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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Petr Mladek <pmladek@suse.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	syzkaller <syzkaller@googlegroups.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Fengguang Wu <fengguang.wu@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] printk: inject caller information into the body of message
Date: Wed, 20 Jun 2018 20:19:36 +0900
Message-ID: <20180620111936.GE444@jagdpanzerIV> (raw)
In-Reply-To: <CACT4Y+a6nUqdpSyYGGcXKAgVbcw+uQOz2kYx8tUS+8T5-bzqkg@mail.gmail.com>

On (06/20/18 11:30), Dmitry Vyukov wrote:
> 
> https://gist.githubusercontent.com/dvyukov/1528e86e5139f2fd1bf9902398d48298/raw/3b42148554eefed210f1e626d5befd50405c5487/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/6e08ac521f3e19534970ed97aeee1603/raw/0f0bb361902de94e7ee331ac500a3ceebf812c22/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/6e9db2313e48773ad1cd861da8020008/raw/d5b7c023fc8a38c72b1cf8bb1da85fb1c31cea5f/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/3d1bda4c690414ac027de1da45759751/raw/2c68980eabf4f6be24060e807a75f2d3570b5a42/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/9b8831e9ac73ffafa111a33ad40c5667/raw/f4097fbea8f89b25a282a6ef7e648145e10ae4b7/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/d78a3187a1b4e004820e92efcb16f9e0/raw/5530bcbf009c3fba3c581b2d24c523c673c6ef12/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/da1e42436af9ad2afc7de49f2d503510/raw/7dd4cbcc651c5b87122f066a3c689999ae8c4121/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/4571b94bd8cbd78d759412c560fa395c/raw/964c73fc993fc8a9000571e0b7618000584f3638/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/b6deac5faa958ae3733413b34dd5feed/raw/c4da219e284f7fc55da8c3c3af623a87f31bf653/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/2f54c6a2e45347ea76d9c5ce3c0ff091/raw/45f4873898ec8e0d9aa16b9c5c63a85410fd05e0/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/96cb39e29124dbbe2a65a91ec7a5639e/raw/aa8f7b2b1dfa5b8bb8cf93d8a821ca9938e8fc54/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/424da8282d5b28f8be10eab595d37444/raw/acc2fb1ececc1ea9a8215213f7e37e08b524c096/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/b07f37720c632d6d56ae67d95e5599b3/raw/8624ba47d6eb4e7d4d58e3ae1242ebe6cc46d361/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/bc24a7b92289ec04587fb29fc1085045/raw/3136e9262ee2233b5ab369a4a82e83953fc2d8a2/gistfile1.txt


Just a small remark

I randomly picked some links, and at least in several reports I saw:

** 4495 printk messages dropped ** [   50.830930]  [<ffffffff8123ab47>] do_raw_write_lock+0xc7/0x1d0
** 3816 printk messages dropped ** [   50.839887]  [<ffffffff814fb353>] SyS_read+0xd3/0x1c0
** 3497 printk messages dropped ** [   50.848107]  [<ffffffff81003044>] ? lockdep_sys_exit_thunk+0x12/0x14
** 4057 printk messages dropped ** [   50.857615] 	run_ksoftirqd+0x20/0x60
** 2855 printk messages dropped ** [   50.864318]  [<ffffffff814fb353>] SyS_read+0xd3/0x1c0
** 3490 printk messages dropped ** [   50.872518]  [<ffffffff815bee10>] ? fsnotify+0xe40/0xe40
** 3600 printk messages dropped ** [   50.880974] 	SyS_fcntl+0x5be/0xc70

This will not get any better if we have printk context tracking. The
problem here is that we lose messages: your console is significantly slower
than your CPUs. So while one CPU is doing its best printing pending logbuf
messages to a slow console, the rest of CPUs don't hesitate to append new
messages (printk -> log_store). Since logbuf is limited in size - we wrap
around and this results in lost messages.

