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DateMon, 09 Apr 2007 13:56:44 +0400
FromPavel Emelianov <>
Subject[PATCH] Lockdep treats down_write_trylock like regular down_write
This causes constructions like

down_write(&mm1->mmap_sem);
if (down_write_trylock(&mm2->mmap_sem)) {
...
up_write(&mm2->mmap_sem);
}
up_write(&mm1->mmap_sem);
generate a lockdep warning about circular locking dependence.

Call rwsem_acquire() with trylock set to 1.
--- ./kernel/rwsem.c.pbonrem 2007-03-06 19:09:50.000000000 +0300
+++ ./kernel/rwsem.c 2007-04-06 14:02:18.000000000 +0400
@@ -60,7 +60,7 @@ int down_write_trylock(struct rw_semapho
int ret = __down_write_trylock(sem);

if (ret == 1)
- rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
+ rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
return ret;
}

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