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Device driver over network
by Max Ruttenberg Dec. 19, 2017

Dec. 19, 2017

Hi all, I have two compute nodes on a machine that are both running embedded Linux. The nodes are connected to each other over Ethernet. The both have an i2c bus. Node A has a thermal sensor. Node B has three fans. Right now I have a user space application running on node B that uses ssh to read from node A's thermal sensor and then adjust the fan speeds accordingly. I am wondering if there's away instead to have a hwmon driver running on Node B for the thermal monitor running on node A. This way I could get rid of the user space application and replace it with something a little bit more standard like thermald. Is this something that people have done? Maybe if not this specifically, how about a driver for a device over the network? -- Max Ruttenberg, Member of the Technical Staff Emu Technology 270 W 39th St. #1302 New York, NY 10018

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Facing problem with mutt for replying or sending mails to linux kernel mailing list
by Pravin Shedage Dec. 18, 2017

Dec. 18, 2017

Hi Everyone, Sending mail from mutt failed Error: *SMTP session failed: 501 5.5.4 https://support.google.com/mail/?p=helo <https://support.google.com/mail/?p=helo> a67sm14180316pgc.5 - gsmtp* I follow the instructions from https://kernelnewbies.org/FirstKernelPatch http://elixir.free-electrons.com/linux/latest/source/Documentation/process/… to setup environments and send patch to linux kernel for review. Mutt able to fetch mail from my gmail mail box but sending mail fails with following error: *SSL/TLS connection using TLS1.2 (ECDHE-RSA/AES-128-GCM/AEAD)-- Mutt: Compose [Approx. msg size: 0.1K Atts: 1]-------------------------------------------------------------------------------------------SMTP session failed: 501 5.5.4 https://support.google.com/mail/?p=helo <https://support.google.com/mail/?p=helo> a67sm14180316pgc.5 - gsmtp* krishna@krishna-pc:~$ *tail -f /var/log/mail.log* Dec 9 01:01:03 krishna-pc sm-msp-queue[15372]: unable to qualify my own domain name (krishna-pc) -- using short name Dec 9 01:20:01 krishna-pc sm-msp-queue[16297]: My unqualified host name (krishna-pc) unknown; sleeping for retry Dec 9 09:32:48 krishna-pc sm-mta[2043]: starting daemon (8.15.2): SMTP+queueing@00:10:00 Dec 9 09:32:49 krishna-pc sm-msp-queue[1325]: unable to qualify my own domain name (krishna-pc) -- using short name Dec 9 09:40:01 krishna-pc sm-msp-queue[3338]: My unqualified host name (krishna-pc) unknown; sleeping for retry krishna@krishna-pc:~$ *Following are my configuration which is setup on * krishna@krishna-pc:~$ *lsb_release -a* No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.3 LTS Release: 16.04 Codename: xenial krishna@krishna-pc:~$ *uname -a* Linux krishna-pc 4.10.0-42-generic #46~16.04.1-Ubuntu SMP Mon Dec 4 15:57:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux krishna@krishna-pc:~$ krishna@krishna-pc:~$ *cat ~/.muttrc* set sendmail="/usr/bin/esmtp" set realname = "Pravin Shedge" set from = "pravin.shedge4linux(a)gmail.com" set use_from = yes set envelope_from = yes set edit_headers = yes set smtp_url = 'smtps://pravin.shedge4linux@gmail.com@smtp.gmail.com' set smtp_pass = '****' set imap_user = 'pravin.shedge4linux(a)gmail.com' set imap_pass = '****' set folder = 'imaps://imap.gmail.com/' set spoolfile = +INBOX set ssl_force_tls = yes #set ssl_starttls = yes # ## G to get mail #bind index G imap-fetch-mail set editor = "vi" set edit_headers = yes # See the headers when editing set charset = UTF-8 # value of $LANG; also fallback for send_charset set send_charset="us-ascii:utf-8" set record="" set postponed="+[Gmail]/Drafts" set mbox="imaps://imap.gmail.com/[Gmail]/All Mail" set trash="imaps://imap.gmail.com/[Gmail]/Trash" # Sender, email address, and sign-off line must match # unset use_domain # because joe@localhost is just embarrassing #set include=ask-yes #set print=ask-yes #set postpone=ask-yes #set postponed = "imaps://imap.gmail.com/[Gmail]/Drafts" #set header_cache = "~/.mutt/cache/headers" #set message_cachedir = "~/.mutt/cache/bodies" #set certificate_file = "~/.mutt/certificates" #set move = no #set imap_keepalive = 900 #set imap_passive krishna@krishna-pc:~$ krishna@krishna-pc:~$* cat .gitconfig* [user] email = pravin.shedge4linux(a)gmail.com name = Pravin Shedge [sendemail] smtpencryption = tls smtpserver = smtp.gmail.com smtpuser = pravin.shedge4linux(a)gmail.com smtpserverport = 587 smtppass = "****" krishna@krishna-pc:~$* cat ~/.esmtprc* identity "pravin.shedge4linux(a)gmail.com" hostname smtp.gmail.com:587 username "pravin.shedge4linux(a)gmail.com" password "****" starttls required krishna@krishna-pc:~$ *tail -f /var/log/syslog* Dec 9 10:40:01 krishna-pc CRON[4755]: (smmsp) CMD (test -x /etc/init.d/sendmail && test -x /usr/share/sendmail/sendmail && test -x /usr/lib/sm.bin/sendmail && /usr/share/sendmail/sendmail cron-msp) Dec 9 10:44:30 krishna-pc systemd-timesyncd[609]: Timed out waiting for reply from [2001:67c:1560:8003::c7]:123 (ntp.ubuntu.com) Dec 9 10:45:01 krishna-pc CRON[4831]: (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1) krishna@krishna-pc:~$ krishna@krishna-pc:~$* cat /etc/resolv.conf* # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.1.1 search photonmax3g.wifi krishna@krishna-pc:~$ krishna@krishna-pc:~$* ip addr* 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000 link/ether 00:26:2d:74:82:d3 brd ff:ff:ff:ff:ff:ff 3: wlp4s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 90:4c:e5:56:c5:a0 brd ff:ff:ff:ff:ff:ff 5: enx001e101f0000: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:1e:10:1f:00:00 brd ff:ff:ff:ff:ff:ff inet 192.168.1.100/24 brd 192.168.1.255 scope global dynamic enx001e101f0000 valid_lft 86387sec preferred_lft 86387sec inet6 fe80::8fff:8915:878b:1b6b/64 scope link valid_lft forever preferred_lft forever krishna@krishna-pc:~$ cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.1.1 search photonmax3g.wifi krishna@krishna-pc:~$* cat /etc/hosts* 127.0.0.1 localhost 127.0.0.1 krishna-pc # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters krishna@krishna-pc:~$ Do I missing something ? Please let me know.... Thanks & Regards PraviN +919156991946

