January 2015 - kernelnewbies@kernelnewbies.org

why i can't find suspend to disk(hibernation) funciont in kernel mainline statble release! Is it supported ?
by sizel Jan. 29, 2015

Jan. 29, 2015

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Use of SCHED_SOFTIRQ
by Sreejith M M Jan. 29, 2015

Jan. 29, 2015

Hi, I was reading LKD by Robert Love. I got the following idea from the book. Correct me if I am worng I was checking through source code and I found that on every timer interrupt, through sched/fair.c we are raising the SCHED_SOFTIRQ(). I was checking the relation between SCHED_SOFTIRQ and actual __schedule() function. My assumption: schedule() function is the function which selects the processes which are ready to run in run queue. schedule() function is called in every timer tick. What I was thinking is that schedule() will be called as part of handling SCHED_SOFTIRQ() . But in source code, SCHED_SOFTIRQ is handled through run_rebalance_domain() function (sched/fair.c) . I am unable to trace __schedule() from this function. Am I missing anything or my assumptions are wrong? -- Regards, Sreejith

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New member
by Satwantjit Kaur Jan. 27, 2015

Jan. 27, 2015

Hi, I am a final year B.Tech (CSE) student from NIT Jalandhar. I like programming and I know C and C++ programming languages. I have worked on IPC and socket programming in C/C++. I wish to take up a project in Linux Kernel development and contribute to it. Can somebody guide me further? -- Satwantjit Kaur

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Kernel 2.6.32.60 64bit Crash/Hung
by Giridhara RP (grp) Jan. 27, 2015

