Messages in this thread | | | Subject | Re: Interception for a resource based scheduler | From | Arjan van de Ven <> | Date | Fri, 31 Dec 2004 08:48:56 +0100 |
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On Thu, 2004-12-30 at 22:51 -0800, selvakumar nagendran wrote: > hi, > I am using these information for the scheduler I am > developing in Linux. The scheduler selects the next > process to run based on the resources needed so that a > high priority process will not starve for a semaphore > key, file lock etc that were acquired by a low > priority process. The user may change the file > descriptor only through syscalls. If I intercept them > and update the resource history that I am maintaining, > then will the information break?
I think you missed the point. I'll reexplain:
what do you is
syscall_wrapper() { original_syscall_that_copies_the_numbers_to_userspace(); kmalloc(GFP_KERNEL); <-- can sleep copy_numbers_back_from_userspace(); }
it is REALLY easy for another thread of the userspace program that did the syscall to change IT'S OWN MEMORY where the 2 FD numbers are stored between the moment the original syscall copies them there, and the moment you *recopy* them back.
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