On Tue, 2 Oct 2007, Andi Kleen wrote: > > > First call mmap with a low hint address, the new size you'll be wanting > > from the mremap, PROT_NONE, MAP_ANONYMOUS, -1, 0. Then call mremap with > > old address, old size, new size, MREMAP_MAYMOVE|MREMAP_FIXED, and new > > address as returned by the preparatory mmap. > > That's racy unfortunately in a multithreaded process. They would need to loop.
Perhaps. Though I don't see what your loop would be doing; and the mapping established by the first thread would only be vulnerable to another thread if that were really set on interfering (an un-FIXED mmap by another thread will keep away from the area assigned to the first). Certainly a two-stage procedure has to be weaker than one stage, but it is just how MAP_FIXED is normally used (isn't it?): first stake out an arena for all that's needed without MAP_FIXED, then fit into it the actual mappings required using MAP_FIXED. Blind use of MAP_FIXED is always in danger of unmapping something vital. But whether the two-stage procedure is good enough for Thayne's purpose, he'll have to judge for himself. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
