[patch 54/61] lock validator: special locking: mmap_sem

[Ingo Molnar]

From: Ingo Molnar <mingo@xxxxxxx>

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

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
---
 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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