February 2016 - kernelnewbies@kernelnewbies.org

Does Linux kernel disables any Interrupts while going into IRQ handler?
by priyaranjan Feb. 24, 2016

Feb. 24, 2016

When an Interrupt occurs most device drivers creates a critical section using spin_lock_irqsave or spin_lock_irq which disables the interrupt. In such a case the Interrupts are disabled by the IRQ handler. My question is whether Linux kernel disables any interrupts just when the IRQ handler executes or it just wait for the IRQ handler programmer to disable the IRQ in whatever way? My understanding is that Russel King has implemented IRQ_DISABLED, If this flag is set then only the IRQ that has occurred is disabled lately however enabled automatically by Kernel after IRQ handler finishes. Is that correct? This also happens in delayed manner.Can anyone explain me how exactly the IRQ disabling is delayed? >From free-electrons link <http://free-electrons.com/kerneldoc/latest/DocBook/genericirq/Highlevel_IRQ…>, what I read is :- *The interrupt is kept enabled and is masked in the flow handler when an interrupt event happens*. This prevents losing edge interrupts on hardware which does not store an edge interrupt event while the interrupt is disabled at the hardware level. Can anyone please explain the bold line here? Regards, Priyaranjan

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Re: Porting to an S3C2416 failed with no console message
by Woody Wu Feb. 24, 2016

Feb. 24, 2016

On Wednesday, February 24, 2016, nick <xerofoify(a)gmail.com> wrote: > > > On 2016-02-23 09:35 AM, Woody Wu wrote: > > Hi, > > > > I am trying to port 3.18 kernel to a S3C2416. Years ago, a guy helped me > > ported a 3.1.0 kernel to the same board, and the guy left and the kernel > > got too old. The guy also ported an u-boot as boot loader to load the > 3.1.0 > > kernel. I had the source code of the ported u-boot and the 3.1.0 linux. > > > > Now, my problem is that my porting of 3.18 seems not working, I did not > see > > any kernel message printed to the first SoC serial port as I expected. As > > long as I can get kernel message printed to the serial, I think I can > step > > by step finish the whole porting work eventually. But now, there is no > > message and I have no other hardware debugging tools and knowledges, I > felt > > I lost my way totally. > > > > I hope someone can give me some suggestions, clues to help me > > understand where to check and what's the possible causes. > > > Firstly my knowledge with kernel upstream porting to a non mainlined > port is not as good as some of the other people here but let's see what > I can do. > Since I found the old porting of the 3.1.0 is quit similar to SMDK2416, > > then I started my work from also the SMDK2416 board code in 3.18. > > Basically, I defined the machine-code to match that passed from u-boot, > and > > copied the MACHINE-START definition section with removing of some > > not-immediately-needed stuff such as USB, NAND and HMSUI etc. I also > > enabled the S3C2410 serial driver and enabled the serial console > supporting > > for the Samsung SoC. Of course, I had the kernel parameter of > > "console=ttySAC0", ttySAC0 is the Linux device name of the first UART > port > > in the SoC. These are basically what I had done and I guess the SoC > serial > > part between my board and SMDK2416 should be very similar and the kernel > > should at least be able to print it's first message then I should have > > chance to fix other differences. But there is no kernel message at all > as I > > mentioned above. > > Can you either send me the patch series that the other developer used to > port > your port to 3.1.0 or I would recommend stating on kernel 3.1.0 as it's > still > a longterm kernel unless you have reason to upgrade. If you do I would > recommend > you either get something with experience or yourself to try and upstream > the > differences between your board and the mainline so others will not have to > do > the same work as you unless your company will not allow you to do this. > > What should I check for the problem usually? Is there a checking list to > go > > through? I hope you experts can give me some clues. Thanks in advance! > > To make a patch, I have to have the original 3.1.0, but I was confused about how the kernel.org organized, I just cannot find how to get a 3.1.0 tarball or git repository. Can you please give me a hint? BTW, I also dont really understand what the 'mainline' mens. If I download a latest 3.18.27.tar.xz, is it a mainline? > Their are two things you can do here either try and enable early_printk as > this > seems to be happening before the serial console is able to print the first > kernel > message. The second is trying to enable kgdb on the board and use another > computer > over the serial port to do this sort of debugging. > Hope this gets you started, > Nick Firstly, I will try early_printk soon. Before that, can your tell me what are differences betweenthe following printing technologies: 1, early_printk 2, early_print, 3, putc used in arch/arm/compressed/misc.c. Secondly, I have a question about kgdb. You see the situation is that my serial port had been initialized by the u-boot, but not yet touched by the kernel since the kernel is not yet run and waiting for debugging, and now I am jusr sitting in the u-boot command prompt and has an uImage kernel image file loaded in a region of SDRAM, do you think that these all above are enough or possible to the kgdb debugging? Many thanks! > Best Regards, > > woody > > > > > > > > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies(a)kernelnewbies.org <javascript:;> > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > -- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer woody public key at http://subkeys.pgp.net:11371 (narkewoody(a)gmail.com)

