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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-03-25 10:42:07 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-04-18 11:38:22 -0700
commitdde8da6cffe73dab81aca3855e717e40db35178c (patch)
tree8ba4ae7673a0106448a442033127669d8ea3658c
parentf60d231a87c5c9f23f10e69996f396d46f5bf901 (diff)
mm: Use static initialization for "srcu"
The MM-notifier code currently dynamically initializes the srcu_struct named "srcu" at subsys_initcall() time, and includes a BUG_ON() to check this initialization in do_mmu_notifier_register(). Unfortunately, there is no foolproof way to verify that an srcu_struct has been initialized, given the possibility of an srcu_struct being allocated on the stack or on the heap. This means that creating an srcu_struct_is_initialized() function is not a reasonable course of action. Nor is peppering do_mmu_notifier_register() with SRCU-specific #ifdefs an attractive alternative. This commit therefore uses DEFINE_STATIC_SRCU() to initialize this srcu_struct at compile time, thus eliminating both the subsys_initcall()-time initialization and the runtime BUG_ON(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: <linux-mm@kvack.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Vegard Nossum <vegard.nossum@oracle.com>
-rw-r--r--mm/mmu_notifier.c14
1 files changed, 1 insertions, 13 deletions
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index a7652acd2ab9..54ca54562928 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -21,7 +21,7 @@
#include <linux/slab.h>
/* global SRCU for all MMs */
-static struct srcu_struct srcu;
+DEFINE_STATIC_SRCU(srcu);
/*
* This function allows mmu_notifier::release callback to delay a call to
@@ -252,12 +252,6 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn,
BUG_ON(atomic_read(&mm->mm_users) <= 0);
- /*
- * Verify that mmu_notifier_init() already run and the global srcu is
- * initialized.
- */
- BUG_ON(!srcu.per_cpu_ref);
-
ret = -ENOMEM;
mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
if (unlikely(!mmu_notifier_mm))
@@ -406,9 +400,3 @@ void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
mmdrop(mm);
}
EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);
-
-static int __init mmu_notifier_init(void)
-{
- return init_srcu_struct(&srcu);
-}
-subsys_initcall(mmu_notifier_init);