On 09/11, Kirill A. Shutemov wrote:
>
> This one is tricky. I *assume* the mm cannot be generally accessible after
> mm_users drops to zero, but I'm not entirely sure about it.
> procfs? ptrace?
Well, all I can say is that proc/ptrace look fine afaics...
This is off-topic, but how about the patch below? Different threads can
expand different vma's at the same time under read_lock(mmap_sem), so
vma_lock_anon_vma() can't help to serialize "locked_vm += grow".
Oleg.
--- x/mm/mmap.c
+++ x/mm/mmap.c
@@ -2146,9 +2146,6 @@ static int acct_stack_growth(struct vm_a
if (security_vm_enough_memory_mm(mm, grow))
return -ENOMEM;
- /* Ok, everything looks good - let it rip */
- if (vma->vm_flags & VM_LOCKED)
- mm->locked_vm += grow;
vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
return 0;
}
@@ -2210,6 +2207,8 @@ int expand_upwards(struct vm_area_struct
* against concurrent vma expansions.
*/
spin_lock(&vma->vm_mm->page_table_lock);
+ if (vma->vm_flags & VM_LOCKED)
+ mm->locked_vm += grow;
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_end = address;
anon_vma_interval_tree_post_update_vma(vma);
@@ -2281,6 +2280,8 @@ int expand_downwards(struct vm_area_stru
* against concurrent vma expansions.
*/
spin_lock(&vma->vm_mm->page_table_lock);
+ if (vma->vm_flags & VM_LOCKED)
+ mm->locked_vm += grow;
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_start = address;
vma->vm_pgoff -= grow;
--
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