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authorPeter Zijlstra <peterz@infradead.org>2014-08-07 03:08:20 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-07 05:01:22 +0400
commitb972216e27d1c853eced33f8638926636c606341 (patch)
tree163addfd60315832e514fd7b2aa23cadd6fb6bf9 /include/linux/mmu_notifier.h
parent1d352bfd41e8219cdf9bebe79677700bdc38b540 (diff)
downloadlinux-b972216e27d1c853eced33f8638926636c606341.tar.xz
mmu_notifier: add call_srcu and sync function for listener to delay call and sync
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 <peterz@infradead.org> Signed-off-by: Jérôme Glisse <jglisse@redhat.com> Signed-off-by: Oded Gabbay <oded.gabbay@amd.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mmu_notifier.h')
-rw-r--r--include/linux/mmu_notifier.h6
1 files changed, 6 insertions, 0 deletions
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)