Messages in this thread | | | From | xiang xiao <> | Date | Thu, 14 Feb 2019 00:25:56 +0800 | Subject | Re: [PATCH] printk: add KERN_NOTIME to skip the timestamp |
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On Wed, Feb 13, 2019 at 10:31 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Wed, 13 Feb 2019 22:00:04 +0800 > xiang xiao <xiaoxiang781216@gmail.com> wrote: > > > On Wed, Feb 13, 2019 at 9:47 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > On Wed, 13 Feb 2019 14:19:01 +0800 > > > xiang xiao <xiaoxiang781216@gmail.com> wrote: > > > > > > > On Wed, Feb 13, 2019 at 3:46 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > > > > > On Wed, 13 Feb 2019 02:11:05 +0800 > > > > > Xiang Xiao <xiaoxiang781216@gmail.com> wrote: > > > > > > > > > > > Because log may already add the timestamp sometime > > > > > > > > > > Can you be a bit more detailed on this. When and where does this > > > > > happen? > > > > > > > > Here is my case: > > > > 1.A small MCU(Cortex M4) in SoC run RTOS > > > > 2.RTOS append timestamp to log for the accurate timing > > > > 3.RTOS send log to Linux kernel when buffer exceed the threshold > > > > 4.Kernel call printk to dump the received buffer > > > > So I want that printk skip the timestamp here. > > > > > > > > > If anything, I would probably prefer that we export whether > > > > > time is being printed, and have the caller not print time if printk is > > > > > doing it already, than to add the complexity into printk itself. > > > > > > > > Actually, the timestamp of our initial implementation like your > > > > suggestion come from printk, > > > > but we found that timestamp from kernel isn't accurate as from RTOS > > > > due the buffer and IPC. > > > > > > > > > > If the timestamps are different, then you don't want to remove the > > > printk one. Otherwise you are going to have a confusion between your > > > added timestamp mixed in with the kernel's inaccurate timestamps. > > > > > > > Here is a sample output with this patch: > > [ 10.991426] virtio_rpmsg_bus virtio1: rpmsg host is online > > [ 10.991443] remoteproc remoteproc1: registered virtio1 (type 7) > > [ 10.991450] remoteproc remoteproc1: remote processor > > f9210000.toppwr:sen-rproc is now up > > [ 10.993715] virtio_rpmsg_bus virtio1: creating channel > > rpmsg-ttySENSOR addr 0x1 > > [ 10.994606] virtio_rpmsg_bus virtio1: creating channel rpmsg-ttyGPS addr 0x2 > > [ 10.995236] virtio_rpmsg_bus virtio1: creating channel rpmsg-clk addr 0x3 > > [ 10.995702] virtio_rpmsg_bus virtio1: creating channel rpmsg-syslog addr 0x4 > > [ 10.996197] virtio_rpmsg_bus virtio1: creating channel rpmsg-rtc addr 0x5 > > [ 10.997297] virtio_rpmsg_bus virtio1: creating channel rpmsg-hostfs addr 0x6 > > [ 10.999842] virtio_rpmsg_bus virtio1: creating channel rpmsg-usrsock addr 0x7 > > [ 0.007680] sensor: NuttX sensor 7.28 e3c2ecb Feb 12 2019 16:53:49 > > arm song/banks > > ^^^^^^^^^^^^^ > > [ 11.918177] random: crng init done > > [ 12.567362] e2fsck: e2fsck 1.42.9 (28-Dec-2013) > > > > Without this patch: > > [ 10.991426] virtio_rpmsg_bus virtio1: rpmsg host is online > > [ 10.991443] remoteproc remoteproc1: registered virtio1 (type 7) > > [ 10.991450] remoteproc remoteproc1: remote processor > > f9210000.toppwr:sen-rproc is now up > > [ 10.993715] virtio_rpmsg_bus virtio1: creating channel > > rpmsg-ttySENSOR addr 0x1 > > [ 10.994606] virtio_rpmsg_bus virtio1: creating channel rpmsg-ttyGPS addr 0x2 > > [ 10.995236] virtio_rpmsg_bus virtio1: creating channel rpmsg-clk addr 0x3 > > [ 10.995702] virtio_rpmsg_bus virtio1: creating channel rpmsg-syslog addr 0x4 > > [ 10.996197] virtio_rpmsg_bus virtio1: creating channel rpmsg-rtc addr 0x5 > > [ 10.997297] virtio_rpmsg_bus virtio1: creating channel rpmsg-hostfs addr 0x6 > > [ 10.999842] virtio_rpmsg_bus virtio1: creating channel rpmsg-usrsock addr 0x7 > > [ 11.105345][ 0.007680] sensor: NuttX sensor 7.28 e3c2ecb Feb 12 > > 2019 16:53:49 arm song/banks > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > [ 11.918177] random: crng init done > > [ 12.567362] e2fsck: e2fsck 1.42.9 (28-Dec-2013) > > > > Which one do you think better? > > Honestly, the one without the patch. > > Seriously, it also makes it easy to see where that message happened > with respect to the other printks. With your patch, we would have no > idea, and if I was a normal user, unaware of this patch, I would > probably submit a bug report claiming that something is wrong with the > timestamps. >
Ok, I will remove KERN_NOTIME from rpmsg-syslog driver.
> -- Steve
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