From b972216e27d1c853eced33f8638926636c606341 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 6 Aug 2014 16:08:20 -0700 Subject: mmu_notifier: add call_srcu and sync function for listener to delay call and sync MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When kernel device drivers or subsystems want to bind their lifespan to t= he lifespan of the mm_struct, they usually use one of the following methods: 1. Manually calling a function in the interested kernel module. The funct= ion call needs to be placed in mmput. This method was rejected by several ker= nel maintainers. 2. Registering to the mmu notifier release mechanism. The problem with the latter approach is that the mmu_notifier_release cal= lback is called from__mmu_notifier_release (called from exit_mmap). That functi= on iterates over the list of mmu notifiers and don't expect the release call= back function to remove itself from the list. Therefore, the callback function= in the kernel module can't release the mmu_notifier_object, which is actuall= y the kernel module's object itself. As a result, the destruction of the kernel module's object must to be done in a delayed fashion. This patch adds support for this delayed callback, by adding a new mmu_notifier_call_srcu function that receives a function ptr and calls th= at function with call_srcu. In that function, the kernel module releases its object. To use mmu_notifier_call_srcu, the calling module needs to call b= efore that a new function called mmu_notifier_unregister_no_release that as its= name implies, unregisters a notifier without calling its notifier release call= back. This patch also adds a function that will call barrier_srcu so those kern= el modules can sync with mmu_notifier. Signed-off-by: Peter Zijlstra Signed-off-by: Jérôme Glisse Signed-off-by: Oded Gabbay Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmu_notifier.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/mmu_notifier.h') diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index deca87452528..27288692241e 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -170,6 +170,8 @@ extern int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm); extern void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm); +extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn, + struct mm_struct *mm); extern void __mmu_notifier_mm_destroy(struct mm_struct *mm); extern void __mmu_notifier_release(struct mm_struct *mm); extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm, @@ -288,6 +290,10 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) set_pte_at(___mm, ___address, __ptep, ___pte); \ }) +extern void mmu_notifier_call_srcu(struct rcu_head *rcu, + void (*func)(struct rcu_head *rcu)); +extern void mmu_notifier_synchronize(void); + #else /* CONFIG_MMU_NOTIFIER */ static inline void mmu_notifier_release(struct mm_struct *mm) -- cgit v1.2.3-59-g8ed1b