December 2011 - kernelnewbies@kernelnewbies.org

kernel memory allocation
by J.Hwan Kim Dec. 23, 2011

Dec. 23, 2011

Hi, everyone How can I allocated contiguous kernel memory over 128MB ? When I use _get_free_pages() function, it returns error. I guess the memory size is greater than the amount which the function can allocate. Thanks in advance. Best Regards, J.Hwan Kim

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Memory barrier
by trisha yad Dec. 22, 2011

Dec. 22, 2011

Hi All, I need small clarification on memory barrier. #define smp_mb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() In case of SMP: is smp_mb() or smp_rmb() make order on current CPU or all cpu's Thanks

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GPIO driver module for Jetway NF98 board
by Joan Pau Beltran Dec. 22, 2011

Dec. 22, 2011

Hi everyone, I did not find any existing driver for the GPIO port of the Jetway NF98 mini-itx board, so I would like to write a module for that, using the gpiolib interface. Since the board documentation does not include any information about the GPIOs, I contacted the Jetway support team. However, the only answer was the attached code for Windows (NF98GPIO.c). As you can see, it seems clear how to set the pin states for output, but not how to read them in input mode. I asked again and the response was (literally): > input sample code: > { > data= ISA_RW(GPIO_BASE[pin]+0x2,highlow<<pin,1,~(1<<pin)); > } > //final exit SIO > outp(INDEX_PORT,0xaa); > return data; It makes no sense, and it is very upsetting. I would try to read from the same address used for output, but this is just an idea to be tested. Since I have not written any kernel module before, after reading the pertinent documentation about memory management, i/o port access, and gpiolib, I have some questions. 1. How should I request/release the ports mentioned in the attached file? Should I use the request_region/release_region functions from linux/ioport.h? In such case, what should I do with the returned struct resource? 2. I suppose that I should use the same addresses given by the support team, although their code is for windows. Is it ok? 3. Should/could I use the test_bit, set_bit, clear_bit functions to get, set the bit in the needed read/write functions I am writing? Or should I use the sequence 'inb - mask the value properly - outb' ? The second file attached is an skeleton of the module I am trying to write, any comments or suggestions are welcome. Thanks in advance! -- Joan Pau Beltran

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Fwd: Problem: plist_add undefined!
by Julie Sullivan Dec. 21, 2011

Dec. 21, 2011

Hi All, If you reply to this please make sure to Cc Monica Puig-Pey <puigpeym(a)unican.es> as well as kernelnewbies each time , I doubt she's subscribed. Cheers Julie ---------- Forwarded message ---------- From: Monica Puig-Pey <puigpeym(a)unican.es> Date: Tue, Dec 20, 2011 at 9:24 AM Subject: Problem: plist_add undefined! To: linux-rt-users(a)vger.kernel.org, linux-kernel(a)vger.kernel.org Hi there, As I told in previous posts in this list I'm developing drivers for the linux-rt kernel version in Ubuntu 10.04, based on 2.6.31 with rt_preempt patch. Currently I'm studying how to use priority lists (linux/plist.h) in a module. I read some pages from the Linux Kernel Development book to learn how linked list work in the kernel. I made and easy example, shown below, trying to put three elements, with their priorities, in a plist_head. Then, I had two problems: * First error: An error is produced when using the MACROs: - PLIST_HEAD_INIT(head, _lock) - PLIST_NODE_INIT(node, __prio) it says : /home/monica/Escritorio/plists/priolist.c: In function 'init_module': /home/monica/Escritorio/plists/priolist.c:67: error: expected expression before '.' token --> To solve this I used the functions: - static inline void plist_head_init(struct plist_head *head, struct spinlock *lock) - static inline void plist_node_init(struct plist_node *node, int prio) But I still have the problem with the MACRO * Second error, problem using plist_add: It says: “WARNING: "plist_add" [/home/monica/Escritorio/plists/priolist.ko] undefined! ” I made the module GPL, I don't know what am I doing wrong. Does anybody have an idea what is happening? Thanks in advance for any help, Cheers, Monica CODE: #include <linux/module.h> #include <linux/kernel.h> #include <linux/ioport.h> #include <linux/plist.h> #include <linux/spinlock.h> MODULE_LICENSE("GPL"); #define pid_miguel 1 #define fichero_miguel 1 #define prio_miguel 10 #define pid_monica 2 #define fichero_monica 1 #define prio_monica 30 #define pid_hector 3 #define fichero_hector 1 #define prio_hector 20 static DEFINE_SPINLOCK(lock); struct misdatos { int pid; int fichero; struct plist_node token_del_plist; }; int init_module(void) { struct plist_head mi_lista_de_datos; //struct spinlock lock; struct misdatos datos_miguel; struct misdatos datos_monica; struct misdatos datos_hector; struct misdatos *elemento_iterador; // Inicializo mi lista //PLIST_HEAD_INIT( mi_lista_de_datos, lock); plist_head_init( &mi_lista_de_datos, &lock); // Creo mis datos datos_miguel.pid = pid_miguel; datos_miguel.fichero = fichero_miguel; datos_monica.pid = pid_monica; datos_monica.fichero = fichero_monica; datos_hector.pid = pid_hector; datos_hector.fichero = fichero_hector; // Inicializamos los nodos CON LA PRIORIDAD //PLIST_NODE_INIT(datos_miguel.token_del_plist, prio_miguel); //PLIST_NODE_INIT(datos_monica.token_del_plist, prio_monica); //PLIST_NODE_INIT(datos_hector.token_del_plist, prio_hector); plist_node_init(&datos_miguel.token_del_plist, prio_miguel); plist_node_init(&datos_monica.token_del_plist, prio_monica); plist_node_init(&datos_hector.token_del_plist, prio_hector); // Los agnadimos plist_add(&(datos_miguel.token_del_plist), &mi_lista_de_datos); plist_add(&(datos_monica.token_del_plist), &mi_lista_de_datos); plist_add(&(datos_hector.token_del_plist), &mi_lista_de_datos); plist_for_each_entry(elemento_iterador, &mi_lista_de_datos, token_del_plist) { printk(KERN_INFO "El pid es : %d, con prioridad %d\n", elemento_iterador->pid, elemento_iterador->token_del_plist.prio); } return 0; } void cleanup_module(void) { printk(KERN_INFO "cleanup_module() called\n"); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/

