question regarding down_interruptible

Dave Hylands dhylands at
Mon Apr 4 11:48:03 EDT 2011

Hi Vijay,

On Sun, Apr 3, 2011 at 9:27 PM, Vijay Ram Chitrapu
<chitrapu.vijayram at> wrote:
> Hi Experts,
> I have a system in which there is a only 1 user process and a
> corresponding kernel module (driver) associated with it to send and
> receive data to the user process. In the kernel module, i have a
> semaphore to protect a critical section of code during the rx and tx
> paths. However, at some instance of code execution, the
> down_interruptible returns EINTR, which means that the user process
> has received some interrupt due to which the process has come out of
> sleep due to the signal it received, due to which the kernel module
> has not got the semaphore. At this point of time, i have no idea as to
> which signal has triggered the user process to come out of the sleep.
> Is there a way in which we can know which signal has a process
> received, without registering any user defined handler to it?
> Any thoughts/ideas on debugging this problem can be of great help.
> Also please correct me if i am wrong in any of my understanding
> regarding down_interruptible.

The simplest way is to just register a signal handler for all possible
signals (in the user program) and print out which one actually

Dave Hylands
Shuswap, BC, Canada

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