Hello Rajaram...and hello Mr McKinney .... I am sorry for CC-ing this e-mail to you, Mr McKinney. I have some difficulties when analyzing why set_task_state() gives different effect compared to simply use something like task_struct->state=TASK_RUNNING. Since I read your article about instruction reordering in LJ, maybe you can kindly shed a light here..... > <Raja2> Thanks for the information, although I am too new to these > concepts to appreciate them. Actually, I am not expert on this kind of issue...but since this is still related with process management, I am kinda interested to study it. > <Raja2> Thats interesting to know ! but we were able to send SIGKILL > when it is in kernel mode ? Yep, sending signal can be done anywhere, but signal handler is only executed on the way back to user space. but this doesn't neglect the fact that process which sleeps in kernel mode (interruptible, of course) can be woken up by sending it a signal. Also, you can check pending signal everytime you are woken up in kernel space and do the needed action (in other word, you can simulate "signal handler"). Check the thread between Toni, /me and Jan Hudec about the adventure on signal handling when doing network code hack :) > <Raja2> Thanks for your encouragement. But I am just a new guy who > is dreaming to reach some level :) I am interested in knowing more > about you in terms of your kernel work etc..I saw that you are > associated with Linux Journal etc. Any advice for me to develop > myself in understanding the kernel and contributing to it..? I am > just currently following the book by Robert Love :) <Raja2> Hehe, I am just a poor writer, nothing more :) Well, like the proverb says "practice makes perfect" :) But I can suggest several tips you can try: 1. Book is a great resource, but don't forget that you have the source of the kernel and can explore it freely. read and study it as many as you can. 2. Do discussion with people , especially one who is more knowledgable than you. This mailing list, #kernelnewbies IRC chatroom are good place to do discussion. You can also go to #osdev on Freenode for general OS discussion (not just Linux). The more you do discussion, the more you know your own weakness and other people's strenght. Believe it or not, just by reading postings on kernelnewbies, I study faster than reading a book! 3. Don't be afraid to do mistake when hacking the kernel. There are virtual machines to help! Recovering from even the worst system corrupt in virtual machine is just a matter of replacing the disk image with the fresh one :) 4. Never feel you're already on the top of the mountain. Once you get this sense, be aware, that's the sign your brain reject to learn something new. 5. Specialize! At the beginning, take a quick look on every OS aspect (scheduler, memory management, and so on). Once you get the basic idea of all those things, decide which one you want to specialize. yes, I see several genius people who is able to crunch every aspects of OS like chewing gum, but that's rare. So, realizing our brain's limit, go pick an OS aspect and study it deeper. naturally, as OS is a complex thing, you will slowly understand the other aspect just because it is related with the OS aspect you currently specialize at. Hope it helps regards Mulyadi -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
