The patch titled
Subject: printk: use rcuidle console tracepoint
has been added to the -mm tree. Its filename is
printk-use-rcuidle-console-tracepoint.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/printk-use-rcuidle-console-tracepoint.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/printk-use-rcuidle-console-tracepoint.patch
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From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Subject: printk: use rcuidle console tracepoint
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".
Link: http://lkml.kernel.org/r/20170217015932.11898-1-sergey.senozhatsky@xxxxxxxxx
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Reported-by: Tony Lindgren <tony@xxxxxxxxxxx>
Tested-by: Tony Lindgren <tony@xxxxxxxxxxx>
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tony Lindgren <tony@xxxxxxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.4+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/printk/printk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN kernel/printk/printk.c~printk-use-rcuidle-console-tracepoint kernel/printk/printk.c
--- a/kernel/printk/printk.c~printk-use-rcuidle-console-tracepoint
+++ a/kernel/printk/printk.c
@@ -1516,7 +1516,7 @@ static void call_console_drivers(int lev
{
struct console *con;
- trace_console(text, len);
+ trace_console_rcuidle(text, len);
if (!console_drivers)
return;
_
Patches currently in -mm which might be from sergey.senozhatsky.work@xxxxxxxxx are
printk-use-rcuidle-console-tracepoint.patch
zram-remove-obsolete-sysfs-attrs.patch