Messages in this thread | | | Date | Fri, 19 Nov 1999 11:15:53 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [Patch] shm bug introduced with pagecache in 2.3.11 |
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On Fri, 19 Nov 1999, Richard Guenther wrote: > > So is there any way to fix this for 2.4? I dont see how we can > use processes and not loose performace at other places.
I looked at the thing quickly, and there _is_ actually a reasonably quick fix, and one that I would like to have for other reasons anyway: having read-write semaphores.
We don't have them, but they should not be fundamentally any worse to implement than the current semaphores are, and they have occasionally come up as useful things to have. They would certainly fit the bill for this particular problem very well (a page fault would get a read lock, while a mmap() would get a write lock - multiple page faults can happen in parallel).
The one race with multiple page faults that we have is handled nicely by the page table spinlock, which we introduced for kswapd anyway..
Linus
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