Messages in this thread |  | | From | Daniel Phillips <> | Subject | Re: MM patches against 2.5.31 | Date | Thu, 29 Aug 2002 00:57:06 +0200 |
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On Thursday 29 August 2002 00:39, Andrew Morton wrote: > Daniel Phillips wrote: > > > > ... > > So there's no question that the race is lurking in 2.4. I noticed several > > more paths besides the one above that look suspicious as well. The bottom > > line is, 2.4 needs a fix along the lines of my suggestion or Christian's, > > something that can actually be proved. > > > > It's a wonder that this problem manifests so rarely in practice. > > I sort-of glanced through the 2.4 paths and it appears that in all of the > places where it could do a page_cache_get/release, that would never happen > because of other parts of the page state. > > Like: it can't be in pagecache, so we won't run writepage, and > it can't have buffers, so we won't run try_to_release_page(). > > Of course, I might have missed a path. And, well, generally: ugh.
I think it is happening. I just went sifting searching through the archives on 'oops' and '2.4'. The first one I found was:
2.4.18-xfs (xfs related?) oops report
which fits the description nicely.
The race I showed actually causes the page->count to go negative, avoiding a double free on a technicality. That doesn't make me feel much better about it. Have you got a BUG_ON(!page_count(page)) in put_page_testzero? I think we might see some action.
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