October 2011 - kernelnewbies@kernelnewbies.org

dma_alloc_coherent
by bob jonny Oct. 13, 2011

Oct. 13, 2011

In dma_alloc_coherent(), where is it allocating memory from, and how does it know that that memory is cache coherent? Does every device have it's cache coherent memory? I got lost at function pointer struct dma_map_ops ops, is there an easy way to figure out what ops->alloc_coherent() points to?

2 1

System scheduling, signals, etc.
by dpc＠ucore.info Oct. 12, 2011

Oct. 12, 2011

Hi, I'm working on some particularly complex kernel hacking thing and I thought that I could use some input from more experienced guys and thought that LKML might not be a best place to ask this, while Kernelnewbies seems more appropriate, even thought I'm not entirely newbie. I'm dealing with a problem that my heavily modified system "hangs" while the vanilla does not. My version works fine, but at some point of booting process it stops. When I'm debugging the issue I can clearly see that scheduler is switching between swapper and kworker processes only, while other processes are sleeping: (gdb) ps 0xC09BFF10 0 Running - - (none) swapper 0xC786F280 1 Sleep(In.) - - (none) init 0xC786E960 2 Sleep(In.) - - (none) kthreadd 0xC786E040 3 Sleep(In.) - - (none) ksoftirqd/0 0xC78792A0 4 Running - - (none) kworker/0:0 0xC7878980 5 Sleep(In.) - - (none) kworker/u:0 0xC7878060 6 Sleep(In.) - - (none) cpuset 0xC78892C0 7 Sleep(In.) - - (none) khelper 0xC78889A0 8 Sleep(In.) - - (none) kworker/u:1 0xC7888080 277 Sleep(In.) - - (none) sync_supers 0xC789B2E0 279 Sleep(In.) - - (none) bdi-default 0xC78C1320 281 Sleep(In.) - - (none) kblockd 0xC78B1300 292 Sleep(In.) - - (none) ata_sff 0xC78C00E0 304 Sleep(Un.) - - (none) khubd 0xC78F1340 327 Sleep(In.) - - (none) kworker/0:1 0xC78F0A20 328 Sleep(In.) - - (none) cfg80211 0xC78F0100 411 Sleep(In.) - - (none) rpciod 0xC789A9C0 419 Sleep(In.) - - (none) khungtaskd 0xC78C0A00 420 Sleep(Un.) - - (none) kswapd0 0xC7927360 421 Sleep(In.) - - (none) fsnotify_mark 0xC78B00C0 422 Sleep(In.) - - (none) nfsiod 0xC7926A40 424 Sleep(In.) - - (none) crypto 0xC7A6CA80 523 Sleep(In.) - - (none) zd1211rw 0xC7926120 532 Sleep(In.) - - (none) libertastf 0xC7A64140 566 Sleep(In.) - - (none) kworker/0:2 0xC7A65380 573 Sleep(In.) - - (none) kpsmoused 0xC7A6D3A0 592 Sleep(In.) - - (none) kworker/u:2 0xC7A6C160 606 Sleep(In.) - - (none) mmcqd/0 0xC78B09E0 644 Sleep(In.) - - (none) jbd2/mmcblk0p2- 0xC7A9C1A0 645 Sleep(In.) - - (none) ext4-dio-unwrit 0xC7A64A60 647 Sleep(In.) - - (none) plymouthd 0xC789A0A0 649 Sleep(Un.) - - (none) plymouthd 0xC7A9D3E0 651 Sleep(Un.) - - (none) sh This is the output of macro that I'm using. (In.) == Interruptable; (Un.) == Uninterraptable The problem is: I don't entirely understand all the details about scheduling/task primitives and the problem can sit just anywhere: my changes touch the bare bones of exception handling etc. I wish to know: - what data structures and fields should I check to see if there are any pending signals - what all the stuff in scheduling data? - how would you approach such problem while being able to run two versions (modified and vanilla) side by side - what are critical functions in kernel code that are dealing with waking and putting processes into sleep; I wish to break debbugger on them or put some printk's here and there and look for some pattern Can you throw some ideas or links/books to read? Much appreciated. Best Regards, -- Dawid Ciężarkiewicz

1 0

kernel version incorporating a particular feature
by amit mehta Oct. 12, 2011

Oct. 12, 2011

How do i find the linux kernel version from which a certain feature was first incorporated. For example , How do i find the first kernel version which had support for GRO (generic receive offload) ? Thanks, Amit

4 6

File change notification along with user
by V.Ravikumar Oct. 12, 2011

Oct. 12, 2011

Hi all, Is it possible to write a module/driver which notifies file/directory change asynchronously along with user name(or with uid) who modified it. inotify will do change notification but it will not provide uid who modified/created the file. audit and inotify combination can work, but I'm looking for a better option than this. Please help me. Thanks, Ravi

3 7

Linux kernel networking stack
by Abu Rasheda Oct. 12, 2011

Oct. 12, 2011

I want to embark on journey of learning Linux networking stack. I want suggestions, what is best way to do this. Any book recommendation, any documentation which might exist. Thanks.

6 5

Writing a USB driver for a non working device
by madav maddy Oct. 12, 2011

Oct. 12, 2011

Hi, I am newbie. For the better understanding of the USB, i have decided write a USB driver for the device for which it works in windows but not in linux. So i have picked the Logitech USB headset. The background i have is ,i have studied the ldd usb drivers and written few dummy USB driver. Before i start implementing, i made some basic study - on connecting the device to my Ubuntu desktop, lsusb shows * Bus 002 Device 065: ID 046d:0a01 Logitech, Inc. USB Headset* on issuing dmesg. [550289.589037] usb 2-1.6: new full speed USB device using ehci_hcd and address 66 - so i believe there should be some driver already existing, is my understanding right? - if not, where can i start for implementing a new driver of my own? I think i need start doing some reverse engineering on windows using some usb logging tool, for the understanding of working of the device Thanks, Madav Raman

2 1

Re Likely and Unlikely Macro
by Asutosh Das Oct. 12, 2011

Oct. 12, 2011

Hi In lxr, I saw the likely and unlikely macro defined as (compiler.h) # define likely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1)) 116# endif 117# ifndef unlikely 118# define unlikely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0)) 119# endif 120 ..... some other defines #else 146# define likely(x) __builtin_expect(!!(x), 1) 147# define unlikely(x) __builtin_expect(!!(x), 0) 148#endif I cannot understand the intention behind !!(x). Please can you let me know why !!(x) is required here. TIA -- ~/asd

4 4

interpret the result of perf stat
by Zheng Da Oct. 12, 2011

Oct. 12, 2011

Hello, I start to use perf to profile my program, but I'm not quite sure if I understand some events. First, perf can profile bus cycles. Is it the bus cycles of FSB? Second, what is task clock? It seems to me that task clock is the ticks used by a process. It should include the ticks used in the kernel mode and the user space mode, as long as it is used in the context of the process. I suppose it doesn't count the cycles used by the interrupts such as page faults and softirq, even though the irqs are caused by the process. Is it correct? Thanks, Da

4 9

Finding out when a process has died
by MK Oct. 11, 2011

Oct. 11, 2011

Hi, I want to write a process (hopefully userspace) which will "watch" other processes and do something when a process dies. What is a good way to do this? A simple solution would be to have a stream/tcp connection between the watcher and other processes and when the connection is broken, you know the other side has died. Is there a better way to do this possibly involving a kernel mod? Thanks!!

