pid_task function fails to execute

pid_task function fails to execute

[conn intel]

Hello friends,

I am having issue with the pid_task function with arguments first as
userspace pid (using getpid fn) and 2nd argument PIDTYPE_PID.

"pid_task(<pid from userspace>, PIDTYPE_PID);"

Can anyone assist me what can be the cause?

Have a Good Day,
Thank you,
Ankur.

*The kernel gives exception as below:*
Unable to handle kernel NULL pointer dereference at virtual address 000001dd
pgd = c7c04000
[000001dd] *pgd=779fe031, *pte=00000000, *ppte=00000000
Internal error: Oops: 1 [#1]
last sysfs file: /sys/devices/platform/i2c-gpio.1/i2c-1/1-0048/temp1_pid
<8>Modules linked in: tmp102
<8>CPU: 0 Tainted: G W (2.6.33.2 #100)
<8>PC is at pid_task+0x18/0x44
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pid_task function fails to execute

[conn intel]

I found the issue:

one has to pass arguments to pid_task as: pid_task(find_get_pid(<pid found
using sys_getpid in userspace>) , PIDTYPE_PID);

I am trying to understand how the pid value using find_get_pid function
differs from the pid found in the userspace. It seems that they are
different and due to that kernel get exception.

Feel free to share comments.

Thank you,
Ankur.
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pid_task function fails to execute

[Dave Hylands]

Hi,

On Thu, May 5, 2011 at 1:42 AM, conn intel <connintel@gmail.com> wrote:
>
> I found the issue:
>
> one has to pass arguments to pid_task as: pid_task(find_get_pid(<pid found
> using sys_getpid in userspace>) , PIDTYPE_PID);
>
> I am trying to understand how the pid value using find_get_pid function
> differs from the pid found in the userspace. It seems that they are
> different and due to that kernel get exception.

In the kernel, the pid is like a thread-id and the tgid is the process id.

In user space, the ps command shows the tgid. The /proc table also
shows the tgid. You can see all of the pids associated with a process
by looking at /proc/999/task/888

Replace 999 with tthe tgid and 888 with the pid.

ls -1 -d /proc/*/task/*

will show all of the threads running in the system

ls -1 -d /proc/*

will show all of the processes running in the system (which is what ps shows).

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

pid_task function fails to execute

[conn intel]

On Thu, May 5, 2011 at 7:59 PM, Dave Hylands <dhylands@gmail.com> wrote:

> Hi,
>
> On Thu, May 5, 2011 at 1:42 AM, conn intel <connintel@gmail.com> wrote:
> >
> > I found the issue:
> >
> > one has to pass arguments to pid_task as: pid_task(find_get_pid(<pid
> found
> > using sys_getpid in userspace>) , PIDTYPE_PID);
> >
> > I am trying to understand how the pid value using find_get_pid function
> > differs from the pid found in the userspace. It seems that they are
> > different and due to that kernel get exception.
>
> In the kernel, the pid is like a thread-id and the tgid is the process id.
>
> In user space, the ps command shows the tgid. The /proc table also
> shows the tgid. You can see all of the pids associated with a process
> by looking at /proc/999/task/888
>
> Replace 999 with tthe tgid and 888 with the pid.
>
> ls -1 -d /proc/*/task/*
>
> will show all of the threads running in the system
>
> ls -1 -d /proc/*
>
> will show all of the processes running in the system (which is what ps
> shows).
>
> Thank you.
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