linux-kernel - BUG: about flush TLB during unmapping a page in memory subsystem

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Message-ID: <4df04b840610191947r2b48c2ddo45f0cd94d94a614b@mail.gmail.com>
Date:	Fri, 20 Oct 2006 10:47:49 +0800
From:	"yunfeng zhang" <zyf.zeroos@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: BUG: about flush TLB during unmapping a page in memory subsystem

In rmap.c::try_to_unmap_one of 2.6.16.29, there are some code snippets

.....
/* Nuke the page table entry. */
flush_cache_page(vma, address, page_to_pfn(page));
pteval = ptep_clear_flush(vma, address, pte);
// >>> The above line is expanded as below
// >>> pte_t __pte;
// >>> __pte = ptep_get_and_clear((__vma)->vm_mm, __address, __ptep);
// >>> flush_tlb_page(__vma, __address);
// >>> __pte;

/* Move the dirty bit to the physical page now the pte is gone. */
if (pte_dirty(pteval))
        set_page_dirty(page);
.....

It seems that they only can work on UP system.

On SMP, let's suppose the pte was clean, after A CPU executed
ptep_get_and_clear,
B CPU makes the pte dirty, which will make a fatal error to A CPU since it gets
a stale pte, isn't right?
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