February 2012 - kernelnewbies@kernelnewbies.org

The 2.6.32 Linux kernel patches
by mzee mzee Feb. 23, 2012

Feb. 23, 2012

Hi, I'm a newbie to the Linux kernel, working on Android msm kernel. Due to the hack on kernel.org, there was re-organization of if infrastructure, as a result I couldn't find the 2.6.32 ALL incremental patches, although I found a few, after long poking around at: > http://www.kernel.org/pub/linux/kernel/v2.6/longterm/v2.6.32/incr/ The only ones there are from 27-28 to 55-56, where may find the rest? Also I'm new to git, does any one have a good tutorial on this with focus on Linux kernel development? Thanks

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SA_INTERRUPT or SA_SHIRQ
by devendra rawat Feb. 23, 2012

Feb. 23, 2012

Hi All, If I register an ISR using both the flags SA_INTERRUPT and SA_SHIRQ set, what kind of interrupt line will I get a dedicated one or a shared one ? the exact definition is request_irq(dev->pci_dev->irq, soc_intr, SA_INTERRUPT | SA_SHIRQ, MODULE_NAME, dev); thanks in advance, Devendra

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Iterating through all the processes in a module
by Arokux B. Feb. 23, 2012

Feb. 23, 2012

Hi, (for learning purposes) I would like to iterate through all the tasks in a module and output different information about them. For this task I need to lock the list of all tasks (need I?). I've seen some example in the kernel code which lock tasklist_lock. However this symbol cannot be used by modules. Its export was removed by c59923a15c12d2b3597af913bf234a0ef264a38b commit. Is there any other way I can lock the list of tasks then? Thanks

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Re: About interrupt handler
by cheneydeng Feb. 23, 2012

Feb. 23, 2012

Thanks to all of you~ ------------------ best regards！ cheneydeng ------------------ Original ------------------ From: "Zhengwang Ruan"<ruan.zhengwang(a)gmail.com>; Date: Thu, Feb 23, 2012 06:07 PM To: "kernelnewbies"<kernelnewbies(a)kernelnewbies.org>; Subject: Re: About interrupt handler -------- Original Message -------- From: cheneydeng Sent: 2012年02月22日星期三 23时38分37秒 To: kernelnewbies Subject: About interrupt handler hi all, I'm begin to learn the Kernel and i'm reading <<Linux kernel development>>.It says "This is an important point, always keep in mind that all interrupt handler has interrupted other code(possibly even another interrupt handler on a different line)".What i am not able to understand is how a interrupt handler be interrupted ? DID NOT it uninterrupted? It has more related to CPU architecture. Generally, while an interrupt handler is being executed, the handler itself can chose to disable or enable external interrupts (i.e, take x86 for example, IF bit for cflags reg controls this.). If IF is enabled, then the interrupt handler currently being executed may be interrupted and then jump to the entry for the coming interrupt. Thanks, -Zhengwang ------------------ best regards！ cheneydeng _______________________________________________ Kernelnewbies mailing list Kernelnewbies(a)kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

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About interrupt handler
by cheneydeng Feb. 23, 2012

Feb. 23, 2012

hi all, I'm begin to learn the Kernel and i'm reading <<Linux kernel development>>.It says "This is an important point, always keep in mind that all interrupt handler has interrupted other code(possibly even another interrupt handler on a different line)".What i am not able to understand is how a interrupt handler be interrupted ? DID NOT it uninterrupted? ------------------ best regards！ cheneydeng

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How to figure out the byteorder only with one byte number?
by Tao Jiang Feb. 22, 2012

Feb. 22, 2012

Hi: As far as I know, we can use an integer 0x12345678 with four bytes and bytes[4] array to figure out a machine's byteorder Is there a method use only one byte 0x01 and some shifts do the same work? Thank you. --------------- jiangtao

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Locking Yukon network driver
by Konstantin Zertsekel Feb. 22, 2012

Feb. 22, 2012

Hi Stephen, Sorry for disturbance... I am interested in Yukon driver and don't understand why neither rx_ring nor tx_ring are locked when used? I mean if the driver supports interrupt model, then ring->to_clean and ring->to_use should be locked during the updated... Can you please explaing? Thanks, --- KostaZ

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cgroup freezer
by bill4carson Feb. 22, 2012

Feb. 22, 2012

From Documentation/cgroups/freezer-subsystem.txt, the following words describe the purpose of cgroups freezer: "The cgroup freezer is useful to batch job management system which start and stop sets of tasks in order to schedule the resources of a machine according to the desires of a system administrator." IMHO, when system load is high, administrator could freeze some of cpu-hogged tasks in favor of more important ones, once system is most likely to be idle, frozen tasks could be thaw back on line. I don't know this idea is right or wrong, can somebody give me some hints about practical usage of cgroup freezer? thanks -- I am a slow learner but I will keep trying to fight for my dreams! --bill

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How to clean up buffer or cache momory?
by 黄小伟 Feb. 21, 2012

Feb. 21, 2012

Hi I encounter a problem recentely. My system supports USB strorage and other network applications. But after I put a file to usb storage, it will consume some many momory. (buffer + cache). And these buffered memory can not be reclaimed(use free command). So I want to know how to reclaim the buffer memory in a short time.

