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>
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index deca874..2728869 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -170,6 +170,8 @@
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 @@
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)