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Partial (?) kernel crash dump ?
by Rolland Santimano Feb. 24, 2016

Feb. 24, 2016

I'm trying to save a crashdump on a DellFC630 with 128G of RAM, running Ubuntu 14.10, kernel 3.16.0-23-generic; used to host a bunch of KVM-style VMs. Since saving the full dump is taking forever & a day, I'm looking to save a partial dump -- maybe a few addr space regions only from the kernel VAS. Is this even possible ? Any other options ? Or am I missing something here ? -- Rolland

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Kernel Panic in FIPS mode
by Tapas Sarangi Feb. 23, 2016

Feb. 23, 2016

I am recompiling 3.18.27 on a platform derived from el6. FIPS mode is enabled by checking the following configs: CONFIG_CRYPTO_FIPS=y CONFIG_CRYPTO_TEST=y Following RH docs, initramfs was regenerated using dracut-fips (el6). I also generated hmac signed vmlinuz during the compilation. During boot, kernel panics with the following trace: kernel line has the arguments, 'fips=1 boot=/dev/sda1'. "end Kernel Panic - not syncing: Module crc32c_intel signature verification failed in FIPS mode" Some additional info: It seems under fips mode, initrd runs, './sbin/fips.sh' which then runs 'modprobe tcrypt'. I tried running modprobe tcrypt without the fips mode on the same kernel, but it fails with this message. FATAL: Error inserting tcrypt (/lib/modules/3.18.27-1.timbuktu/kernel/crypto/tcrypt.ko.gz): Unknown symbol in module, or unknown parameter (see dmesg) Looking at dmesg: [ 31.248054] sha256_ssse3: Using AVX optimized SHA-256 implementation [ 31.308174] sha512_ssse3: Using AVX optimized SHA-512 implementation [ 31.407674] alg: No test for crc32 (crc32-pclmul) [ 31.408410] alg: No test for crc32 (crc32-table) [ 31.409086] alg: hash: Failed to load transform for hmac(crc32): -2 [ 31.413155] alg: No test for fips(ansi_cprng) (fips_ansi_cprng) [ 31.440281] tcrypt: one or more tests failed! Now, one of these messages, [ 31.409086] alg: hash: Failed to load transform for hmac(crc32): -2 comes, most likely from : linux-3.18.27/crypto/tcrypt.c (L1498) case 110: ret += tcrypt_test("hmac(crc32)"); break; and also from linux-3.18.27/crypto/testmgr.c .alg = "hmac(crc32)", .test = alg_test_hash, .suite = { .hash = { .vecs = bfin_crc_tv_template, .count = BFIN_CRC_TEST_VECTORS } } Any suggestion on how to solve this problem would be appreciated. Please let me know if I can provide more info. I am ready to help on that.

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Test e-mail, please ignore...
by Valdis Kletnieks Feb. 23, 2016

Feb. 23, 2016

For some reason, I'm not seeing posts I send to the list. (Has somebody changed the list config, or is there something more subtle going on?)

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Fwd: Re: Project Idea..
by SUNITA Feb. 23, 2016

Feb. 23, 2016

---------- Forwarded message ---------- From: "SUNITA" <sunitad100(a)gmail.com> Date: 23 Feb 2016 17:23 Subject: Re: Project Idea.. To: "Mulyadi Santosa" <mulyadi.santosa(a)gmail.com> Cc: Dear Mulyadi, Thank you for your reply. I m proceeding with the modification in CFS. Hope this will be useful research. Regards, Sunita On 2/22/16, Mulyadi Santosa <mulyadi.santosa(a)gmail.com> wrote: > On Mon, Feb 22, 2016 at 12:24 PM, SUNITA <sunitad100(a)gmail.com> wrote: > >> Respected Sir/Madam, >> I am trying to study the effect of Scheduler Policies on Energy >> Consumption of Portable Device. >> >> This will be achieved by modifying the current Completely Fair >> Scheduler by changing the range of nice values from 40 to 100 and >> adding a new scheduing policy. >> CFS uses SCHED_RR, SCHED_FCFS, SCHED_OTHER, SCHED_BATCH Policy for >> scheduling any process. The idea is to insert a new scheduling policy >> by modifying the header files. >> >> Can this be a good topic to carry out research.I welcome any other >> idea related Linux Kernel CFS. >> >> Regards, >> SUNIITA >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > > Hi Suniita > > Sounds challenging. > > It might be good topic. Just make sure you understand how to measure power > consumption and prepare various scenario of load simulation to mimic real > power consumption pattern. > > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > > This email has been sent from a virus-free computer protected by Avast. > www.avast.com <https://www.avast.com/sig-email> > <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2> >

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Porting to an S3C2416 failed with no console message
by Woody Wu Feb. 23, 2016

