0111220>] (dbg_cpu_pm_notify) from [<c015f3ac>] (notifier_call_chain+0x44/0x80)
[    2.597808] [<c015f3ac>] (notifier_call_chain) from [<c0237e48>] (cpu_pm_exit+0x2c/0x54)
[    2.597808] [<c0237e48>] (cpu_pm_exit) from [<c0126ca0>] (omap_enter_idle_coupled+0x80/0x208)
[    2.597808] [<c0126ca0>] (omap_enter_idle_coupled) from [<c0680d80>] (cpuidle_enter_state+0x118/0x4ac)
[    2.597808] [<c0680d80>] (cpuidle_enter_state) from [<c0682e54>] (cpuidle_enter_state_coupled+0x3a8/0x40c)
[    2.597839] [<c0682e54>] (cpuidle_enter_state_coupled) from [<c0190c04>] (do_idle+0x1a4/0x218)
[    2.597839] [<c0190c04>] (do_idle) from [<c0190ffc>] (cpu_startup_entry+0x18/0x1c)
[    2.597839] [<c0190ffc>] (cpu_startup_entry) from [<c0c00c40>] (start_kernel+0x35c/0x3d4)
[    2.597839] [<c0c00c40>] (start_kernel) from [<8000807c>] (0x8000807c)

This RCU warning, however, is suppressed by lockdep_off() in printk().
lockdep_off() increments the ->lockdep_recursion counter and thus
disables RCU_LOCKDEP_WARN() and debug_lockdep_rcu_enabled(), which
want lockdep to be enabled "current->lockdep_recursion == 0".

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Tony Lindgren <tony@atomide.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Cc: <stable@vger.kernel.org> [3.4+]
---
 kernel/printk/printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 7180088cbb23..34da86e73d00 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1563,7 +1563,7 @@ static void call_console_drivers(const char *ext_text, size_t ext_len,
 {
 	struct console *con;
 
-	trace_console(text, len);
+	trace_console_rcuidle(text, len);
 
 	if (!console_drivers)
 		return;
-- 
2.11.1

             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-17  1:59 Sergey Senozhatsky [this message]
2017-02-17  2:18 ` Steven Rostedt
2017-02-17  3:47 ` Paul E. McKenney

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170217015932.11898-1-sergey.senozhatsky@gmail.com \
    --to=sergey.senozhatsky.work@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=rmk@armlinux.org.uk \
    --cc=rostedt@goodmis.org \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=stable@vger.kernel.org \
    --cc=tglx@linutronix.de \
    --cc=tony@atomide.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git