Messages in this thread |  | | Subject | Re: real POSIX.1b semaphores | From | Ulrich Drepper <> | Date | 20 Nov 1996 19:13:22 +0100 |
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"Theodore Y. Ts'o" <tytso@MIT.EDU> writes:
> I had read the earlier proposal to mean that named semaphores would also > go in globally accessible memory, which would have been a real problem.
Yes, this is true. But there is no such thing as read permission, write permission. Only a general permission the use the semaphore. So the use of a mapped page for semaphores might still be usable. Or has anybody a better proposal?
> Because of the security problems, I don't believe global unnamed > semaphores are useful.
But they have to be available. You can place the semaphore descriptor in a shared memory segment and make it available to other processes.
> Process local semaphores are useful for places > where you need speed, and named semaphores for global access. But if > you have global unnamed semaphores with no security, they really are > pointless....
POSIX.1 always says:
>>Either the implemenation shall support the XXX function as described above or the XXX function shall fail.<<
This means we really have to implement it.
-- Uli --------------. drepper@cygnus.com ,-. Rubensstrasse 5 Ulrich Drepper \ ,--------------------' \ 76149 Karlsruhe/Germany Cygnus Support `--' drepper@gnu.ai.mit.edu `------------------------
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