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    SubjectRe: Deadlock on the mm->mmap_sem
    Date
    From

    Looking through the do_page_fault(), I noticed there's a race in expand stack
    because expand_stack() expects the caller to have the mm-sem write-locked.

    I've attached a patch that might fix it appropriately. Alternatively, it may
    be worth applying Andrea's 00_silent-stack-overflow-10 patch which fixes this
    and something else too.

    David


    diff -uNr linux-2.4.10-pre12/include/linux/mm.h linux-rwsem/include/linux/mm.h
    --- linux-2.4.10-pre12/include/linux/mm.h Wed Sep 19 10:39:23 2001
    +++ linux-rwsem/include/linux/mm.h Wed Sep 19 10:40:48 2001
    @@ -586,11 +586,11 @@
    * before relocating the vma range ourself.
    */
    address &= PAGE_MASK;
    + spin_lock(&vma->vm_mm->page_table_lock);
    grow = (vma->vm_start - address) >> PAGE_SHIFT;
    if (vma->vm_end - address > current->rlim[RLIMIT_STACK].rlim_cur ||
    ((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->rlim[RLIMIT_AS].rlim_cur)
    - return -ENOMEM;
    - spin_lock(&vma->vm_mm->page_table_lock);
    + goto nomem;
    vma->vm_start = address;
    vma->vm_pgoff -= grow;
    vma->vm_mm->total_vm += grow;
    @@ -598,6 +598,9 @@
    vma->vm_mm->locked_vm += grow;
    spin_unlock(&vma->vm_mm->page_table_lock);
    return 0;
    + nomem:
    + spin_unlock(&vma->vm_mm->page_table_lock);
    + return -ENOMEM;
    }

    /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
    -
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