	-ss

  reply index

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <201804232233.CIC65675.OJSOMFQOFFHVtL@I-love.SAKURA.ne.jp>
     [not found] ` <CACT4Y+boyw_Qy=y-iTnsKZrtTgF0Hk3nHN_xtqUdX4etgiYDQw@mail.gmail.com>
2018-04-24  1:33   ` printk feature for syzbot? Sergey Senozhatsky
2018-04-24 14:40     ` Steven Rostedt
2018-04-26 10:06     ` Petr Mladek
2018-05-10  4:22       ` Sergey Senozhatsky
2018-05-10 11:30         ` Petr Mladek
2018-05-10 12:11           ` Sergey Senozhatsky
2018-05-10 14:22             ` Steven Rostedt
2018-05-10 14:50         ` Tetsuo Handa
2018-05-11  1:45           ` Sergey Senozhatsky
     [not found]             ` <201805110238.w4B2cIGH079602@www262.sakura.ne.jp>
2018-05-11  6:21               ` Sergey Senozhatsky
2018-05-11  9:17                 ` Dmitry Vyukov
2018-05-11  9:50                   ` Sergey Senozhatsky
2018-05-11 11:58                     ` [PATCH] printk: inject caller information into the body of message Tetsuo Handa
2018-05-17 11:21                       ` Sergey Senozhatsky
2018-05-17 11:52                         ` Sergey Senozhatsky
2018-05-18 12:15                         ` Petr Mladek
2018-05-18 12:25                           ` Dmitry Vyukov
2018-05-18 12:54                             ` Petr Mladek
2018-05-18 13:08                               ` Dmitry Vyukov
2018-05-24  2:21                                 ` Sergey Senozhatsky
2018-05-23 10:19                           ` Tetsuo Handa
2018-05-24  2:14                           ` Sergey Senozhatsky
2018-05-26  6:36                             ` Dmitry Vyukov
2018-06-20  5:44                               ` Dmitry Vyukov
2018-06-20  8:31                                 ` Sergey Senozhatsky
2018-06-20  8:45                                   ` Dmitry Vyukov
2018-06-20  9:06                                     ` Sergey Senozhatsky
2018-06-20  9:18                                       ` Sergey Senozhatsky
2018-06-20  9:31                                         ` Dmitry Vyukov
2018-06-20 11:07                                           ` Sergey Senozhatsky
2018-06-20 11:32                                             ` Dmitry Vyukov
2018-06-20 13:06                                               ` Sergey Senozhatsky
2018-06-22 13:06                                                 ` Tetsuo Handa
2018-06-25  1:41                                                   ` Sergey Senozhatsky
2018-06-25  9:36                                                     ` Dmitry Vyukov
2018-06-27 10:29                                                       ` Tetsuo Handa
2018-09-10 11:20                                                 ` Alexander Potapenko
2018-09-12  6:53                                                   ` Sergey Senozhatsky
2018-09-12 16:05                                                     ` Steven Rostedt
2018-09-13  7:12                                                       ` Sergey Senozhatsky
2018-09-13 12:26                                                         ` Petr Mladek
2018-09-13 14:28                                                           ` Sergey Senozhatsky
2018-09-14  1:22                                                             ` Steven Rostedt
2018-09-14  2:15                                                               ` Sergey Senozhatsky
2018-09-14  6:57                                                             ` Sergey Senozhatsky
2018-09-14 10:37                                                               ` Tetsuo Handa
2018-09-14 11:50                                                                 ` Sergey Senozhatsky
2018-09-14 12:03                                                                   ` Tetsuo Handa
2018-09-14 12:22                                                                     ` Sergey Senozhatsky
2018-09-19 11:02                                                                       ` Tetsuo Handa
2018-09-24  8:11                                                                         ` Tetsuo Handa
2018-09-27 16:10                                                                           ` Tetsuo Handa
2018-09-28  9:02                                                                             ` Sergey Senozhatsky
2018-09-28  9:09                                                                           ` Sergey Senozhatsky
2018-09-28 11:01                                                                             ` Tetsuo Handa
2018-09-29 10:51                                                                               ` Sergey Senozhatsky
2018-09-29 11:15                                                                                 ` Tetsuo Handa
2018-10-01  2:37                                                                                   ` Sergey Senozhatsky
2018-10-01  2:58                                                                                     ` Sergey Senozhatsky
2018-10-01 11:21                                                                                     ` Tetsuo Handa
2018-10-02  6:38                                                                                       ` Sergey Senozhatsky
2018-10-08 10:31                                                                                         ` Tetsuo Handa
2018-10-08 16:03                                                                                           ` Petr Mladek
2018-10-08 20:48                                                                                             ` Tetsuo Handa
2018-10-09 14:52                                                                                               ` Petr Mladek
2018-10-09 21:19                                                                                                 ` Tetsuo Handa
2018-10-10 10:14                                                                                                   ` Tetsuo Handa
2018-10-11 10:20                                                                                                     ` Tetsuo Handa
2018-10-11 13:47                                                                                                       ` Steven Rostedt
2018-10-08 15:43                                                                                         ` Petr Mladek
2018-09-28  8:56                                                                         ` Sergey Senozhatsky
2018-09-28 11:21                                                                           ` Tetsuo Handa
2018-09-29 11:13                                                                             ` Sergey Senozhatsky
2018-09-29 11:39                                                                               ` Tetsuo Handa
2018-10-01  5:52                                                                               ` Sergey Senozhatsky
2018-10-01  8:37                                                                                 ` Sergey Senozhatsky
2018-10-01 18:06                                                                               ` Steven Rostedt
2018-09-14  1:12                                                         ` Steven Rostedt
2018-09-14  1:55                                                           ` Sergey Senozhatsky
2018-06-21  8:29                                               ` Sergey Senozhatsky
2018-06-20  9:30                                       ` Dmitry Vyukov
2018-06-20 11:19                                         ` Sergey Senozhatsky [this message]
2018-06-20 11:25                                           ` Dmitry Vyukov
2018-06-20 11:37                                         ` Fengguang Wu
2018-06-20 12:31                                           ` Dmitry Vyukov
2018-06-20 12:41                                             ` Fengguang Wu
2018-06-20 12:45                                               ` Dmitry Vyukov
2018-06-20 12:48                                                 ` Fengguang Wu
2018-05-11 13:37                     ` printk feature for syzbot? Steven Rostedt
2018-05-15  5:20                       ` Sergey Senozhatsky
2018-05-15 14:39                         ` Steven Rostedt
2018-05-11 11:02                 ` [PATCH] printk: fix possible reuse of va_list variable Tetsuo Handa
2018-05-11 11:27                   ` Sergey Senozhatsky
2018-05-17 11:57                   ` Petr Mladek

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