Feb. 23, 2016

Hi, I am trying to port 3.18 kernel to a S3C2416. Years ago, a guy helped me ported a 3.1.0 kernel to the same board, and the guy left and the kernel got too old. The guy also ported an u-boot as boot loader to load the 3.1.0 kernel. I had the source code of the ported u-boot and the 3.1.0 linux. Now, my problem is that my porting of 3.18 seems not working, I did not see any kernel message printed to the first SoC serial port as I expected. As long as I can get kernel message printed to the serial, I think I can step by step finish the whole porting work eventually. But now, there is no message and I have no other hardware debugging tools and knowledges, I felt I lost my way totally. I hope someone can give me some suggestions, clues to help me understand where to check and what's the possible causes. Since I found the old porting of the 3.1.0 is quit similar to SMDK2416, then I started my work from also the SMDK2416 board code in 3.18. Basically, I defined the machine-code to match that passed from u-boot, and copied the MACHINE-START definition section with removing of some not-immediately-needed stuff such as USB, NAND and HMSUI etc. I also enabled the S3C2410 serial driver and enabled the serial console supporting for the Samsung SoC. Of course, I had the kernel parameter of "console=ttySAC0", ttySAC0 is the Linux device name of the first UART port in the SoC. These are basically what I had done and I guess the SoC serial part between my board and SMDK2416 should be very similar and the kernel should at least be able to print it's first message then I should have chance to fix other differences. But there is no kernel message at all as I mentioned above. What should I check for the problem usually? Is there a checking list to go through? I hope you experts can give me some clues. Thanks in advance! Best Regards, woody -- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer woody public key at http://subkeys.pgp.net:11371 (narkewoody(a)gmail.com)

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Books Regarding Linux Kernel
by Anil Nair Feb. 22, 2016

Feb. 22, 2016

Hi, Can anyone suggest any good book for understanding the Linux Kernel? Are these books enough for understanding workings of Linux Kernel? 1.Linux Kernel in a Nutshell 2.Linux Device Drivers, Third Edition 3.Linux Kernel Development (3rd Edition) -- -- Regards, Anil Nair

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Re: Kernelnewbies Digest, Vol 63, Issue 37
by Sriraam VG Feb. 22, 2016

Feb. 22, 2016

Can someone suggest me a book on how to start contributing for linux kernel or any tutorial videos or any leads ? Thanks and regards Sriraam VG On Mon, Feb 22, 2016 at 11:32 AM, <kernelnewbies-request(a)kernelnewbies.org> wrote: > Send Kernelnewbies mailing list submissions to > kernelnewbies(a)kernelnewbies.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > or, via email, send a message with subject or body 'help' to > kernelnewbies-request(a)kernelnewbies.org > > You can reach the person managing the list at > kernelnewbies-owner(a)kernelnewbies.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Kernelnewbies digest..." > > > Today's Topics: > > 1. Re:Re: Why exist coding style issue in mm_types.h (YU Bo) > 2. Re: Project Idea.. (Mulyadi Santosa) > 3. Books Regarding Linux Kernel (Anil Nair) > 4. Re: Books Regarding Linux Kernel (Shiva Shankar) > 5. Re: Books Regarding Linux Kernel (Kenneth Adam Miller) > 6. Re: Books Regarding Linux Kernel (sanjeev sharma) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 22 Feb 2016 13:05:29 +0800 (CST) > From: "YU Bo" <yuzibode(a)126.com> > Subject: Re:Re: Why exist coding style issue in mm_types.h > To: "Greg KH" <greg(a)kroah.com> > Cc: "kernelnewbies(a)kernelnewbies.org" > <kernelnewbies(a)kernelnewbies.org> > Message-ID: <5dfbf723.561d.153075e3acb.Coremail.yuzibode(a)126.com> > Content-Type: text/plain; charset="gbk" > > Hi, > At 2016-02-22 02:27:39, "Greg KH" <greg(a)kroah.com> wrote: >>On Mon, Feb 22, 2016 at 12:29:54AM +0800, YU Bo wrote: >>> Hi, >>> When read the source code of mm_types.h, i encounter _coding style_ code >>> ,such like: >>> http://lxr.free-electrons.com/source/include/linux/mm_types.h#L346 in comments. >>> Why not try to fix it? Because it is trival? >>> Actually, checkpatch.pl reports many errors and warnnings for it. >>> Only can i fix the coding style issue in staging? >> >>Yes, stick to drivers/staging/* only for coding style fixes please. > >> > Thanks a lot! >

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Why exist coding style issue in mm_types.h
by YU Bo Feb. 22, 2016

Feb. 22, 2016

Hi, When read the source code of mm_types.h, i encounter _coding style_ code ,such like: http://lxr.free-electrons.com/source/include/linux/mm_types.h#L346 in comments. Why not try to fix it? Because it is trival? Actually, checkpatch.pl reports many errors and warnnings for it. Only can i fix the coding style issue in staging? Sorry for the noisy. -- Best Regards

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