Commit-ID: dde8da6cffe73dab81aca3855e717e40db35178c Gitweb: http://git.kernel.org/tip/dde8da6cffe73dab81aca3855e717e40db35178c Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Sat, 25 Mar 2017 10:42:07 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Tue, 18 Apr 2017 11:38:22 -0700 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@xxxxxxxxxxxxxxxxxx> Cc: <linux-mm@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx> Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx> --- mm/mmu_notifier.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-) diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index a7652ac..54ca545 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); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
