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Subject[patch 54/61] lock validator: special locking: mmap_sem
From: Ingo Molnar <mingo@elte.hu>

teach special (recursive) locking code to the lock validator. Has no
effect on non-lockdep kernels.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
kernel/exit.c | 2 +-
kernel/fork.c | 5 ++++-
2 files changed, 5 insertions(+), 2 deletions(-)

Index: linux/kernel/exit.c
===================================================================
--- linux.orig/kernel/exit.c
+++ linux/kernel/exit.c
@@ -582,7 +582,7 @@ static void exit_mm(struct task_struct *
/* more a memory barrier than a real lock */
task_lock(tsk);
tsk->mm = NULL;
- up_read(&mm->mmap_sem);
+ up_read_non_nested(&mm->mmap_sem);
enter_lazy_tlb(mm, current);
task_unlock(tsk);
mmput(mm);
Index: linux/kernel/fork.c
===================================================================
--- linux.orig/kernel/fork.c
+++ linux/kernel/fork.c
@@ -196,7 +196,10 @@ static inline int dup_mmap(struct mm_str

down_write(&oldmm->mmap_sem);
flush_cache_mm(oldmm);
- down_write(&mm->mmap_sem);
+ /*
+ * Not linked in yet - no deadlock potential:
+ */
+ down_write_nested(&mm->mmap_sem, 1);

mm->locked_vm = 0;
mm->mmap = NULL;
-
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