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Question about RCU
by contemplating zombie Dec. 21, 2011

Dec. 21, 2011

Hi, I understand that multiple readers have to use rcu_read_lock(void) and rcu_read_unlock(void) to read data protected by rcu. However, I do not understand how the kernel distinguishes between multiple rcu protected regions. For e.g. if a region/data is protected by a mutex or spinlock, then the code is something like: int data; mutex_t/spinlock_t lock; print_data() { acquire(lock); release(lock); } Here kernel can distinguish between different regions/data using different locks used to protect it. However, the rcu_read(un)lock() do not accept any lock as a parameter. How does it manage under the hood? -Thanks.

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NFS server setup on Embedded Target
by naveen yadav Dec. 21, 2011

Dec. 21, 2011

Dear All, I have one embedded target running on ARM. I want to setup NFS server on it. http://www.citi.umich.edu/projects/nfsv4/linux/ I try nfs-utils-1.2.5.tar But this contain lot of dependency, Is there any other package we can use which is small in size similar to dropbear for ssh demons. Thanks

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Any good reference for Runtime suspend and resume
by sandeep kumar Dec. 21, 2011

Dec. 21, 2011

Hi all, I was trying to understand how runtime suspend and resume is implemented in the mmc subsystem. It would be very greatful if somebody can give good reference to understand the call stack, and sequence of runtime_suspend, claim_host, release_host operations execution. I was trying to findout good docs for mmc/SD subsystem docs but no help. -- With regards, Sandeep Kumar Anantapalli,

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3.2.0-rc1 could not find module
by Martin Smith Dec. 20, 2011

Dec. 20, 2011

I used git to down load the source code. I did: make defconfig make make modules make modules_install make install make install had problems: sh /usr/data/KERNEL/linux-stable/arch/x86/boot/install.sh 3.2.0-rc1 arch/x86/boot/bzImage \ System.map "/boot" ERROR: modinfo: could not find module autofs4 ERROR: modinfo: could not find module fcoe ERROR: modinfo: could not find module 8021q ERROR: modinfo: could not find module libfcoe ERROR: modinfo: could not find module garp ERROR: modinfo: could not find module libfc ERROR: modinfo: could not find module stp ERROR: modinfo: could not find module llc ERROR: modinfo: could not find module scsi_transport_fc ERROR: modinfo: could not find module scsi_tgt ERROR: modinfo: could not find module sunrpc ERROR: modinfo: could not find module ip6t_REJECT ERROR: modinfo: could not find module nf_conntrack_ipv6 ERROR: modinfo: could not find module xt_state ERROR: modinfo: could not find module nf_conntrack ERROR: modinfo: could not find module ip6table_filter ERROR: modinfo: could not find module ip6_tables ERROR: modinfo: could not find module ipv6 ERROR: modinfo: could not find module xfs ERROR: modinfo: could not find module exportfs ERROR: modinfo: could not find module dm_mirror ERROR: modinfo: could not find module dm_region_hash ERROR: modinfo: could not find module dm_log ERROR: modinfo: could not find module raid456 ERROR: modinfo: could not find module async_raid6_recov ERROR: modinfo: could not find module async_pq ERROR: modinfo: could not find module raid6_pq ERROR: modinfo: could not find module async_xor ERROR: modinfo: could not find module xor ERROR: modinfo: could not find module async_memcpy ERROR: modinfo: could not find module async_tx ERROR: modinfo: could not find module ppdev ERROR: modinfo: could not find module parport_pc ERROR: modinfo: could not find module parport ERROR: modinfo: could not find module sg ERROR: modinfo: could not find module i2c_piix4 ERROR: modinfo: could not find module i2c_core ERROR: modinfo: could not find module snd_intel8x0 ERROR: modinfo: could not find module snd_ac97_codec ERROR: modinfo: could not find module ac97_bus ERROR: modinfo: could not find module snd_seq ERROR: modinfo: could not find module snd_seq_device ERROR: modinfo: could not find module snd_pcm ERROR: modinfo: could not find module snd_timer ERROR: modinfo: could not find module snd ERROR: modinfo: could not find module soundcore ERROR: modinfo: could not find module snd_page_alloc ERROR: modinfo: could not find module e1000 ERROR: modinfo: could not find module ext3 ERROR: modinfo: could not find module jbd ERROR: modinfo: could not find module mbcache ERROR: modinfo: could not find module raid1 ERROR: modinfo: could not find module sd_mod ERROR: modinfo: could not find module crc_t10dif ERROR: modinfo: could not find module sr_mod ERROR: modinfo: could not find module cdrom ERROR: modinfo: could not find module ahci ERROR: modinfo: could not find module pata_acpi ERROR: modinfo: could not find module ata_generic ERROR: modinfo: could not find module ata_piix ERROR: modinfo: could not find module dm_mod It did however update grub and I had the option to boot from the new kernel. When I did boot from the new kernel, it gave the error "Could not find root device" I'm guessing that is because (amoung other things) the ext3 module was not found. When I looked at the make output a ext3.o has been built. And I can see it here: [root@bk508 linux-stable]# find . -name ext3.o ./fs/ext3/ext3.o Yet somehow the make install is not finding it. Any help would be appreciated.

