Re: 2.4.0-test10-pre3:Oops in mm/filemap.c:filemap_write_pa

From: Petr Vandrovec (VANDROVE@vc.cvut.cz)
Date: Mon Oct 23 2000 - 16:25:06 EST


On 23 Oct 00 at 13:57, Linus Torvalds wrote:
> On Mon, 23 Oct 2000, Petr Vandrovec wrote:
>
> > First page->mapping == NULL entry in syslog is dated 22:23:58, but
> > couple of entries was lost before (probably I should print only '.' for
> > each such page; this run there was more than 100 such pages)
> > Another question is why SIGCHLD was delivered to parent AFTER ftruncate,
> > but exit was invoked couple of seconds before - maybe it syncs
> > child address space to disk?
>
> exit() basically does do a msync(MSASYNC), so that could be it.

Yes. With sleep(60) no oops occur (it takes ~45 secs to exit child).
This signals to me: should not vmtruncate_list acquire mm->mmap_sem,
if it modifies page tables? I cannot find anything what prevents doing
vmtruncate in one task and filemap_sync in another - neither
page_table_lock spinlock, nor mmap_sem semaphore...
                                                Thanks,
                                                        Petr Vandrovec
                                                        vandrove@vc.cvut.cz
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