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submitting a patch for a stable tree
by Martin Kaiser Dec. 18, 2017

Dec. 18, 2017

Dear all, I tried to submit a patch for 4.14 that was already accepted upstream and is in linux-next and the 4.15-rcs. To understand how this should be done, I looked at https://www.kernel.org/doc/html/v4.14/process/stable-kernel-rules.html and tried to follow Option 2. It looks like I didn't get it right. I started with a tree that contains the patch and ran git format-patch -1 <commit id> and then git send-email --to stable(a)verg.kernel.org \ --cc <the original maintainer and reviewers> \ --annotate <patch file> I added the upstream commit id above the original commit message and a tag line Cc: <stable(a)vger.kernel.org> # 4.14.x to the patch and sent it out. Is there anything that's wrong or missing? Is there a mailing list archive for stable(a)vger.kernel.org where I can have a look at correct submissions and check that my submission made it to the list? Thanks for your help, Martin

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why this field is taskstats. ac_sched is specifically aligned as 8?
by Shiyao MA Dec. 15, 2017

Dec. 15, 2017

Hi, http://elixir.free-electrons.com/linux/latest/source/include/uapi/linux/tas… Why the field is taskstats. ac_sched aligned as 8 ? -- Best, Shiyao

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Shared DDR RAM access on AMP system
by Edward Wingate Dec. 14, 2017