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Linux kernel : sysctl registering table under same proc name (path)
by chaitanya g Feb. 21, 2012

Feb. 21, 2012

Hello there, I am creating a sysctl kernel module to register 2 hierarchy under same proc name. For e.g. my_net | | net1 net2 | | t1 t2 So, I used register_sysctl_paths() API for registering the sysctl tables net1 net2 under path name my_net. Problem is when unregistering the tables dmesg shows a warning and call trace. # rmmod sysctl.ko # dmesg ------------[ cut here ]------------ WARNING: at kernel/sysctl.c:2270 unregister_sysctl_table+0xb1/0x120() (Tainted: P W ---------------- ) Hardware name: VMware Virtual Platform Modules linked in: sysctl(-)(U) ip6table_filter ip6_tables ebtable_nat ebtables xt_CHECKSUM iptable_mangle ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ipt_REJECT bridge autofs4 sunrpc fcoe libfcoe libfc scsi_transport_fc scsi_tgt 8021q garp stp llc cachefiles fscache ipv6 xt_physdev iptable_filter ip_tables dm_mirror dm_region_hash dm_log uinput ppdev parport_pc parport e1000 pcnet32 mii vmware_balloon sg i2c_piix4 i2c_core shpchp ext4 mbcache jbd2 vxspec(P)(U) vxio(P)(U) vxdmp(P)(U) sd_mod crc_t10dif sr_mod cdrom mptspi mptscsih mptbase scsi_transport_spi ata_generic pata_acpi ata_piix dm_mod [last unloaded: sysctl] Pid: 22463, comm: rmmod Tainted: P W ---------------- 2.6.32-71.el6.x86_64 #1 Call Trace: [<ffffffff8106b857>] warn_slowpath_common+0x87/0xc0 [<ffffffff8106b8aa>] warn_slowpath_null+0x1a/0x20 [<ffffffff81076251>] unregister_sysctl_table+0xb1/0x120 [<ffffffff810c611c>] ? stop_machine_destroy+0x4c/0x50 [<ffffffff810c621b>] ? stop_machine+0x4b/0x60 [<ffffffffa002d021>] sysctl_module_exit+0x21/0x23 [sysctl] [<ffffffff810ac706>] sys_delete_module+0x1a6/0x280 [<ffffffff8101ea88>] ? syscall_trace_enter+0x1d8/0x1e0 [<ffffffff81013387>] tracesys+0xd9/0xde ---[ end trace fee2c1c8e41aeb36 ]--- Kindly, help me to resolve this warning. Following is module. #include <linux/kernel.h> #include <linux/module.h> #include <linux/sysctl.h> static struct ctl_table_header * test_sysctl_header1; static struct ctl_table_header * test_sysctl_header2; int value1 = 0; int value2 = 1; int min = 10; int max = 20; static ctl_table test_table1[] = { { .ctl_name = CTL_UNNUMBERED, .procname = "value1", .data = &value1, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &min, .extra2 = &max }, { .ctl_name = CTL_UNNUMBERED, .procname = "value2", .data = &value2, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &min, .extra2 = &max }, { .ctl_name = 0 } }; static ctl_table test_table2[] = { { .ctl_name = CTL_UNNUMBERED, .procname = "value1", .data = &value1, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &min, .extra2 = &max }, { .ctl_name = CTL_UNNUMBERED, .procname = "value2", .data = &value2, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &min, .extra2 = &max }, { .ctl_name = 0 } }; static ctl_table test_net_table1[] = { { .ctl_name = CTL_UNNUMBERED, .procname = "test1", .mode = 0555, .child = test_table1 }, { .ctl_name = 0 } }; static ctl_table test_net_table2[] = { { .ctl_name = CTL_UNNUMBERED, .procname = "test2", .mode = 0555, .child = test_table2 }, { .ctl_name = 0 } }; static ctl_table test_root_table1[] = { { .ctl_name = CTL_UNNUMBERED, .procname = "net1", .mode = 0555, .child = test_net_table1 }, { .ctl_name = 0 } }; static ctl_table test_root_table2[] = { { .ctl_name = CTL_UNNUMBERED, .procname = "net2", .mode = 0555, .child = test_net_table2 }, { .ctl_name = 0 } }; static struct ctl_path net1_path[] = { { .procname = "my_net", .ctl_name = CTL_UNNUMBERED }, { } }; static int __init sysctl_module_init(void) { test_sysctl_header1 = register_sysctl_paths(net1_path, test_root_table1); test_sysctl_header2 = register_sysctl_paths(net1_path, test_root_table2); return 0; } static void __exit sysctl_module_exit(void) { unregister_sysctl_table(test_sysctl_header1); unregister_sysctl_table(test_sysctl_header2); } module_init(sysctl_module_init); module_exit(sysctl_module_exit); MODULE_LICENSE("GPL"); Thanks, Chaitanya

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