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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Dmitriy Vyukov <dvyukov@google.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Alexander Potapenko <glider@google.com>,
	Fengguang Wu <fengguang.wu@intel.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Ingo Molnar <mingo@redhat.com>,
	Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages.
Date: Sat, 3 Nov 2018 11:00:10 +0900	[thread overview]
Message-ID: <80eb808d-4c17-9b1f-f866-3e22b9b2b18e@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20181102133629.GN3178@hirez.programming.kicks-ass.net>

On 2018/11/02 22:36, Peter Zijlstra wrote:
> On Fri, Nov 02, 2018 at 10:31:57PM +0900, Tetsuo Handa wrote:
>> syzbot is sometimes getting mixed output like below due to concurrent
>> printk(). Mitigate such output by using line-buffered printk() API.
>>
>>   RCU used illegally from idle CPU!
>>   rcu_scheduler_active = 2, debug_locks = 1
>>   RSP: 0018:ffffffff88007bb8 EFLAGS: 00000286
>>   RCU used illegally from extended quiescent state!
>>    ORIG_RAX: ffffffffffffff13
>>   1 lock held by swapper/1/0:
>>   RAX: dffffc0000000000 RBX: 1ffffffff1000f7b RCX: 0000000000000000
>>    #0: 
>>   RDX: 1ffffffff10237b8 RSI: 0000000000000001 RDI: ffffffff8811bdc0
>>   000000004b34587c
>>   RBP: ffffffff88007bb8 R08: ffffffff88075e00 R09: 0000000000000000
>>    (
>>   R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>>   rcu_read_lock
>>   R13: ffffffff88007c78 R14: 0000000000000000 R15: 0000000000000000
>>   ){....}
>>    arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
>>    default_idle+0xc2/0x410 arch/x86/kernel/process.c:498
>>   , at: trace_call_bpf+0xf8/0x640 kernel/trace/bpf_trace.c:46
> 
> WTH is that buffered aPI, and no, that breaks my earlyprintk stuff.
> 

This API is nothing but a wrapper for reducing frequency of directly
calling printk() by using snprintf() if possible. Thus, whatever your
earlyprintk stuff is, this API should not affect it.

  reply	other threads:[~2018-11-03  2:00 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-02 13:31 [PATCH v6 1/3] printk: Add line-buffered printk() API Tetsuo Handa
2018-11-02 13:31 ` [PATCH 2/3] mm: Use line-buffered printk() for show_free_areas() Tetsuo Handa
2018-11-07 14:07   ` Petr Mladek
2018-11-02 13:31 ` [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages Tetsuo Handa
2018-11-02 13:36   ` Peter Zijlstra
2018-11-03  2:00     ` Tetsuo Handa [this message]
2018-11-06  8:38     ` Petr Mladek
2018-11-06  9:05       ` Sergey Senozhatsky
2018-11-06 12:57         ` Petr Mladek
2018-11-06  9:56       ` Tetsuo Handa
2018-11-07 15:19   ` Petr Mladek
2018-11-08  4:45     ` Sergey Senozhatsky
2018-11-08 11:37       ` Tetsuo Handa
2018-11-09  6:12         ` Sergey Senozhatsky
2018-11-09  9:55           ` Tetsuo Handa
2018-11-09 15:43             ` Petr Mladek
2018-11-10  2:42               ` Tetsuo Handa
2018-11-23 12:46                 ` Petr Mladek
2018-11-23 13:12                   ` Tetsuo Handa
2018-11-23 15:56                   ` Steven Rostedt
2018-11-24  0:24                     ` Tetsuo Handa
2018-11-26  4:34                       ` Sergey Senozhatsky
2018-11-28 13:29                     ` David Laight
2018-11-29 10:09                       ` Tetsuo Handa
2018-11-30 16:01                         ` Petr Mladek
2018-11-10  8:52               ` Tetsuo Handa
2018-11-23 12:52                 ` Petr Mladek
2018-11-09 14:08           ` Linus Torvalds
2018-11-09 14:42             ` Steven Rostedt
2018-11-08 11:53       ` Petr Mladek
2018-11-08 12:44         ` Sergey Senozhatsky
2018-11-08 14:21           ` Sergey Senozhatsky
2018-11-09  9:54     ` Tetsuo Handa
2018-11-02 14:40 ` [PATCH v6 1/3] printk: Add line-buffered printk() API Matthew Wilcox
2018-11-03  1:55   ` Tetsuo Handa
2018-11-02 18:12 ` kbuild test robot
2018-11-02 18:12   ` kbuild test robot
2018-11-06 14:35 ` Sergey Senozhatsky
2018-11-07 10:21   ` Petr Mladek
2018-11-07 12:54     ` Tetsuo Handa
2018-11-08  2:21     ` Sergey Senozhatsky
2018-11-08 11:24       ` Petr Mladek
2018-11-08 11:46         ` Tetsuo Handa
2018-11-08 12:30         ` Sergey Senozhatsky
2018-11-09 14:10           ` Petr Mladek
2018-11-12  7:59             ` Sergey Senozhatsky
2018-11-12 10:42               ` Tetsuo Handa
2018-11-17 10:14               ` Tetsuo Handa
2018-11-07 10:52   ` Tetsuo Handa
2018-11-07 11:01     ` David Laight
2018-11-07 12:00       ` Petr Mladek
2018-11-07 11:45     ` Petr Mladek
2018-11-08  2:30     ` Sergey Senozhatsky
2018-11-07 13:41 ` Petr Mladek
2018-11-07 14:06 ` Petr Mladek

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