Dec. 14, 2017

On a dual-core ARM SOC (Zynq7020), I have Linux running on core0 and an RTOS running on core1. I share data between the two cores with a 4MB block of DDR RAM that I've marked in the MMU as shareable and non-cacheable. I use an entry in the device tree and the uio_pdrv_genirq driver to create an uio device (/dev/uio0) in Linux. With this device, I can use mmap to read/write the block of DDR RAM from Linux. Even though it's meant for memory mapped devices, the uio_pdrv_genirq driver seems to work for accessing shared DDR RAM. Are there any potential issues that may arise from using this driver for accessing shared DDR RAM? Is the uio_dmem_genirq driver more appropriate for this? I couldn't get it to work though, perhaps because of this bug: https://forums.xilinx.com/t5/Embedded-Linux/Bug-in-uio-dmem-genirq-UIO-driv… Thanks for any advice/help. Ed

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hrtimer_interrupt time sync issues across cores
by Rajasekaran Chandrasekaran Dec. 14, 2017

Dec. 14, 2017

Hi, In our multi-core x86 based system that is running 3.4.19 version of kernel, hrtimer_interrupt (called from apic_timer_interrupt) keeps looping in hardirq for atleast 1.6 seconds. We use tsc as our clock source. The issue happens very rarely in our system and hard to reproduce. Problem: Inside hrtimer_interrupt function, basenow.tv64 in CPU-3 is 1.6 seconds ahead of other CPU’s (we have 4 cores), whereas hrtimer->_softexpires.tv64 is in sync with remaining CPU’s. Due to this, the if condition inside hrtimer_interrupt where we check if basenow.tv64 < hrtimer_get_softexpires_tv64(timer) is not true for 1.6 seconds, which cause the while loop inside hrtimer_interrupt to not exit. Below is the ftrace captured during the problem. <idle>-0 [002] d.h. 800364.533632: hrtimer_expire_entry: hrtimer=ffff88017fd0c960 function=tick_sched_timer now=801616439840902 ksoftirqd/3-19 [003] dNh. 800364.539178: hrtimer_expire_entry: hrtimer=ffff88017fd8c960 function=tick_sched_timer now=801618042768641 ksoftirqd/3-19 [003] dNh. 800364.539185: hrtimer_start: hrtimer=ffff88017fd8c960 function=tick_sched_timer expires=801616446505014 softexpires=801616446505014 As we can see, the difference in now time between CPU-2 and CPU-3(where the time jump is seen) is significant. Ftrace indicates that the now time has drifted apart in CPU-3 by 1602 milliseconds, even though timestamp is apart by only 6 milliseconds. Also since the hrtimer expiry time is in the past, we end up spending lot of time in hardirq. From my understanding of the code, , basenow.tv64 is computed in hrtimer_update_base() ->ktime_get_update_offsets() as timekeeper.xtime – offs_real. Both timekeeper.xtime and offs_real are always updated under a lock. So, I am still unsure on how only one core is seeing the time incorrectly. Any inputs will be greatly help. Thanks, Raj

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Virtual Memory map
by Damian Tometzki Dec. 13, 2017

Dec. 13, 2017

Hello all, i have a short question: How are the bits (in brackets) calculated in the virtual memory map ? for example the first line (=47 bits) Virtual memory map with 4 level page tables: 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm hole caused by [47:63] sign extension ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor Best regards Damian

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Virtual Memory Map
by Damian Tometzki Dec. 12, 2017

Dec. 12, 2017

Hello all, i have a short question: How are the bits (in brackets) calculated in the virtual memory map ? for example the first line (=47 bits) Virtual memory map with 4 level page tables: 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm hole caused by [47:63] sign extension ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor Best regards Damian

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Re: sched_child_runs_first doesn't work
by strongbox8 Dec. 11, 2017

Dec. 11, 2017

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Header organization/separation rule in kernel
by Shiyao MA Dec. 10, 2017

Dec. 10, 2017

Hi, I wonder the header separation rule in kernel. To make this question concrete, for example, let's targeting genetlink.h It can be found in: http://elixir.free-electrons.com/linux/latest/source/include/net/genetlink.h http://elixir.free-electrons.com/linux/latest/source/include/linux/genetlin… http://elixir.free-electrons.com/linux/latest/source/include/uapi/linux/gen… so basically three parts, in uapi, linux/genetlink.h, and net/genetlink.h. I understand the necessity of uapi, but why divide the genetlink.h in linux and the net folder? What's the benefit of such separation? -- Best, Shiyao

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