Attachment 27606 Details for Bug 64652

[patch] proposed patch for 2.4.21 (SLES8)

fix-smp-pagefault (text/plain), 1.52 KB, created by Hubert Mantel on 2005-01-13 15:33:14 UTC

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Creator: Hubert Mantel

Created: 2005-01-13 15:33:14 UTC

Size: 1.52 KB

patch

obsolete

>From: Andrea Arcangeli <andrea@suse.de>
>Subject: fix race in SMP page fault handler
>References: 49652
>
>fix race in SMP page fault handler
>
>diff -urNp linux-2.4.21/include/linux/mm.h linux-2.4.21.SUSE/include/linux/mm.h
>--- linux-2.4.21/include/linux/mm.h	2005-01-13 08:25:23.209941167 +0100
>+++ linux-2.4.21.SUSE/include/linux/mm.h	2005-01-13 08:29:05.425371867 +0100
>@@ -722,14 +722,24 @@ static inline int expand_stack(struct vm
> 	int err = -ENOMEM;
> 
> 	/*
>-	 * vma->vm_start/vm_end cannot change under us because the caller is required
>-	 * to hold the mmap_sem in write mode. We need to get the spinlock only
>-	 * before relocating the vma range ourself.
>+	 * vma->vm_start/vm_end cannot change under us because the caller
>+	 * is required to hold the mmap_sem in read mode.  We need the
>+	 * page_table_lock lock to serialize against concurrent expand_stacks.
> 	 */
> 	address &= PAGE_MASK;
> 	if (prev_vma && prev_vma->vm_end + (heap_stack_gap << PAGE_SHIFT) > address)
> 		goto out;
> 	spin_lock(&vma->vm_mm->page_table_lock);
>+ 
>+	/* already expanded while we were spinning? */
>+	if ((vma->vm_flags & VM_GROWSDOWN) && vma->vm_start <= address) {
>+		spin_unlock(vma->vm_mm->page_table_lock);
>+		return 0;
>+	} else if ((vma->vm_flags & VM_GROWSUP) && vma->vm_start >= address) {
>+		spin_unlock(vma->vm_mm->page_table_lock);
>+		return 0;
>+	}
>+
> 	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)

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