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Issue with gdb 7.0 backtrace
by solmac john Dec. 20, 2011

Dec. 20, 2011

Dear All, As we know, generally, we run bt command in gdb, gdb show the seg fault location in last backtrace. I found one strange behaviour If i run bt command in gdb, at that itme, gdb didn’t show the segment fault location in backtrace by default. Can some one tell the reason and is this expected in SMP warning: Unable to find dynamic linker. GDB will be unable to debug shared library initializers and track explicitly loaded dynamic code. Core was generated by `./myapp'. Program terminated with signal 11, Segmentation fault. #0 malloc_consolidate (av=0x47600010) at malloc.c:5201 //not fault point thread running on CPU1 5201 malloc.c: No such file or directory. in malloc.c (gdb) bt #0 malloc_consolidate (av=0x47600010) at malloc.c:5201 #1 0x426eb1a8 in _int_malloc (av=0x47600010, bytes=<value optimized out>) at malloc.c:4435 gdb) info reg r0 0xfffe8ed4 4294872788 r1 0x427a8000 1115324416 r2 0x91 145 r3 0x708812d8 1887965912 r4 0x47600040 1197473856 r5 0x708812d8 1887965912 r6 0xb7e81318 3085439768 r7 0x47600040 1197473856 r8 0x476ec930 1198442800 r9 0x47600010 1197473808 r10 0x28 40 r11 0x70881130 1887965488 r12 0x47600018 1197473816 sp 0x431aeb20 0x431aeb20 lr 0x426eb1a8 1114550696 pc 0x426e819c 0x426e819c <malloc_consolidate+316> // also , program count show the CPU1 info fps 0x0 0 cpsr 0x60000010 1610612752 (gdb) info thread 225 Thread 190 0x00000000 in ?? () // real user fault point 224 Thread 132 __pthread_cond_wait (cond=0x41ddf060, mutex=0x41ddf090) Quit (gdb) thread 225 [Switching to thread 225 (Thread 190)]#0 0x00000000 in ?? () (gdb) bt #0 0x00000000 in ?? () (gdb) info reg r0 0x6de22ba0 1843538848 r1 0x476e1648 1198397000 r2 0x0 0 r3 0x0 0 r4 0x83407ef0 2202042096 r5 0x476e1648 1198397000 r6 0x68b3888 109787272 r7 0x0 0 r8 0x6de22ba0 1843538848 r9 0x6de22bf0 1843538928 r10 0x83407f44 2202042180 r11 0x6de22bd4 1843538900 r12 0x23f 575 sp 0x6de22b88 0x6de22b88 lr 0x1808774 25200500 pc 0x0 0 // program show the user fault info correctly of CPU0 fps 0x0 0 cpsr 0x20000010 536870928 Thanks, John

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MAX_PHYSADDR_BITS v/s MAX_PHYSMEM_BITS
by chandan r Dec. 20, 2011

Dec. 20, 2011

Hi all, Consider the following code snippet (for x86_64 arch) from arch/x86/include/asm/sparsemem.h: # define SECTION_SIZE_BITS 27 /* matt - 128 is convenient right now */ # define MAX_PHYSADDR_BITS 44 # define MAX_PHYSMEM_BITS 46 Also, consider the following comments (obtained from the same file), MAX_PHYSADDR_BITS 2^n: max size of physical address space MAX_PHYSMEM_BITS 2^n: how much memory we can have in that space According to my understanding MAX_PHYSMEM_BITS has to have a value less than or equal to MAX_PHYSADDR_BITS. But this is not the case for x86_64. Can someone explain what these macros really mean? Thanks, chandan r

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