This is a very similar problem to a copy-on-write cache flushing problem that Tony Luck fixed in July 2006. In this case the do_no_page function handles a fault in an executable or library that is mmapped from an NFS file system. The code is copied into a newly reallocated page. The lazy_mmu_prot_update() function should be used to flush old entries from the icache for that page on ia64 processors. But that call is made after a set_pte_at call that makes the page accessible to other threads executing the same code. This was seen to cause application crashes when an OpenMP application ran many threads calling same functions at the same time. The first thread to reach a page starts to fault in the new code. One of the other threads overtakes the first and executes old data from the icache. That could result in bad instructions. It is more obvious when an old cache line contains prefetched non-instruction bits that result in an illegal instruction trap. The problem has only been seen on montecito processors which have separate level 2 icache and dcache. This dcache to icache coherency problem is more likely to occur there because of the much larger level 2 icache. I suspect that the non-NFS case is working because direct DMA into the new page is making the instruction cache coherent. Any file system that uses a non-DMA copy into the text page could show the same problem. Signed-off-by: Mike Stroyan <mike.stroyan@xxxxxx> diff --git a/mm/memory.c b/mm/memory.c index e7066e7..50c8848 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2291,6 +2291,7 @@ retry: entry = mk_pte(new_page, vma->vm_page_prot); if (write_access) entry = maybe_mkwrite(pte_mkdirty(entry), vma); + lazy_mmu_prot_update(entry); set_pte_at(mm, address, page_table, entry); if (anon) { inc_mm_counter(mm, anon_rss); @@ -2312,7 +2313,6 @@ retry: /* no need to invalidate: a not-present page shouldn't be cached */ update_mmu_cache(vma, address, entry); - lazy_mmu_prot_update(entry); unlock: pte_unmap_unlock(page_table, ptl); if (dirty_page) { -- Mike Stroyan, mike.stroyan@xxxxxx - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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