- kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

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.

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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

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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

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What is the significance of __releases & __acquires in rpm_callback() of power/runtime.c ?
by venu Oct. 11, 2011

Oct. 11, 2011

While going thro’ run time power management code in K39 power/runtime.c file, am seeing a function definition as given below. Any idea, what “__releases” & “__acquires” are doing in this function definition? static int rpm_callback(int (*cb)(struct device *), struct device *dev) __releases(&dev->power.lock) __acquires(&dev->power.lock) { int retval; …. return retval; }

2 1

userspace address to bus address
by Florian Bauer Oct. 10, 2011

Oct. 10, 2011

Hi, I'm currently writing my first kernel module, but i got stuck with address translations. I want my pcie device to access a buffer which was allocated in userspace (page aligned, currently smaller than one page to ignore scattering). I tried to translate the userspace address to a bus address in my ioctrl handler like this: void __user *data = arg; down_read(&current->mm->mmap_sem); get_user_pages(current, current->mm, (unsigned long)data, len/*1*/, 1, 0, &pages, NULL); up_read(&current->mm->mmap_sem); void* kvaddr = kmap(pages[0]); unsigned long baddr = virt_to_bus(kaddr); kunmap(pages[0]); page_cache_release(pages[0]); //... data is page-aligned and was locked in userspace with mlock. There is some address in baddr, but the device does not write to the correct location and sometimes causes kernel freezes. Can someone tell me, what is wrong with this code?TheI device works with a address, that was received in different way (closed source driver). I use 32 bit Ubuntu with an 2.6.32 kernel.

2 2

Enabling USB OTG
by madav maddy Oct. 10, 2011

Oct. 10, 2011

Hi Experts, I am newbie and trying to enable usb OTG support in Android linux kernel, can someone please give me the pointers to proceed with this. The hardware on which android kernel boots has OTG harware, so inorder to enable it at the kenel level i enabled the following configs, CONFIG_USB_SUPPORT=y CONFIG_USB_ARCH_HAS_HCD=y CONFIG_USB_ARCH_HAS_OHCI=y CONFIG_USB_ARCH_HAS_EHCI=y CONFIG_USB=y CONFIG_USB_DEBUG=y . . CONFIG_USB_EHCI_HCD=m CONFIG_USB_OHCI_HCD=m . . CONFIG_USB_OTG=y CONFIG_USB_MUSB_OTG=y CONFIG_USB_OTG_UTILS=y am using the following configuration, musb <--- usb converter <--- usb harware device. But still the hardware doesnt seems to work properly (as no new entry is created in /dev, when a usb harware device is connected to the board), Inorder to confirm that the base board drivers are working properly, i tried loading the gadget driver and connected it to the PC host, where i was able to access the device mass storage successfully. Do i need to do anything else to enable the musb to work as OTG port. Thanks, Madavan

2 1

When is to preempt safe?
by Parmenides Oct. 9, 2011

Oct. 9, 2011

Hi, Preemption has two cases: user preemption and kernel preemption. I have tow questions about them. 1. According to Love, "If the kernel is returning to user-space, it knows it is in a safe quiescent state. In other words, if it is safe to continue executing the current task, it is also safe to pick a new task to execute." What's the meaning of user preemption's safety? How can we deduce safety of schedule from the current task going on? 2. Another statement from Love is that "the kernel can preempt a task running in the kernel so long as it does not hold a lock". Why is it not safe while kernel code holding lock?

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