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Kconfig set default macro bug?
by Matthias Brugger April 9, 2014

April 9, 2014

Hi all, I'm just playing with the early printk macros of the low level printk. The address of the UART port is set to a default value [1]. So if you save the config and then enter again in menuconfig, you are not able to change the value to a different default value (I suppose because Kconfig see the value as set), but there is no way to find out what the values for other UART ports would be. E.g. you have accidentally selected the wrong port. The only solution is, to disable the low level debugging functions, save the config and open it with menuconfig again. I'm not quite sure if this is the most convenient way of doing this. At least the default address should be readable from the config to change the value by hand. Does anyone know if we can consider this to be a bug? Cheers, Matthias [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/a… -- motzblog.wordpress.com

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What is the benefit of running CONFIG_SMP on single core device?
by Mj Embd April 9, 2014

April 9, 2014

-- -mj

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Cannot use USB device after compiling new kernel.
by HABI S RAVI April 9, 2014

April 9, 2014

I am using 3.14.0 kernel version. I compiled using localmodconfig. I am using Ubuntu in my Lenovo U410 Ultrabook. I can use USB mouse, keyboard, pendrives with the distro kernel 3.11.0-18-generic. I can use USB mouse in distro kernel, but cannot use the same in compiled kernel. I can plug in new pendrive in distro kernel and are automatically mounted. But i cannot mount pendrive in new kernel. The same occurs for USB keyboard. But i can mount Nexus 7 in both kernel. Here is the output of dmesg and lsusb. habisravi@U410:~$ dmesg tail [ 866.156540] audit: type=1400 audit(1397006611.192:33): apparmor="DENIED" operation="capable" profile="/usr/sbin/cupsd" pid=1113 comm="cupsd" capability=36 capname="block_suspend" [ 869.326789] usb 3-2: new low-speed USB device number 13 using xhci_hcd [ 869.515935] usb 3-2: New USB device found, idVendor=1bcf, idProduct=0007 [ 869.515949] usb 3-2: New USB device strings: Mfr=0, Product=2, SerialNumber=0 [ 869.515951] usb 3-2: Product: USB Optical Mouse [ 869.516121] usb 3-2: ep 0x81 - rounding interval to 64 microframes, ep desc says 80 microframes habisravi@U410:~$ habisravi@U410:~$ lsusb Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 003 Device 013: ID 1bcf:0007 Sunplus Innovation Technology Inc. Optical Mouse Bus 003 Device 003: ID 04f2:b2e1 Chicony Electronics Co., Ltd Bus 003 Device 004: ID 0cf3:3004 Atheros Communications, Inc. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub habisravi@U410:~$

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Where is debug_mutex_wake_waiter used? And it waits for what, I am getting oops
by Mj Embd April 9, 2014