Jan. 27, 2015

Hi, I am facing crash/hang with 2.6.32.60 Kernel (64bit). My maxcpus (CONFIG_NR_CPUS) count is 64 and below is the call trace. I see log saying "BUG: spinlock lockup on CPU#74". Is it a known bug? If its fixed let me know the patch. Any pointers really appreciated. Please note, if I change maxcpus=8 kernel boots successfully. Thanks Giri [Jan 26 06:41:35.439] [ 67.606000] Non-volatile memory driver v1.3^M [ 67.616000] Linux agpgart interface v0.103^M [ 67.637000] [drm] Initialized drm 1.1.0 20060810^M [ 67.652000] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled^M [ 68.092000] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A^M [Jan 26 06:41:36.679] [ 68.846000] serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A^M [ 68.910000] 00:03: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A^M [Jan 26 06:41:37.149] [ 69.316000] brd: module loaded^M [Jan 26 06:41:41.015] [ 73.183000] loop: module loaded^M [ 73.191000] lkdtm : Invalid command^M [ 73.200000] kgdb: Registered I/O driver kgdbts.^M [Jan 26 06:42:03.435] [ 73.552000] BUG: spinlock lockup on CPU#74, swapper/1, ffff880c9c1d2ac0^M <======= [ 73.552000] Pid: 1, comm: swapper Not tainted 2.6.32.60 #2^M [ 73.552000] Call Trace:^M [ 73.552000] <IRQ> [<ffffffff81196df0>] _raw_spin_lock+0x103/0x12b^M [ 73.552000] [<ffffffff81459c97>] _spin_lock+0x4f/0x62^M [ 73.552000] [<ffffffff8103c1a3>] ? scheduler_tick+0x49/0x166^M [ 73.552000] [<ffffffff8103c1a3>] scheduler_tick+0x49/0x166^M [ 73.552000] [<ffffffff8104e6de>] update_process_times+0x42/0x52^M [ 73.552000] [<ffffffff81061ef1>] tick_periodic+0x63/0x65^M [ 73.552000] [<ffffffff81061f11>] tick_handle_periodic+0x1e/0x6b^M [ 73.552000] [<ffffffff8101eb91>] smp_apic_timer_interrupt+0x84/0x97^M [ 73.552000] [<ffffffff8100c773>] apic_timer_interrupt+0x13/0x20^M [ 73.552000] <EOI> [<ffffffff8126a8a5>] ? kgdbts_break_test+0x1/0x22^M [ 73.552000] [<ffffffff8126a8a4>] ? kgdbts_break_test+0x0/0x22^M [ 73.552000] [<ffffffff8126b7d4>] ? configure_kgdbts+0x1ef/0x4bb^M [ 73.552000] [<ffffffff81177ade>] ? blk_register_region+0x28/0x2a^M [ 73.552000] [<ffffffff81b50f4c>] ? init_kgdbts+0x0/0x16^M [ 73.552000] [<ffffffff81b50f60>] ? init_kgdbts+0x14/0x16^M [ 73.552000] [<ffffffff8100905d>] ? do_one_initcall+0x57/0x157^M [ 73.552000] [<ffffffff81b24d88>] ? kernel_init+0x1f0/0x241^M [ 73.552000] [<ffffffff8100cc7a>] ? child_rip+0xa/0x20^M [ 73.552000] [<ffffffff8100c63c>] ? restore_args+0x0/0x30^M [ 73.552000] [<ffffffff81b24b98>] ? kernel_init+0x0/0x241^M [ 73.552000] [<ffffffff8100cc70>] ? child_rip+0x0/0x20^M [ 73.552000] sending NMI to all CPUs:^M [ 73.552000] NMI backtrace for cpu 74^M [ 73.552000] CPU 74:^M [ 73.552000] Modules linked in:^M [ 73.552000] Pid: 1, comm: swapper Not tainted 2.6.32.60 #2 UCSB-B420-M3^M [ 73.552000] RIP: 0010:[<ffffffff81187fa0>] [<ffffffff81187fa0>] delay_loop+0x20/0x2a^M [ 73.552000] RSP: 0018:ffff880c9c003da8 EFLAGS: 00000002^M [ 73.552000] RAX: 000000000001d185 RBX: 0000000000000000 RCX: 0000000000000030^M [ 73.552000] RDX: 000000000001d19a RSI: 0000000000000010 RDI: 000000000001d19b^M [ 73.552000] RBP: ffff880c9c003da8 R08: 000000000000000b R09: ffffffff81947ad0^M [ 73.552000] R10: 000000000000b4a0 R11: ffffffff81878da0 R12: 0000000000001000^M [ 73.552000] R13: 0000000000000092 R14: 0000000000000002 R15: ffffffff81947ac0^M [ 73.552000] FS: 0000000000000000(0000) GS:ffff880c9c000000(0000) knlGS:0000000000000000^M [ 73.552000] CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b^M [ 73.552000] CR2: 0000000000000000 CR3: 0000000001001000 CR4: 00000000000406e0^M [ 73.552000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 000000000000 [Jan 26 06:42:04.041] 0000^M [ 73.552000] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400^M [ 73.552000] Call Trace:^M [ 73.552000] <#DB[1]> <<EOE>> Pid: 1, comm: swapper Not tainted 2.6.32.60 #2^M [ 73.552000] Call Trace:^M [ 73.552000] <NMI> [<ffffffff8145b99d>] nmi_watchdog_tick+0x111/0x24d^M [ 73.552000] [<ffffffff8145aee1>] do_nmi+0xbd/0x269^M [ 73.552000] [<ffffffff8145ab1a>] nmi+0x1a/0x2c^M [ 73.552000] [<ffffffff81187fa0>] ? delay_loop+0x20/0x2a^M [ 73.552000] <<EOE>> <IRQ> [<ffffffff81188001>] __delay+0xa/0xc^M [ 73.552000] [<ffffffff8118803f>] __const_udelay+0x3c/0x3e^M [ 73.552000] [<ffffffff8101e898>] native_safe_apic_wait_icr_idle+0x31/0x44^M [ 73.552000] [<ffffffff8101f479>] default_send_IPI_mask_sequence_phys+0x49/0x110^M [ 73.552000] [<ffffffff810225f4>] physflat_send_IPI_mask+0x9/0xb^M [ 73.552000] [<ffffffff8102262b>] physflat_send_IPI_all+0x14/0x16^M [ 73.552000] [<ffffffff8101f8e6>] arch_trigger_all_cpu_backtrace+0x4e/0x7c^M [ 73.552000] [<ffffffff81196df5>] _raw_spin_lock+0x108/0x12b^M [ 73.552000] [<ffffffff81459c97>] _spin_lock+0x4f/0x62^M [ 73.552000] [<ffffffff8103c1a3>] ? scheduler_tick+0x49/0x166^M [ 73.552000] [<ffffffff8103c1a3>] scheduler_tick+0x49/0x166^M [ 73.552000] [<ffffffff8104e6de>] update_process_times+0x42/0x52^M [ 73.552000] [<ffffffff81061ef1>] tick_periodic+0x63/0x65^M [ 73.552000] [<ffffffff81061f11>] tick_handle_periodic+0x1e/0x6b^M [ 73.552000] [<ffffffff8101eb91>] smp_apic_timer_interrupt+0x84/0x97^M [ 73.552000] [<ffffffff8100c773>] apic_timer_interrupt+0x13/0x20^M [ 73.552000] <EOI> [<ffffffff8126a8a5>] ? kgdbts_break_test+0x1/0x22^M [ 73.552000] [<ffffffff8126a8a4>] ? kgdbts_break_test+0x0/0x22^M [ 73.552000] [<ffffffff8126b7d4>] ? configure_kgdbts+0x1ef/0x4bb^M [ 73.552000] [<ffffffff81177ade>] ? blk_register_region+0x28/0x2a^M [ 73.552000] [<ffffffff81b50f4c>] ? init_kgdbts+0x0/0x16^M [ 73.552000] [<ffffffff81b50f60>] ? init_kgdbts+0x14/0x16^M [ 73.552000] [<ffffffff8100905d>] ? do_one_initcall+0x57/0x157^M [ 73.552000] [<ffffffff81b24d88>] ? kernel_init+0x1f0/0x241^M [ 73.552000] [<ffffffff8100cc7a>] ? child_rip+0xa/0x20^M [ 73.552000] [<ffffffff8100c63c>] ? restore_args+0x0/0x30^M [ 73.552000] [<ffffffff81b24b98>] ? kernel_init+0x0/0x241^M [ 73.552000] [<ffffffff8100cc70>] ? child_rip+0x0/0x20^M

