how many "contexts" are there?
From: Gaurav Jain <hidden>
Date: 2012-10-08 16:24:11
AFAIK, those three contexts that you mentioned are indeed the only contexts that an 'instruction' can be in. If you look at the top-voted answer on the stackoverflow question that you cited, it explains how a kernel thread executes kernel instructions in a process context. The idea of a 'thread' in Linux is very similar to that of a process. In fact, every 'thread' _is_ a process. Just that a 'thread'/'process' happens to share some resources with other threads/process (ex. stack, text section etc.). A kernel thread in addition has _no_ user-space addresses. The 'mm' pointer (which points to the user-space addresses of a process) is set to NULL for kernel threads. That is okay, because kernel threads are _not_ supposed to execute/access anything that might belong to a process/lies in user-space. For details, refer Linux Kernel Dev. by Robert Love. ~Gaurav On Mon, Oct 8, 2012 at 12:42 PM, Robert P. J. Day [off-list ref]wrote:
the standard explanation of context related to linux is that there are three "contexts" one can be in at any time: * user context * kernel, process context * kernel, interrupt context but that's clearly(?) an incomplete (or not refined enough) list, since it doesn't include kernel threads, and a quick google showed this: http://stackoverflow.com/questions/9389688/in-what-context-kernel-thread-runs-in-linux so is there a more refined or up-to-date list of contexts which explains them fairly well, including the subtle distinctions? thanks. rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ======================================================================== _______________________________________________ Kernelnewbies mailing list Kernelnewbies at kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
-- Gaurav Jain Associate Software Engineer VxVM Escalations Team, SAMG Symantec Software India Pvt. Ltd. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20121008/7391d39c/attachment.html