Messages in this thread | | | Subject | Re: light weight user level semaphores | Date | Thu, 19 Apr 2001 12:51:18 +0100 (BST) | From | Alan Cox <> |
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> My lightweight-semaphores were actually even simpler in userspace: > * the userspace struct was just a signed count and a file handle. > * Uncontended case is exactly like Linus' version (i.e., down() is decl + > js, up() is incl()). > * The contention syscall was (in my implementation) an ioctl on the FH; the > FH was a special one, from a private syscall (although with the new VFS I'd > have written it as just another specialized FS, or even referred into the > SysVsem FS).
Which raises an even more interesting question. Suppose your semaphore function wanst a magic file system but was flock on a standard file ? The contention overhead is rather less nice than Linus proposal but it ought 8) to work without any kernel patches
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