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Thu, 09 Jul 2020 01:33:25 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Thu, 9 Jul 2020 17:33:23 +0900 To: kernel test robot Cc: John Ogness , Petr Mladek , Peter Zijlstra , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Paul McKenney , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, lkp@lists.01.org Subject: Re: [printk] 18a2dc6982: ltp.kmsg01.fail Message-ID: <20200709083323.GA572@jagdpanzerIV.localdomain> References: <20200707145932.8752-5-john.ogness@linutronix.de> <20200709071411.GR3874@shao2-debian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200709071411.GR3874@shao2-debian> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/07/09 15:14), kernel test robot wrote: [..] Took me a while to find the FAIL-ed test: > kmsg01.c:393: INFO: TEST: read returns EPIPE when messages get overwritten > kmsg01.c:398: INFO: first seqno: 0 > kmsg01.c:411: INFO: first seqno now: 881 > kmsg01.c:425: FAIL: read returned: 77: SUCCESS (0) So this is seq number related https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/logging/kmsg/kmsg01.c#L383 LTP writes a gazillion (roughly, maybe a bit less than that) filler messages to /dev/kmsg in order to cause logbuf overlap: ... 19490 [ 172.301584] LTP kmsg01 FILLER MESSAGE TO OVERWRITE OTHERS 19491 [ 172.308730] LTP kmsg01 FILLER MESSAGE TO OVERWRITE OTHERS 19492 [ 172.313852] LTP kmsg01 FILLER MESSAGE TO OVERWRITE OTHERS 19493 [ 172.320988] LTP kmsg01 FILLER MESSAGE TO OVERWRITE OTHERS 19494 [ 172.325618] LTP kmsg01 FILLER MESSAGE TO OVERWRITE OTHERS ... -ss