As far as i know, i should be able to read a regular file contents if i have the permissions to do so.Following is the output of ls -l stack for the stack file (/proc/pid/stack) for one of the processes running of my Linux system :-r--r--r-- 1 Usr1 Usr1 0 Sep 20 18:08 stackLooking at the permissions, i should be able to read that file.Although whenever i try to read the file (vi stack) as Usr1, it shows nothing but an empty file.At the same time i get the following output when i try to open the file as a root user.[] ptrace_stop+0x154/0x270[] get_signal_to_deliver+0x3dc/0x610[] do_signal+0x3f/0x8d0......I am not able to figure out what exactly is going on ? 
Unable to read /proc/pid/stack file even with proper permissions
linux;files;proc