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(no subject)
by Grzegorz Dwornicki Jan. 27, 2015

Jan. 27, 2015

Keepalive question Hello I am bothered with very simple situaction. Lets say we have a TCP connection: S1 <----> S2 Lets assume that this connection is using blocking sockets. and that both hosts: s1 and s2 are using SO_KEEPALIVE. If they both are not using this connection then the kernel? is sending packets with no data to keep connection alive. I have marked "the kernel?" because I am not sure who does this. I think its the kernel but I am not sure. What would happen if only one of them would use keepalive? Could that empty packet break the loop inside of sk_busy_loop function and return empty data to the application layer? Or would that while loop body just re-run? Hehe is the code (the while loop starts on 128 line) http://lxr.oss.org.cn/source/include/net/busy_poll.h?a=arm#L95

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Fwd: New member
by srinivas bakki Jan. 27, 2015

Jan. 27, 2015

Valdis, You got to be polite with people.Not everybody is as smart as you, but they would like to contribute. Just keep in in mind that there's no future for linux without such people. You cannot keep bullying everybody like this. On Mon, Jan 26, 2015 at 12:46 AM, Surendra Patil <surendra.tux(a)gmail.com> wrote: > Hi Kaur, > > I would recommend you take a look at this videos by Greg - > http://www.youtube.com/watch?v=LLBrBBImJt4. > He has explained how to get started to contribute Linux Kernel. > > Good Luck !!! > > > On Sun, Jan 25, 2015 at 10:31 AM, <Valdis.Kletnieks(a)vt.edu> wrote: > >> On Sun, 25 Jan 2015 10:07:44 -0800, Satwantjit Kaur said: >> > I am a final year B.Tech (CSE) student from NIT Jalandhar. I like >> > programming and I know C and C++ programming languages. I have worked >> > on IPC and socket programming in C/C++. I wish to take up a project in >> > Linux Kernel development and contribute to it. Can somebody guide me >> > further? >> >> I'll be blunt. Unless you *already* have an interest or desire in a >> particular >> part of the kernel (for instance, filesystems, or networking, or memory >> management, etc), you probably aren't a good fit for actually >> contributing to >> the Linux kernel. You might be able to hack up some code that will >> satisfy a >> professor for a project, but actual contributions are usually held to a >> higher >> standard. >> >> Consider the difference between "I'd like to write a book, but have no >> idea >> what to write about, can somebody suggest whether to write fantasy, or a >> romance, or non-fiction about sports, or something", and "I'm thinking >> about a >> story about the adventures of a Roman centurion fighting the Gauls, but >> need >> help making it historically accurate". >> >> Pretty much everybody will agree that the first book is doomed, because >> the author obviously isn't connected that much to their project. The >> second? >> That has a *much* higher chance of producing a good story, simply because >> the author has a vision for the project that they can stick to. >> >> And that affects mentoring - nobody who knows anything about writing >> fantasy >> novels will be interested in helping somebody who hasn't even decided if >> they want to write about fantasy or scuba diving. Somebody who knows they >> want to write about a Roman centurion fighting the Gauls? At that point, >> it's worth the 5 minutes for a Roman history expert to give suggestions >> and references to the way things were then.... >> >> And the Linux kernel is the same way. >> >> Now, if you have a professor that's *insisting* on a Linux kernel project, >> that's an entirely different problem. ;) >> >> >> >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> >> > > > -- > ------------------------------ > Best, > Surendra Patil > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >

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Re: Ticketing spinlocks - How to get to the owner who locked the spinlock?
by Arun KS Jan. 27, 2015

Jan. 27, 2015

Hi Manty, On Tue, Jan 27, 2015 at 11:52 AM, manty kuma <mantykuma(a)gmail.com> wrote: > Dear Arun, > > typedef struct raw_spinlock { > arch_spinlock_t raw_lock; > #ifdef CONFIG_GENERIC_LOCKBREAK > unsigned int break_lock; > #endif > #ifdef CONFIG_DEBUG_SPINLOCK > unsigned int magic, owner_cpu; > void *owner; > #endif > #ifdef CONFIG_DEBUG_LOCK_ALLOC > struct lockdep_map dep_map; > #endif > } raw_spinlock_t; > > > Unfortunately, CONFIG_DEBUG_SPINLOCK is disabled on my sw. So i do not have > this information. :( > > Any other way? What is the output from your runq command? Thanks, Arun > > On Tue, Jan 27, 2015 at 3:12 PM, Arun KS <getarunks(a)gmail.com> wrote: >> >> Hello Manty, >> >> On Tue, Jan 27, 2015 at 11:27 AM, manty kuma <mantykuma(a)gmail.com> wrote: >> > >> > Hi All, >> > >> > Currently I am looking into an issue which is holding the printk >> > lock(logbuf_lock) >> > >> > logbuf_lock = { >> > raw_lock = { >> > owner = 0, >> > next = 4 >> > } >> > } >> > >> > I read about ticketing spinlocks to understand the above output. I >> > understood that 4 cpu's are waiting for the lock while someone already has >> > it. >> > >> > I would like to know who has it? Is there a way I can know which process >> > is acquiring a given spinlock? Is the information not stored in it? >> > >> > I am using crash tool to analyse the dump >> >> >> crash> raw_spinlock_t >> typedef struct raw_spinlock { >> arch_spinlock_t raw_lock; >> unsigned int magic; >> unsigned int owner_cpu; >> void *owner; >> } raw_spinlock_t; >> SIZE: 16 >> >> The owner field points to task holding the lock, if locked. >> >> Here is what i have in one of my dumps, >> crash> logbuf_lock >> logbuf_lock = $6 = { >> raw_lock = { >> { >> slock = 464001960, >> tickets = { >> owner = 7080, >> next = 7080 >> } >> } >> }, >> magic = 3735899821, >> owner_cpu = 4294967295, >> owner = 0xffffffff >> } >> >> since lock is not acquired, it shows 0xFFFFFFFF. >> Otherwise point to a task_struct *. >> >> thanks, >> Arun >> >> > >> > >> > Regards, >> > Manty >> > >> > _______________________________________________ >> > Kernelnewbies mailing list >> > Kernelnewbies(a)kernelnewbies.org >> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > > >

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Ticketing spinlocks - How to get to the owner who locked the spinlock?
by manty kuma Jan. 27, 2015

Jan. 27, 2015

Hi All, Currently I am looking into an issue which is holding the printk lock(logbuf_lock) logbuf_lock = { raw_lock = { owner = 0, next = 4 } } I read about ticketing spinlocks to understand the above output. I understood that 4 cpu's are waiting for the lock while someone already has it. I would like to know who has it? Is there a way I can know which process is acquiring a given spinlock? Is the information not stored in it? I am using crash tool to analyse the dump Regards, Manty

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Block Device Driver Tutorial
by Gunjan Mehta Jan. 27, 2015

Jan. 27, 2015

Hi All, I am looking for some good tutorials for block device driver. It would be great someone knows best training center in India(Bangalore,Pune,Mumbai) Regards

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RE: Kernel 2.6.32.60 64bit Crash/Hung
by Giridhara RP (grp) Jan. 27, 2015

Jan. 27, 2015

Hello, Please note my CPU is this. Intel(R) Xeon(R) CPU E5-4650 v2 @ 2.40GHz stepping 04 From: Giridhara RP (grp) Sent: Tuesday, January 27, 2015 5:37 AM To: kernelnewbies(a)kernelnewbies.org Subject: Kernel 2.6.32.60 64bit Crash/Hung Hi, I am facing crash/hang with 2.6.32.60 Kernel (64bit). My maxcpus (CONFIG_NR_CPUS) count is 64 and below is the call trace. I see log saying "BUG: spinlock lockup on CPU#74". Is it a known bug? If its fixed let me know the patch. Any pointers really appreciated. Please note, if I change maxcpus=8 kernel boots successfully. Thanks Giri

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