3 2

kernel 5.5 kernel and tg3 driver
by sri Oct. 11, 2011

Oct. 11, 2011

Hello Experts, I was using click-1.6.0 on centos 5.3 kernel and recently* ported that to centos5.5 kernel.*. After porting, am getting the (*low stack detected by irq handler) and the *following errors on the console frequently and causing the system unresponsive totally. Even after reboot, this issue is re-occurring some time after every 3 days. System info: kernel: centos 5.5 (2.6.194-el5) kernel Modules using: click router NIC driver: tg3 (broadcom) Note: The above setup was working successfully for years earlier. I suspect tg3 driver is doing something here but not sure of how to confirm this. Am looking for pointers to start with so that I can investigate. I tried to do web search on this but not useful. Also, would like to know any ways/tools to debug using the addresses given in the stack trace. Thanks in advance. ######################## *START OF LOGS* ############################ Oct 1 14:16:56 server03 kernel: low stack detected by irq handler Oct 1 14:16:56 server03 kernel: [<c0405e9b>] do_IRQ+0x86/0xc3 Oct 1 14:16:56 server03 kernel: [<c04046e6>] common_interrupt+0x1a/0x20 Oct 1 14:16:56 server03 kernel: [<c05a5c06>] neigh_lookup+0x23/0x7f Oct 1 14:16:56 server03 kernel: [<c05d6800>] arp_bind_neighbour+0x50/0x71 Oct 1 14:16:56 server03 kernel: [<c05b7b44>] rt_intern_hash+0x372/0x480 Oct 1 14:16:56 server03 kernel: [<c05b8352>] __ip_route_output_key+0x700/ 0x79e Oct 1 14:16:56 server03 kernel: [<c05b83d4>] __ip_route_output_key+0x782/0x79e Oct 1 14:16:57 server03 kernel: [<c05b8403>] ip_route_output_flow+0x13/0x1d4 Oct 1 14:16:57 server03 kernel: [<c05b85cd>] ip_route_output_key+0x9/0xb Oct 1 14:16:57 server03 kernel: [<c05bdd5d>] ip_send_reply+0xf8/0x209 Oct 1 14:16:57 server03 kernel: [<c045f1a6>] cache_alloc_refill+0x122/0x3e4 Oct 1 14:16:57 server03 kernel: [<c05b7c2f>] rt_intern_hash+0x45d/0x480 Oct 1 14:16:57 server03 kernel: [<c05cfc56>] tcp_v4_send_reset+0x104/0x11c Oct 1 14:16:57 server03 kernel: [<c05d0879>] tcp_v4_do_rcv+0x240/0x269 Oct 1 14:16:57 server03 kernel: [<c05d28cb>] tcp_v4_rcv+0x7f7/0x848 Oct 1 14:16:57 server03 kernel: [<c05bb173>] ip_local_deliver+0x157/0x1d0 Oct 1 14:16:57 server03 kernel: [<c05baff2>] ip_rcv+0x3cb/0x3f5 Oct 1 14:16:57 server03 kernel: [<c05a141d>] __netif_receive_skb+0x3b3/0x3d5 Oct 1 14:16:57 server03 kernel: [<fb1b121e>] _ZN6ToHost4pushEiP6Packet+0xee/0x210 [click] Oct 1 14:16:57 server03 kernel: [<fb1ce85d>] _ZN12EnsureEther24pushEiP6Packet+0x1d/0x20 [click] Oct 1 14:16:57 server03 kernel: [<fb1c0895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click] Oct 1 14:16:57 server03 kernel: [<c05bb173>] ip_local_deliver+0x157/0x1d0 Oct 1 14:16:57 server03 kernel: [<c05baff2>] ip_rcv+0x3cb/0x3f5 Oct 1 14:16:57 server03 kernel: [<fb19e42d>] _ZN4IPRw7Mapping9make_pairEiRK8IPFlowIDS3_iiPS0_S4_+0xad/0xd0 [click] Oct 1 14:16:57 server03 kernel: [<fb19fcfb>] _ZN4IPRw7Pattern14create_mappingEiRK8IPFlowIDiiPNS_7MappingES5_RK7HashMapIS1_S5_E+0x1cb/0x1f0 [click] Oct 1 14:16:57 server03 kernel: [<fb218ce3>] _ZN10IPRewriter13apply_patternEPN4IPRw7PatternEiRK8IPFlowIDii+0x153/0x160 [click] Oct 1 14:16:57 server03 kernel: [<fb218d9e>] _ZN10IPRewriter4pushEiP6Packet+0xae/0x260 [click] Oct 1 14:16:57 server03 kernel: [<fb1ea535>] _ZN11MacThrottle10l2PushProcEiP6Packet+0x55/0x3b0 [click] Oct 1 14:16:57 server03 kernel: [<fb1c0895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click] Oct 