Messages in this thread |  | | Date | Tue, 19 Nov 1996 17:55:29 -0500 | From | "Theodore Y. Ts'o" <> | Subject | Re: real POSIX.1b semaphores |
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From: Ulrich Drepper <drepper@myware.rz.uni-karlsruhe.de> Date: 19 Nov 1996 04:56:43 +0100
For the sake of speed we should try to be able to handle as much as possible on user level. The both kinds a POSIX semaphore can be reduced to one form. I thought about the following but please don't take this as a well-thought design. I have not much experience with kernel programming.
- reserve two pages in the mmap area of each process. The first page is for global locks, ie.e., the very same page is shared by all processes. The second page is shared between all threads of a process (i.e., clone needs another flag).
Err.... be careful about the security issues. It should not be possible for a process which doesn't have access to a semaphore to just go into the shared page and much with the sempahores. This pretty much tosses out any idea where you use a single global page for all sempahores.....
- Ted
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