April 9, 2014

While bringing up kernel on armv7 I am getting this error, Can anyone please help me. What could be the issue. t= Internal error: Oops: 5 [#1] PREEMPT SMP ARM t= Modules linked in: t= CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.14.0-11033-g3dee3bc-dirty #34 t= task: cf858400 ti: cf85a000 task.ti: cf85a000 t= PC is at debug_mutex_wake_waiter+0x3c/0x174 t= LR is at __mutex_unlock_slowpath+0xc4/0x188 t= pc : [<c0050a74>] lr : [<c03810e4>] psr: 00000193 sp : cf85be00 ip : 00000000 fp : 00000000 t= r10: c0525c59 r9 : 413fc0f3 r8 : 00000001 t= r7 : 00000000 r6 : c05296ec r5 : c04ec014 r4 : 00000000 t= r3 : 00000000 r2 : 00000002 r1 : 00000000 r0 : c04ec000 t= Flags: nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel0 ip : 00000000 fp : 00000000 t= Control: 10c5387d Table: 4000406a DAC: 00000015 t= Process swapper/0 (pid: 1, stack limit = 0xcf85a240) Segment kernel0 ip : 00000000 fp : 00000000 t= Stack: (0xcf85be00 to 0xcf85c000) t= be00: c04ec000 c04f4460 c03852cc c03810e4 00000000 00000000 cf8a7b40 00000000 t= be20: 00000000 c010a9b8 00000000 00000000 0000000d c04e8ae0 cf8a79d8 c038ab40 t= be40: cf8a7b40 00000000 00000000 c010baf0 00000001 cfde7c9c cf8a79d8 c010c3cc t= be60: 0000000d 00000000 c038ab40 cfde7c9c 00000000 00000001 00000000 00000001 t= be80: c046d974 cfde7b68 cfde7c84 c046d974 cfde7b3c c010c580 00000000 c046d974 t= bea0: cfde7b3c c02d33d0 cfde7ba6 cf85bec4 cfde7b3c cfde7c84 00000000 c0525d80 t= bec0: c04bb500 c02d34b8 cfde7b3c c056133c c04de060 c04d480c 00000000 cf85a000 t= bee0: 00000000 c0008818 00000012 c00563b4 00000000 c04d47a8 00000000 00000000 t= bf00: c05296f2 00000012 cf88bb80 60000113 00000000 c04f9960 00000000 c04f9960 t= bf20: 00000000 c04f995c c04f995c c04de080 00000001 c04de060 c0525d80 c04bb500 t= bf40: c04e8adc 00000079 00000000 c037b508 c0432ad4 c04de080 00000001 c04de060 t= bf60: c0525d80 c04bb500 c04e8ae0 00000079 00000000 c04bbc6c 00000001 00000001 t= bf80: c04bb500 c003ccec 00000000 c03798b8 00000000 00000000 00000000 00000000 t= bfa0: 00000000 c03798c0 00000000 c000e438 00000000 00000000 00000000 00000000 t= bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 t= bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 ffffffff ffffffff t= [<c0050a74>] (debug_mutex_wake_waiter) from [<c03810e4>] (__mutex_unlock_slowpath+0xc4/0x188) t= [<c03810e4>] (__mutex_unlock_slowpath) from [<c010a9b8>] (kernfs_add_one+0xc0/0x134)c4/0x188) t= [<c010a9b8>] (kernfs_add_one) from [<c010baf0>] (__kernfs_create_file+0x80/0x9c)134)c4/0x188) t= [<c010baf0>] (__kernfs_create_file) from [<c010c3cc>] (sysfs_add_file_mode_ns+0xa0/0x160) t= [<c010c3cc>] (sysfs_add_file_mode_ns) from [<c010c580>] (sysfs_add_file+0x18/0x20) t= [<c010c580>] (sysfs_add_file) from [<c02d33d0>] (__of_add_property_sysfs+0x64/0xb8) t= [<c02d33d0>] (__of_add_property_sysfs) from [<c02d34b8>] (__of_node_add+0x94/0xe0) t= [<c02d34b8>] (__of_node_add) from [<c04d480c>] (of_init+0x64/0xd4) t= [<c04d480c>] (of_init) from [<c0008818>] (do_one_initcall+0x34/0x158) t= [<c0008818>] (do_one_initcall) from [<c04bbc6c>] (kernel_init_freeable+0x108/0x1dc) t= [<c04bbc6c>] (kernel_init_freeable) from [<c03798c0>] (kernel_init+0x8/0xe4)/0x1dc) t= [<c03798c0>] (kernel_init) from [<c000e438>] (ret_from_fork+0x14/0x3c) t= Code: e5953014 e2855014 e1530005 0a00001d (e594300c) t= ---[ end trace 7c418b9a0bc03a79 ]---0001d (e594300c)

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Re: process page map
by Mark Einon April 9, 2014

April 9, 2014

On Sat Apr 5 17:33:23 EDT 2014, gary kong wrote: > I am looking at the /proc/self/maps file. i find that for every shared > library there are 4 sections with different permission. what are the > reasons for this ? does that mean the same library is loaded 4 times ? > e.g. > > > 7fb543e5d000-7fb54401a000 r-xp 00000000 08:01 6033115 > /lib/x86_64-linux-gnu/libc-2.17.so > 7fb54401a000-7fb54421a000 ---p 001bd000 08:01 6033115 > /lib/x86_64-linux-gnu/libc-2.17.so > 7fb54421a000-7fb54421e000 r--p 001bd000 08:01 6033115 > /lib/x86_64-linux-gnu/libc-2.17.so > 7fb54421e000-7fb544220000 rw-p 001c1000 08:01 6033115 > /lib/x86_64-linux-gnu/libc-2.17.so > 7fb544220000-7fb544225000 rw-p 00000000 00:00 0 > 7fb544225000-7fb54423a000 r-xp 00000000 08:01 6029447 > /lib/x86_64-linux-gnu/libgcc_s.so.1 > 7fb54423a000-7fb544439000 ---p 00015000 08:01 6029447 > /lib/x86_64-linux-gnu/libgcc_s.so.1 > 7fb544439000-7fb54443a000 r--p 00014000 08:01 6029447 > /lib/x86_64-linux-gnu/libgcc_s.so.1 > 7fb54443a000-7fb54443b000 rw-p 00015000 08:01 6029447 > /lib/x86_64-linux-gnu/libgcc_s.so.1 > 7fb54443b000-7fb54453e000 r-xp 00000000 08:01 6032973 > /lib/x86_64-linux-gnu/libm-2.17.so > 7fb54453e000-7fb54473d000 ---p 00103000 08:01 6032973 > /lib/x86_64-linux-gnu/libm-2.17.so > 7fb54473d000-7fb54473e000 r--p 00102000 08:01 6032973 > /lib/x86_64-linux-gnu/libm-2.17.so > 7fb54473e000-7fb54473f000 rw-p 00103000 08:01 6032973 > /lib/x86_64-linux-gnu/libm-2.17.so > > Gary Hi Gary, My details below may be a bit sketchy but it means that each library is made up of four parts - * The read ony executable part (r-xp) is the text section, containing the executable code. * The no permissions (---p) part is (probably...?) kernel specific (something to do with faster syscalls?). * The read only non-executable part (r--p) is the data segment for static, read only data and the bss. * The read write part (rw-p) is for dynamic data that the library uses. The 'pmap' command gives this info in a slightly easier to read way. Hope that helps, Mark

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about the kernelnewbies email signature
by Chan Kim April 9, 2014

April 9, 2014

Hi, How come some people's email contain the email signature shown below > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > .. while my email doesn't have it attached? Are those people explicitly inserting it? or is there any option? Thanks in advance. Chan

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RE: Debugging techniques inside kernel
by Anand Arumugam April 9, 2014

April 9, 2014

Try using strace and see if all of the different crashes have the same or similar looking call stack. Here's a link on how to use it in case you didn't know already: http://stackoverflow.com/questions/174942/how-to-use-strace -----Original Message----- From: manty kuma Sent: 7/7/2013 8:06 PM To: Valdis Kletnieks Cc: kernelnewbies(a)kernelnewbies.org Subject: Re: Debugging techniques inside kernel Hi Valdis, Thanks for the info. I have serial logs (using minicom). This is not helping me much as randomly memory is getting crashed and everytime it changes. Even the logs before the crash are varying everytime. On Mon, Jul 8, 2013 at 11:49 AM, <Valdis.Kletnieks(a)vt.edu> wrote: On Mon, 08 Jul 2013 11:22:16 +0900, manty kuma said: > For ex : *CONFIG_SLUB_DEBUG_ON, *CONFIG_DMA_API_DEBUG > I am just told to use these configs and check. Not sure how to use them > effectively. Please share if you are aware of these kind of configs and how > to use them. To have them at one place it would be useful for debugging > beginners like me. Most _DEBUG config options are set-and-forget - you turn them on and there's no further configuration needed. They enable additional code that does additional sanity checking and if it finds a problem, it issues a printk() or a stack dump or similar which shows up in dmesg. If you're chasing memory corruption, it may be useful to use netconsole or a serial console to send out all the printk() output in real time, as often an error will be detected but the system will panic()/crash/hang in a way that your local syslog daemon is unable to write the message to disk. (I'm told that on newer UEFI based systems, you can use pstore in a similar fashion, but have not tried it myself yet).

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Ctrl-C doesn't work in the shell
by Chan Kim April 9, 2014

April 9, 2014

Hi, When I'm on a sheel on LCD using USB keyboard, all works fine (except another important problem..) but Ctrl-C key doesn't work. When I press ctrl-C, '^C' is displayed on the screen (prompt line), but doesn't have the effect of killing the job. For example, I start ping and it displays the response every second, but even if I press Ctrl-C, it contiues pinging. What should I do? Thanks! Chan

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USB device not mounting
by HABI S RAVI April 9, 2014

April 9, 2014

Hi, I compiled Linux kernel from the source tree and booted from it. I used the config from my distribution. After booting, I can mount only those USB devices that i have mounted with the distribution kernel. I cannot mount new USB devices.

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2.6.10 no boot
by Marcello Stanisci April 8, 2014

April 8, 2014

Dear All, I built a linux kernel 2.6.10. When grub tries to execute it the system shows the message: Uncompressing Linux.. and then reboots in a very Spartan way. My suspects are that a modern bootloader tries to boot an older (although respectful) kernel. In facts grub does some preliminar, and mysterious to me, work prior to launch the kernel. In the following links you will find my .config and an excerpt of my grub.cfg. As an additional information, the same happens on two machines of mine (both having a debian wheezy), so the problem should not be related to hardware. .config --> http://www.polarhome.com:753/~marcello/.config grub.cfg --> http://www.polarhome.com:753/~marcello/grub.cfg In just one word: HELP Thanks in Advance.

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