Subject: [folded-merged] mm-per-thread-vma-caching-fix-4.patch removed from -mm tree
To: davidlohr@xxxxxx,oleg@xxxxxxxxxx,riel@xxxxxxxxxx,torvalds@xxxxxxxxxxxxxxxxxxxx,walken@xxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Mon, 07 Apr 2014 15:04:40 -0700
The patch titled
Subject: mm,vmacache: also flush cache for VM_CLONE
has been removed from the -mm tree. Its filename was
mm-per-thread-vma-caching-fix-4.patch
This patch was dropped because it was folded into mm-per-thread-vma-caching.patch
------------------------------------------------------
From: Davidlohr Bueso <davidlohr@xxxxxx>
Subject: mm,vmacache: also flush cache for VM_CLONE
Oleg found that there is a potential race if we don't flush the task for
threads (VM_CLONE):
"Suppose we have a task T1 which has the valid vmacache,
T1->vmacache_seqnum == T1->mm->vmacache_seqnum == 0. Suppose it sleeps a
lot.
Suppose that its subthread T2 does a lot munmap's, finally
mm->vmacache_seqnum becomes zero again and T2 calls vmacache_flush_all().
T1 wakes up and does clone(CLONE_VM). The new thread T3 gets the copy of
T2's ->vmacache_seqnum and ->vmacache[].
T2 continues, vmacache_flush_all() finds T1 and does vmacache_flush(T1).
But the new thread T3 is not on the list yet, vmacache_flush_all() can't
find it.
So T3 will run with vmacache_valid() == T (till the next invalidate(mm)
of course) but its ->vmacache[] points to nowhere."
Address this by moving the flush call into copy_mm(), instead of only
having it in dup_mm().
Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff -puN kernel/fork.c~mm-per-thread-vma-caching-fix-4 kernel/fork.c
--- a/kernel/fork.c~mm-per-thread-vma-caching-fix-4
+++ a/kernel/fork.c
@@ -840,9 +840,6 @@ static struct mm_struct *dup_mm(struct t
if (mm->binfmt && !try_module_get(mm->binfmt->module))
goto free_pt;
- /* initialize the new vmacache entries */
- vmacache_flush(tsk);
-
return mm;
free_pt:
@@ -886,6 +883,9 @@ static int copy_mm(unsigned long clone_f
if (!oldmm)
return 0;
+ /* initialize the new vmacache entries */
+ vmacache_flush(tsk);
+
if (clone_flags & CLONE_VM) {
atomic_inc(&oldmm->mm_users);
mm = oldmm;
_
Patches currently in -mm which might be from davidlohr@xxxxxx are
origin.patch
mm-memoryc-update-comment-in-unmap_single_vma.patch
mm-per-thread-vma-caching.patch
mm-per-thread-vma-caching-fix-5.patch
mm-per-thread-vma-caching-fix-6.patch
mm-per-thread-vma-caching-fix-6-fix.patch
ipccompat-remove-sc_semopm-macro.patch
ipc-use-device_initcall.patch
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