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Fri, 25 Sep 2020 19:38:51 +0000 (GMT) Subject: Re: [PATCH printk v5 6/6] printk: reimplement log_cont using record extension From: Marek Szyprowski To: John Ogness , Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , Peter Zijlstra , Andrea Parri , Paul McKenney , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Message-ID: Date: Fri, 25 Sep 2020 21:38:51 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Transfer-Encoding: 8bit Content-Language: en-US X-Brightmail-Tracker: H4sIAAAAAAAAA01Sa1BMYRieb8/Zc047rflsaV80GTvDDEYXZZxBN8w4Lj/8yRhG2XQktRu7 5fpDpCY7yQpDG7ZVpstUSxG2qai0Xca6JJGMVJMRFV0MyaXTKfr3vM/zvN/7Pu98DKHokM5h orRxvE6rjlFRMrKs7odj6eb12jDvl9dXsonZVoote2FGbHnTiIRttl2h2JpzFsQO5nwjWfuZ BxL2T9eIlK1M6ZCwncZ0CVs01EWzpSUXCbYzrY8OknP3TW9p7lRlG82V5i3mSgpOU1y/w0Fz 9Zd/klzV1cJxPuc4Z73dQnJDJR5bZNtlqyP4mKiDvM4rYJdsb0NzP7m/T3m41JBJJSC7iwE5 MYD94Fbad8KAZIwC5yGw9o9KBUGBhxG0XpoUhhDYbTfJqY78tEdSUchFkPLxnUQsBhCcvjM8 XjCMC94GxYWzhQYK+4Chz0AJ2BVvgoJPFbTgJ/AzAoqulUsEQY4DoMXYgwRM4gVw803lxLRZ OBTqGjtJ0TMTGjK6J7ATDoSXFuPEowSeB4l3MgkRK6Gt2zyxEOAkBuxfeybXXgemFAslYhfo td+mRewOTedTSbEhEcF7RxEtFqkImk9eRqJrFbQ7RikhGoEXgdXmJdLB4LDaSIEGPANe9c0U l5gB6WXC7QRaDinJCtG9EEz24n9jHz59ThiRyjQtmmlaHNO0OKb/c7MQWYCUfLxeE8nrfbX8 IU+9WqOP10Z67o7VlKDxf9f02z5yD1WOhVcjzCCVs7y+UxOmkKoP6o9oqhEwhMpVvuZxU6hC HqE+cpTXxYbp4mN4fTWay5Aqpdz3+sedChypjuOjeX4/r5tSJYzTnAQUdyK9bnn2rSjLDv9X n46BsmDjk8zPwUkJLR7FuRYzteGA6+jyJTZj8pjidXZIyFpfv9YA7xrlNeezK7eMyW8E3m30 6c3oqv91wfzFPz8rKPiDOWOFe4Quetna+a37yt3ssvZj8/0cA275LeGbWmtytrK5QbX08aDB uXtw/+raiqNVKlK/V+2zmNDp1X8BCPBno3MDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrMIsWRmVeSWpSXmKPExsVy+t/xe7o+7nnxBtceMFk0L17PZrHtynxG i92nvzJZXN41h83i8MSFjBaflnxjsTjee4DJ4v/jr6wW+zqAih9NmMRksfbzY3aLzZumMls8 6nvL7sDrsXPWXXaPln232D02r9Dy2LSqk83j3blz7B4nZvxm8dg/dw1QfEm9x/otV1k8Pm+S C+CK0rMpyi8tSVXIyC8usVWKNrQw0jO0tNAzMrHUMzQ2j7UyMlXSt7NJSc3JLEst0rdL0Ms4 efkdS8Fb8YrNXbPZGhiPC3cxcnJICJhIrOw7ytrFyMUhJLCUUaLj+V5miISMxMlpDawQtrDE n2tdbBBFbxklNpy6z9LFyMEhLBAhsW6NJEgNm4ChRNdbkBpODhEBb4lVr/eyg9QzC1xmlnj1 Yik7RPMSRokdp/+xgFTxCthJXJ3wjBHEZhFQldhwex9YXFQgTuJMzws2iBpBiZMzn4DFOQXs Ja4tnAAWZxYwk5i3+SEzhC0v0bx1NpQtLnHryXymCYxCs5C0z0LSMgtJyywkLQsYWVYxiqSW Fuem5xYb6RUn5haX5qXrJefnbmIERvi2Yz+37GDsehd8iFGAg1GJh1fhaW68EGtiWXFl7iFG CQ5mJRFep7On44R4UxIrq1KL8uOLSnNSiw8xmgI9N5FZSjQ5H5h88kriDU0NzS0sDc2NzY3N LJTEeTsEDsYICaQnlqRmp6YWpBbB9DFxcEo1ME6omjq3v+bjgzdNV7svidQo+98TNJpSWa3g lXJKYpHWw0f7vz/Pnet+t+p0/TpLK/c+bevlLHt8lXt330sNWv5y+rf7mx6c8NJcZiVhcmKF 1dlnlx6Hud2/IyDwRkje5YqeRMc00/NP913eMN/F2zTv+xuttguHYmtOm0p7bZoY36CXoPEo 31aJpTgj0VCLuag4EQCoHt9oBgMAAA== X-CMS-MailID: 20200925193852eucas1p10c459f3f90192c1079f8a8f04b872015 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20200925193852eucas1p10c459f3f90192c1079f8a8f04b872015 X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20200925193852eucas1p10c459f3f90192c1079f8a8f04b872015 References: <20200914123354.832-1-john.ogness@linutronix.de> <20200914123354.832-7-john.ogness@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi again, On 25.09.2020 21:08, Marek Szyprowski wrote: > Hi John, > > On 14.09.2020 14:33, John Ogness wrote: >> Use the record extending feature of the ringbuffer to implement >> continuous messages. This preserves the existing continuous message >> behavior. >> >> Signed-off-by: John Ogness >> Reviewed-by: Petr Mladek > > This patch landed recently in linux-next as commit f5f022e53b87 > ("printk: reimplement log_cont using record extension"). I've noticed > that it causes a regression on my test system (ARM 32bit Samsung > Exynos 4412-based Trats2 board). The messages are printed correctly on > the serial console during boot, but then when I run 'dmesg' command, > the log is truncated. > > Here is are the last lines of the dmesg log after this patch: > > [    6.649018] Waiting 2 sec before mounting root device... > [    6.766423] dwc2 12480000.hsotg: new device is high-speed > [    6.845290] dwc2 12480000.hsotg: new device is high-speed > [    6.914217] dwc2 12480000.hsotg: new address 51 > [    8.710351] RAMDISK: squashfs filesystem found at block 0 > > The corresponding dmesg lines before applying this patch: > > [    8.864320] RAMDISK: squashfs filesystem found at block 0 > [    8.868410] RAMDISK: Loading 37692KiB [1 disk] into ram disk... / > [    9.071670] / > [    9.262498] / > [    9.540711] / > [    9.818031] done. > [   10.660074] VFS: Mounted root (squashfs filesystem) readonly on > device 1:0. > [   10.739525] EXT4-fs (mmcblk0p1): INFO: recovery required on > readonly filesystem > [   10.745347] EXT4-fs (mmcblk0p1): write access will be enabled > during recovery > [   10.861129] EXT4-fs (mmcblk0p1): recovery complete > [   10.878150] EXT4-fs (mmcblk0p1): mounted filesystem with ordered > data mode. Opts: (null) > [   10.881811] VFS: Mounted root (ext4 filesystem) readonly on device > 179:49. > [   10.889858] Trying to move old root to /initrd ... > [   10.895192] okay > [   10.914411] devtmpfs: mounted > [   10.925087] Freeing unused kernel memory: 1024K > [   10.933222] Run /sbin/init as init process > [   10.941723]   with arguments: > [   10.949890]     /sbin/init > [   10.949900]   with environment: > [   10.949909]     HOME=/ > [   10.949917]     TERM=linux > [   12.415991] random: systemd-udevd: uninitialized urandom read (16 > bytes read) > [   12.425361] random: systemd-udevd: uninitialized urandom read (16 > bytes read) > [   12.438578] random: systemd-udevd: uninitialized urandom read (16 > bytes read) > > ... > > I can provide a complete logs if that helps. One more information - this issue happens only if the kernel is compiled from exynos_defconfig. If use multi_v7_defconfig, the dmesg works fine on that board. exynos_defconfig has quite a lots of debugging options enabled... Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland