Debugging General Protection Fault’s

[ Please keep me in CC as I'm not subscribed to the list] Hello, I have a doubt regarding debugging general protection fault’s. I am running the driver tests on Intel(R) Core(TM)2 Duo CPU. During the tests I see system hangs after continuous occurrence of general protection fault’s. First

character driver - poll() timeout

[ Please keep me in CC as I'm not subscribed to the list] Hello, Is it possible to print the timeout value in character driver poll() API? User mode call: int poll(struct pollfd *fds, nfds_t nfds, int timeout) Kernel mode call: unsigned int driver_poll(struct file *filp, poll_table *wait)

Re: character driver - poll() timeout

On Tue, Oct 27, 2015 at 1:41 PM, Clemens Ladisch <clem...@ladisch.de> wrote: > Muni Sekhar wrote: >> Is it possible to print the timeout value in character driver poll() API? > > No. Your driver's poll callback never waits. > > Why do you think you need this valu

Re: character driver - poll() timeout

On Tue, Oct 27, 2015 at 8:48 PM, Clemens Ladisch <clem...@ladisch.de> wrote: > Muni Sekhar wrote: >> On Tue, Oct 27, 2015 at 1:41 PM, Clemens Ladisch <clem...@ladisch.de> wrote: >>> Muni Sekhar wrote: >>>> Is it possible to print the timeout value in char

Re: character driver - poll() timeout

On Wed, Oct 28, 2015 at 12:54 PM, Clemens Ladisch <clem...@ladisch.de> wrote: > Muni Sekhar wrote: >> On Tue, Oct 27, 2015 at 8:48 PM, Clemens Ladisch <clem...@ladisch.de> wrote: >>> Muni Sekhar wrote: >>>> I need to find out when exactly driver's poll ca

enable dynamic debug - doubt

[ Please keep me in CC as I'm not subscribed to the list] Hello, The behaviour of dynamic debug prints are controlled via writing to a control file in the 'debugfs' filesystem(/dynamic_debug/control). Here I would like to know what order should the echo(for eg: echo -n 'module sdhci +p' >

utility to read/write SDIO registers with CMD52s

Hi, Is there any Linux MMC stack utility to read/write SDIO registers with CMD52s? -- Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at

sdhci-pci or sdhci_pci

[ Please keep me in CC as I'm not subscribed to the list] Hello, I loaded sdhci-pci.ko, but lsmod shows it as sdhci_pci. Why is that lsmod shows wrong module name( '-' changed to '_')? # lsmod Module Size Used by sdhci_pci 23301 0 sdhci 43685

Blacklisting the default kernel drivers

[ Please keep me in CC as I'm not subscribed to the list] Hello, I am using 3.16.0-30-generic kernel and Ubuntu 14.04.2 LTS. I need to blacklist the standard Linux MMC drivers getting loaded during power-on. For that I added the below mentioned lines to “/etc/modprobe.d/blacklist.conf”, but

Re: kfree a pointer "from the middle" causing protection faults

On Wed, Sep 2, 2015 at 9:39 PM, Jeff Epler <jep...@unpythonic.net> wrote: > On Wed, Sep 02, 2015 at 08:32:15PM +0530, Muni Sekhar wrote: >> [ Please keep me in CC as I'm not subscribed to the list] >> >> Hello, >> >> >> I am getting protectio

kfree a pointer "from the middle" causing protection faults

[ Please keep me in CC as I'm not subscribed to the list] Hello, I am getting protection faults in different kernel modules if I try to free a pointer "from the middle" for example, look at the following code: u8 *buf; buf = kzalloc( 100 , GFP_KERNEL ); … buf = buf + 50; … Kfree(buf);

“modprobe –r” not removing the modules it depends

[ Please keep me in CC as I'm not subscribed to the list] Hello, I noticed that “modprobe –r” not removing the modules it depends even though it is unused. What might be the reason for this? -- Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the

Re: enable dynamic debug - doubt

On Thu, Nov 19, 2015 at 2:38 AM, Peter Hurley <pe...@hurleysoftware.com> wrote: > > On 11/17/2015 07:40 AM, Muni Sekhar wrote: > > [ Please keep me in CC as I'm not subscribed to the list] > > > > Hello, > > > > The behaviour of dynamic debug prints a

Basic query regarding the scatter-gather DMA

Hi All, I have a basic query regarding the scatter-gather DMA. We have a device with scatter-gather capability. Is it okay to use normal DMA API’s for this device driver? Or driver only should use scatter-gather DMA API’s? -- Thanks, Sekhar

wait_event()\wake_up order fails?

Hi All, I have a kernel thread THREAD_A and it waits for an event by calling wait_event() API. Other thread THREAD_B wakes up the THREAD_A by calling wake_up() API. In a concurrent execution, what if the wake_up() is called before THREAD_A entering into TASK_UNINTERRUPTIBLE sleep? I have

doubt on schedule_work() - work task getting scheduled lately

Hi All, I have a doubt regarding the workqueue scheduling. I am using the workqueue for processing the Rx Interrupt data. I am calling schedule_work() on receiving the Rx interrupt from hardware. I calculated the time between calling the schedule_work() and workqueue task actually getting

How to identify the cause of " BUG: Bad page map in process python ..." kernel errors?

Hi All, I am observing the following statements in the kernel log while running driver soak tests: [ 8350.824403] BUG: Bad page map in process python pte:00c0 pmd:950a5067 [ 8351.457234] BUG: Bad page map in process python pte:34000c0 pmd:950a5067 [ 8351.458469] BUG: Bad page map

kmalloc size limit?

Hi All, I would like to know what is the maximum size limit for kmalloc() API to return a valid memory? Does the size limit varies based on the flags argument? -- Thanks, Sekhar

Re: kmalloc size limit?

On Mon, Aug 22, 2016 at 5:42 PM, Michal Hocko <mho...@kernel.org> wrote: > On Sat 20-08-16 00:09:53, Muni Sekhar wrote: >> Hi All, >> >> I would like to know what is the maximum size limit for kmalloc() API >> to return a valid memory? > > KMALLOC_MAX_CACHE_

SG: scatter-gather doubt?

Hi All, I am working on a xilinx PCIe endpoint with DMA reference block. The DMA reference block design has 2 Scatter-Gather engines, one for each DMA channel. Channel 0 is for HostMemory -> DMA_REF FIFO transfers Channel 1 is for DMA_REF FIFO -> HostMemory transfers Each scatter-gather engine

wake_up() or wake_up_interruptible()

Hi All, I am using a wait_event_interruptible() in kernel thread and waking that thread using wake_up(), and this logic is working fine. I would like to know whether it is the correct way of waking the thread which is in interruptible sleep mode? What about wake_up_interruptible() API? When

serial: uart_port->type

Hi All, For the uart_port structure’s “type”, I see the permitted types are none, 8250, 16450, 16550, 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. For FPGA based UART hardware(it has 512 bytes FIFO and supports up to 4Mbps speed) what should be the ‘type’ value? --

Re: serial: custom baud rate

On Thu, May 3, 2018 at 11:24 PM, Theodore Y. Ts'o <ty...@mit.edu> wrote: > On Thu, May 03, 2018 at 06:09:13PM +0530, Muni Sekhar wrote: >> Hi All, >> >> From include/asm-generic/termbits.h , I see baudrate can be one of the >> standard values: 50, 75, 110, 13

sound: aplay\arecord audio frame flow

[ Please keep me in CC as I'm not subscribed to the list] Hi All, Is there anyway in the kernel sound subsystem to know when the application calls ‘aplay’ and anything starts playing? Also for arecord\aplay, Is there any way from kernel's point of view to know when it receives for example the

wireless: need help to learn WiFi kernel stack

[ Please keep me in CC as I'm not subscribed to the list] Hi All, I’m planning to learn the Linux WiFi kernel stack. I’d like to know what happens in the background in the kernel when I connect to WiFi. How does a packet travels all the way from my application to kernel to air and back.

Re: serial: start_tx & buffer handling

On Fri, May 4, 2018 at 5:44 PM, loïc tourlonias <loic.tourlon...@gmail.com> wrote: > Hi > > On Fri, May 4, 2018 at 6:31 AM, Muni Sekhar <munisekhar...@gmail.com> wrote: >>> >>> On Fri, May 4, 2018 at 12:04 AM, Greg KH <g...@kroah.com> wrote: >>

linux-sound: timestamps for audio frames

[ Please keep me in CC as I'm not subscribed to the list] Hi All, >From sound driver, I am wondering if we could get the timestamps when It receives for example the first and last audio frames. Is there any way we can extract or expose that information to user mode? -- Thanks, Sekhar

serial: start_tx & buffer handling

Hi All, I’m trying to understand how user mode buffer is written to low level serial hardware registers. For this I read the kernel code and I came to know that from user mode write() API lands into kernel’s tty_write() ("drivers/tty/tty_io.c") and then it calls a uart_write()

serial: custom baud rate

Hi All, >From include/asm-generic/termbits.h , I see baudrate can be one of the standard values: 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 50, 576000, 921600, 100, 1152000, 150, 200, 250, 300, 350,

Re: serial: start_tx & buffer handling

On Fri, May 4, 2018 at 12:04 AM, Greg KH <g...@kroah.com> wrote: > On Thu, May 03, 2018 at 08:08:48PM +0530, Muni Sekhar wrote: >> Hi All, >> >> I’m trying to understand how user mode buffer is written to low level >> serial hardware registers. >> >&g

audio CODEC(CS42888) test

[ Please keep me in CC as I'm not subscribed to the list] Hi All, I’m having a sound hardware which contains an analogue audio CODEC(CS42888) and configuring the CODEC is performed over SPI bus. I noticed that linux kernel already had a driver(snd-soc-cs42xx8.ko) for this, I planned to use

uart throughput

Hi All, I’ve an uart hardware implemented on Xilinx FPGA image and it connects to host CPU(Intel based chip) on PCIe bus in Linux platform. The following parameters were fixed or varied when measuring the UART throughput in internal loopback mode(UART_RX and UART_TX pins were internally

audio CODEC(CS42888) test

[ Please keep me in CC as I'm not subscribed to the list] Hi All, I’m having a sound hardware which contains an analogue audio CODEC(CS42888) and configuring the CODEC is performed over SPI bus. I noticed that linux kernel already had a driver(snd-soc-cs42xx8.ko) for this, I planned to use

sound: aplay\arecord audio frame flow

[ Please keep me in CC as I'm not subscribed to the list] Hi All, Is there anyway in the kernel sound subsystem to know when the application calls ‘aplay’ and anything starts playing? Also for arecord\aplay, Is there any way from kernel's point of view to know when it receives for example the

Re: serial: start_tx & buffer handling

On Fri, May 4, 2018 at 12:04 AM, Greg KH wrote: > On Thu, May 03, 2018 at 08:08:48PM +0530, Muni Sekhar wrote: >> Hi All, >> >> I’m trying to understand how user mode buffer is written to low level >> serial hardware registers. >> >> For this I read the k

Re: serial: custom baud rate

On Thu, May 3, 2018 at 11:24 PM, Theodore Y. Ts'o wrote: > On Thu, May 03, 2018 at 06:09:13PM +0530, Muni Sekhar wrote: >> Hi All, >> >> From include/asm-generic/termbits.h , I see baudrate can be one of the >> standard values: 50, 75, 110, 134, 150, 200, 300, 600, 1200

wireless: need help to learn WiFi kernel stack

[ Please keep me in CC as I'm not subscribed to the list] Hi All, I’m planning to learn the Linux WiFi kernel stack. I’d like to know what happens in the background in the kernel when I connect to WiFi. How does a packet travels all the way from my application to kernel to air and back.

Re: serial: start_tx & buffer handling

On Fri, May 4, 2018 at 5:44 PM, loïc tourlonias wrote: > Hi > > On Fri, May 4, 2018 at 6:31 AM, Muni Sekhar wrote: >>> >>> On Fri, May 4, 2018 at 12:04 AM, Greg KH wrote: >>> > On Thu, May 03, 2018 at 08:08:48PM +0530, Muni Sekhar wrote: >>> &

serial: uart_port->type

Hi All, For the uart_port structure’s “type”, I see the permitted types are none, 8250, 16450, 16550, 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. For FPGA based UART hardware(it has 512 bytes FIFO and supports up to 4Mbps speed) what should be the ‘type’ value? --

linux-sound: timestamps for audio frames

[ Please keep me in CC as I'm not subscribed to the list] Hi All, >From sound driver, I am wondering if we could get the timestamps when It receives for example the first and last audio frames. Is there any way we can extract or expose that information to user mode? -- Thanks, Sekhar

serial: custom baud rate

Hi All, >From include/asm-generic/termbits.h , I see baudrate can be one of the standard values: 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 50, 576000, 921600, 100, 1152000, 150, 200, 250, 300, 350,

serial: start_tx & buffer handling

Hi All, I’m trying to understand how user mode buffer is written to low level serial hardware registers. For this I read the kernel code and I came to know that from user mode write() API lands into kernel’s tty_write() ("drivers/tty/tty_io.c") and then it calls a uart_write()

uart throughput

Hi All, I’ve an uart hardware implemented on Xilinx FPGA image and it connects to host CPU(Intel based chip) on PCIe bus in Linux platform. The following parameters were fixed or varied when measuring the UART throughput in internal loopback mode(UART_RX and UART_TX pins were internally

Re: Scheduler benchmarks

On Tue, Aug 18, 2020 at 11:45 PM peter enderborg wrote: > > On 8/18/20 7:53 PM, Muni Sekhar wrote: > > On Tue, Aug 18, 2020 at 11:06 PM Greg KH wrote: > >> On Tue, Aug 18, 2020 at 11:01:35PM +0530, Muni Sekhar wrote: > >>> On Tue, Aug 18, 2020 at 10:44 PM Greg

Scheduler benchmarks

Hi all, I’ve two identical Linux systems with only kernel differences. While doing kernel profiling with perf, I got the below mentioned metrics for Scheduler benchmarks. 1st system (older kernel version compared to the other system) benchmark result: $ perf bench sched messaging -g 64 #

Re: Scheduler benchmarks

On Tue, Aug 18, 2020 at 8:06 PM Greg KH wrote: > > On Tue, Aug 18, 2020 at 08:00:11PM +0530, Muni Sekhar wrote: > > Hi all, > > > > I’ve two identical Linux systems with only kernel differences. > > What are the differences in the kernels? > > > While

Re: Scheduler benchmarks

On Tue, Aug 18, 2020 at 8:06 PM Greg KH wrote: > > On Tue, Aug 18, 2020 at 08:00:11PM +0530, Muni Sekhar wrote: > > Hi all, > > > > I’ve two identical Linux systems with only kernel differences. > > What are the differences in the kernels? > > > While

Re: Scheduler benchmarks

On Tue, Aug 18, 2020 at 10:44 PM Greg KH wrote: > > On Tue, Aug 18, 2020 at 10:24:13PM +0530, Muni Sekhar wrote: > > On Tue, Aug 18, 2020 at 8:06 PM Greg KH wrote: > > > > > > On Tue, Aug 18, 2020 at 08:00:11PM +0530, Muni Sekhar wrote: > > > > Hi all

Re: Scheduler benchmarks

On Tue, Aug 18, 2020 at 11:06 PM Greg KH wrote: > > On Tue, Aug 18, 2020 at 11:01:35PM +0530, Muni Sekhar wrote: > > On Tue, Aug 18, 2020 at 10:44 PM Greg KH wrote: > > > > > > On Tue, Aug 18, 2020 at 10:24:13PM +0530, Muni Sekhar wrote: > > > > On T

kfree a pointer "from the middle" causing protection faults

[ Please keep me in CC as I'm not subscribed to the list] Hello, I am getting protection faults in different kernel modules if I try to free a pointer "from the middle" for example, look at the following code: u8 *buf; buf = kzalloc( 100 , GFP_KERNEL ); … buf = buf + 50; … Kfree(buf);

Re: kfree a pointer "from the middle" causing protection faults

On Wed, Sep 2, 2015 at 9:39 PM, Jeff Epler wrote: > On Wed, Sep 02, 2015 at 08:32:15PM +0530, Muni Sekhar wrote: >> [ Please keep me in CC as I'm not subscribed to the list] >> >> Hello, >> >> >> I am getting protection faults in different kernel modu

Debugging General Protection Fault’s

[ Please keep me in CC as I'm not subscribed to the list] Hello, I have a doubt regarding debugging general protection fault’s. I am running the driver tests on Intel(R) Core(TM)2 Duo CPU. During the tests I see system hangs after continuous occurrence of general protection fault’s. First

SG: scatter-gather doubt?

Hi All, I am working on a xilinx PCIe endpoint with DMA reference block. The DMA reference block design has 2 Scatter-Gather engines, one for each DMA channel. Channel 0 is for HostMemory -> DMA_REF FIFO transfers Channel 1 is for DMA_REF FIFO -> HostMemory transfers Each scatter-gather engine

How to identify the cause of " BUG: Bad page map in process python ..." kernel errors?

Hi All, I am observing the following statements in the kernel log while running driver soak tests: [ 8350.824403] BUG: Bad page map in process python pte:00c0 pmd:950a5067 [ 8351.457234] BUG: Bad page map in process python pte:34000c0 pmd:950a5067 [ 8351.458469] BUG: Bad page map

wake_up() or wake_up_interruptible()

Hi All, I am using a wait_event_interruptible() in kernel thread and waking that thread using wake_up(), and this logic is working fine. I would like to know whether it is the correct way of waking the thread which is in interruptible sleep mode? What about wake_up_interruptible() API? When

Re: kmalloc size limit?

On Mon, Aug 22, 2016 at 5:42 PM, Michal Hocko wrote: > On Sat 20-08-16 00:09:53, Muni Sekhar wrote: >> Hi All, >> >> I would like to know what is the maximum size limit for kmalloc() API >> to return a valid memory? > > KMALLOC_MAX_CACHE_SIZE Thanks Michal. >

kmalloc size limit?

Hi All, I would like to know what is the maximum size limit for kmalloc() API to return a valid memory? Does the size limit varies based on the flags argument? -- Thanks, Sekhar

Re: character driver - poll() timeout

On Tue, Oct 27, 2015 at 8:48 PM, Clemens Ladisch wrote: > Muni Sekhar wrote: >> On Tue, Oct 27, 2015 at 1:41 PM, Clemens Ladisch wrote: >>> Muni Sekhar wrote: >>>> Is it possible to print the timeout value in character driver poll() API? >>> >>&

Re: character driver - poll() timeout

On Wed, Oct 28, 2015 at 12:54 PM, Clemens Ladisch wrote: > Muni Sekhar wrote: >> On Tue, Oct 27, 2015 at 8:48 PM, Clemens Ladisch wrote: >>> Muni Sekhar wrote: >>>> I need to find out when exactly driver's poll callback returned timeout. >>> >>&

sdhci-pci or sdhci_pci

[ Please keep me in CC as I'm not subscribed to the list] Hello, I loaded sdhci-pci.ko, but lsmod shows it as sdhci_pci. Why is that lsmod shows wrong module name( '-' changed to '_')? # lsmod Module Size Used by sdhci_pci 23301 0 sdhci 43685

Blacklisting the default kernel drivers

[ Please keep me in CC as I'm not subscribed to the list] Hello, I am using 3.16.0-30-generic kernel and Ubuntu 14.04.2 LTS. I need to blacklist the standard Linux MMC drivers getting loaded during power-on. For that I added the below mentioned lines to “/etc/modprobe.d/blacklist.conf”, but

enable dynamic debug - doubt

[ Please keep me in CC as I'm not subscribed to the list] Hello, The behaviour of dynamic debug prints are controlled via writing to a control file in the 'debugfs' filesystem(/dynamic_debug/control). Here I would like to know what order should the echo(for eg: echo -n 'module sdhci +p' >

character driver - poll() timeout

[ Please keep me in CC as I'm not subscribed to the list] Hello, Is it possible to print the timeout value in character driver poll() API? User mode call: int poll(struct pollfd *fds, nfds_t nfds, int timeout) Kernel mode call: unsigned int driver_poll(struct file *filp, poll_table *wait)

Re: character driver - poll() timeout

On Tue, Oct 27, 2015 at 1:41 PM, Clemens Ladisch wrote: > Muni Sekhar wrote: >> Is it possible to print the timeout value in character driver poll() API? > > No. Your driver's poll callback never waits. > > Why do you think you need this value? I need to find out when

“modprobe –r” not removing the modules it depends

[ Please keep me in CC as I'm not subscribed to the list] Hello, I noticed that “modprobe –r” not removing the modules it depends even though it is unused. What might be the reason for this? -- Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the

Re: enable dynamic debug - doubt

On Thu, Nov 19, 2015 at 2:38 AM, Peter Hurley wrote: > > On 11/17/2015 07:40 AM, Muni Sekhar wrote: > > [ Please keep me in CC as I'm not subscribed to the list] > > > > Hello, > > > > The behaviour of dynamic debug prints are controlled via writing t

doubt on schedule_work() - work task getting scheduled lately

Hi All, I have a doubt regarding the workqueue scheduling. I am using the workqueue for processing the Rx Interrupt data. I am calling schedule_work() on receiving the Rx interrupt from hardware. I calculated the time between calling the schedule_work() and workqueue task actually getting

wait_event()\wake_up order fails?

Hi All, I have a kernel thread THREAD_A and it waits for an event by calling wait_event() API. Other thread THREAD_B wakes up the THREAD_A by calling wake_up() API. In a concurrent execution, what if the wake_up() is called before THREAD_A entering into TASK_UNINTERRUPTIBLE sleep? I have

Basic query regarding the scatter-gather DMA

Hi All, I have a basic query regarding the scatter-gather DMA. We have a device with scatter-gather capability. Is it okay to use normal DMA API’s for this device driver? Or driver only should use scatter-gather DMA API’s? -- Thanks, Sekhar

utility to read/write SDIO registers with CMD52s

Hi, Is there any Linux MMC stack utility to read/write SDIO registers with CMD52s? -- Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at

kernel projects for students

Hi all, What are some good Linux projects in kernel space for final year computer.science engineering students? Could someone help and share your ideas on this please. -- Thanks, Sekhar