1 14:16:57 server03 kernel: [<fb218ce3>] _ZN10IPRewriter13apply_patternEPN4IPRw7PatternEiRK8IPFlowIDii+0x153/0x160 [click] Oct 1 14:16:57 server03 kernel: [<fb218d9e>] _ZN10IPRewriter4pushEiP6Packet+0xae/0x260 [click] Oct 1 14:16:58 server03 kernel: [<fb1eab96>] _ZN11MacThrottle4pushEiP6Packet+0x306/0x1890 [click] Oct 1 14:16:58 server03 kernel: [<c0417f22>] enqueue_task+0x29/0x39 Oct 1 14:16:58 server03 kernel: [<c041805a>] __activate_task+0x4a/0x59 Oct 1 14:16:58 server03 kernel: [<fb1c69d8>] _ZN8BWShaper4pushEiP6Packet+0x58/0xe90 [click] Oct 1 14:16:58 server03 kernel: [<fb155806>] _ZN7Element4pushEiP6Packet+0x26/0x40 [click] Oct 1 14:16:58 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:58 server03 kernel: [<fb1ee075>] _ZN17NtlmLoginDetector4pushEiP6Packet+0x65/0x15d0 [click] Oct 1 14:16:58 server03 kernel: [<fb155806>] _ZN7Element4pushEiP6Packet+0x26/0x40 [click] Oct 1 14:16:58 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:58 server03 kernel: [<fb21f881>] _ZN15RecycledSkbPool7recycleEP7sk_buff+0x31/0xf0 [click] Oct 1 14:16:58 server03 kernel: [<fb1fbfdb>] _ZN14PerfigoDiscard4pushEiP6Packet+0x4b/0x1c0 [click] Oct 1 14:16:58 server03 kernel: [<c05bb173>] ip_local_deliver+0x157/0x1d0 Oct 1 14:16:58 server03 kernel: [<fb1d8e86>] _ZN11HashIPTable4pushEiP6Packet+0xf6/0x2d0 [click] Oct 1 14:16:58 server03 kernel: [<c05a141d>] __netif_receive_skb+0x3b3/0x3d5 Oct 1 14:16:58 server03 kernel: [<fb1c69d8>] _ZN8BWShaper4pushEiP6Packet+0x58/0xe90 [click] Oct 1 14:16:58 server03 kernel: [<fb192904>] _ZN8IPFilter4pushEiP6Packet+0x64/0xf0 [click] Oct 1 14:16:58 server03 kernel: [<fb1e4517>] _ZN12IPPortLookup4pushEiP6Packet+0x47/0x9e0 [click] Oct 1 14:16:58 server03 kernel: [<c043f334>] __do_IRQ+0x0/0x9f Oct 1 14:16:58 server03 kernel: [<c0405ecc>] do_IRQ+0xb7/0xc3 Oct 1 14:16:58 server03 kernel: [<c043f334>] __do_IRQ+0x0/0x9f Oct 1 14:16:58 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:58 server03 kernel: [<fb1cd5fc>] _ZN10DnsHandler17is_packet_allowedEPK6Packeti+0x8c/0x5e0 [click] Oct 1 14:16:59 server03 kernel: [<fb1c69d8>] _ZN8BWShaper4pushEiP6Packet+0x58/0xe90 [click] Oct 1 14:16:59 server03 kernel: [<fb1c69d8>] _ZN8BWShaper4pushEiP6Packet+0x58/0xe90 [click] Oct 1 14:16:59 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:59 server03 kernel: [<fb1cdbb8>] _ZN10DnsHandler4pushEiP6Packet+0x68/0xb00 [click] Oct 1 14:16:59 server03 kernel: [<fb1b1853>] _ZN11ARPQuerier214send_query_forERK9IPAddressitit+0x133/0x3f0 [click] Oct 1 14:16:59 server03 kernel: [<fb1b1dba>] _ZN11ARPQuerier29handle_ipEP6Packet+0x2aa/0x5f0 [click] Oct 1 14:16:59 server03 kernel: [<fb1b31bd>] _ZN11ARPQuerier24pushEiP6Packet+0xcd/0x110 [click] Oct 1 14:16:59 server03 kernel: [<fb1cdbb8>] _ZN10DnsHandler4pushEiP6Packet+0x68/0xb00 [click] Oct 1 14:16:59 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:59 server03 kernel: [<fb1cdbb8>] _ZN10DnsHandler4pushEiP6Packet+0x68/0xb00 [click] Oct 1 14:16:59 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:59 server03 kernel: [<fb1e234f>] _ZN13IPFilterGroup4pushEiP6Packet+0x19f/0xa80 [click] Oct 1 14:16:59 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:59 server03 kernel: [<fb1fb79e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click] Oct 1 14:16:59 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:59 server03 kernel: [<fb207674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click] Oct 1 14:16:59 server03 kernel: [<fb1fb79e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click] Oct 1 14:16:59 server03 kernel: [<c05a5c59>] neigh_lookup+0x76/0x7f Oct 1 14:16:59 server03 kernel: [<fb1d3492>] _ZN13HashIPLookup34pushEiP6Packet+0x112/0x1c0 [click] Oct 1 14:16:59 server03 kernel: [<fb1e66cf>] _ZN15LinearIPFilter24pushEiP6Packet+0x4f/0x3f0 [click] Oct 1 14:16:59 server03 kernel: [<fb1b80e8>] _ZN11ARPQuerier420handle_arp_retaggingEP6Packett+0x58/0x940 [click] Oct 1 14:16:59 server03 kernel: [<c05bf82d>] ip_output+0x1f0/0x227 Oct 1 14:16:59 server03 kernel: [<fb1dd289>] _ZN14HashMACLookup54pushEiP6Packet+0x249/0x890 [click] Oct 1 14:16:59 server03 kernel: [<fb1d45b7>] _ZN13HashIPLookup54pushEiP6Packet+0xc7/0x110 [click] Oct 1 14:17:00 server03 kernel: [<fb1c0895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click] Oct 1 14:17:00 server03 kernel: [<fb1fb79e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click] Oct 1 14:17:00 server03 kernel: [<fb1dcd23>] _ZN14HashMACLookup514push_extern_ipEP6Packet+0x1b3/0x4d0 [click] Oct 1 14:17:00 server03 kernel: [<fb1d762e>] _ZN12HashIPTable24pushEiP6Packet+0x18e/0x580 [click] Oct 1 14:17:00 server03 kernel: [<c05d065b>] tcp_v4_do_rcv+0x22/0x269 Oct 1 14:17:00 server03 kernel: [<c05d28cb>] tcp_v4_rcv+0x7f7/0x848 Oct 1 14:17:00 server03 kernel: [<fb1bfb12>] _ZN11ARPQuerier415handle_responseEP6Packet+0x32/0x8f0 [click] Oct 1 14:17:00 server03 kernel: [<fb21f881>] _ZN15RecycledSkbPool7recycleEP7sk_buff+0x31/0xf0 [click] Oct 1 14:17:00 server03 kernel: [<fb1fbfdb>] _ZN14PerfigoDiscard4pushEiP6Packet+0x4b/0x1c0 [click] Oct 1 14:17:00 server03 kernel: [<fb192904>] _ZN8IPFilter4pushEiP6Packet+0x64/0xf0 [click] Oct 1 14:17:00 server03 kernel: [<fb1c0895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click] Oct 1 14:17:00 server03 kernel: [<fb1fb79e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click] Oct 1 14:17:00 server03 kernel: [<fb1fb79e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click] Oct 1 14:17:00 server03 kernel: [<fb1d762e>] _ZN12HashIPTable24pushEiP6Packet+0x18e/0x580 [click] Oct 1 14:17:00 server03 kernel: [<c05d7777>] arp_rcv+0xd0/0xe1 Oct 1 14:17:00 server03 kernel: [<c05a141d>] __netif_receive_skb+0x3b3/0x3d5 Oct 1 14:17:00 server03 kernel: [<c043f334>] __do_IRQ+0x0/0x9f Oct 1 14:17:00 server03 kernel: [<c043f334>] __do_IRQ+0x0/0x9f Oct 1 14:17:00 server03 kernel: [<c0405ecc>] do_IRQ+0xb7/0xc3 Oct 1 14:17:00 server03 kernel: [<c0411f41>] smp_apic_timer_interrupt+0x32/0x45 Oct 1 14:17:00 server03 kernel: [<c040470b>] apic_timer_interrupt+0x1f/0x24 Oct 1 14:17:00 server03 kernel: [<c0405ecc>] do_IRQ+0xb7/0xc3 Oct 1 14:17:00 server03 kernel: [<c0405ecc>] do_IRQ+0xb7/0xc3 Oct 1 14:17:01 server03 kernel: [<fb1fe516>] _ZN10Classifier4pushEiP6Packet+0x76/0xe0 [click] Oct 1 14:17:01 server03 kernel: [<fb155806>] _ZN7Element4pushEiP6Packet+0x26/0x40 [click] Oct 1 14:17:01 server03 kernel: [<fb1ab2a5>] _ZN10FromDevice8run_taskEP4Task+0xa5/0x120 [click] Oct 1 14:17:01 server03 kernel: [<fb16c127>] _ZN12RouterThread6driverEv+0x177/0x290 [click] Oct 1 14:17:01 server03 kernel: [<fb21c822>] _Z11click_schedPv+0x82/0x130 [click] Oct 1 14:17:01 server03 kernel: [<fb21c7a0>] _Z11click_schedPv+0x0/0x130 [click] Oct 1 14:17:01 server03 kernel: [<c0404987>] kernel_thread_helper+0x7/0x10 Oct 1 14:17:01 server03 kernel: ======================= #######################* END OF LOGS #* ##################################################### -- -- Krishna Mohan B -- -- Krishna Mohan B

3 3