diff options
Diffstat (limited to 'include/linux/mmap_lock.h')
| -rw-r--r-- | include/linux/mmap_lock.h | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index aab8f1b28d26..8d38dcb6d044 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -73,11 +73,25 @@ static inline void mmap_assert_write_locked(struct mm_struct *mm) } #ifdef CONFIG_PER_VMA_LOCK +/* + * Drop all currently-held per-VMA locks. + * This is called from the mmap_lock implementation directly before releasing + * a write-locked mmap_lock (or downgrading it to read-locked). + * This should normally NOT be called manually from other places. + * If you want to call this manually anyway, keep in mind that this will release + * *all* VMA write locks, including ones from further up the stack. + */ static inline void vma_end_write_all(struct mm_struct *mm) { mmap_assert_write_locked(mm); - /* No races during update due to exclusive mmap_lock being held */ - WRITE_ONCE(mm->mm_lock_seq, mm->mm_lock_seq + 1); + /* + * Nobody can concurrently modify mm->mm_lock_seq due to exclusive + * mmap_lock being held. + * We need RELEASE semantics here to ensure that preceding stores into + * the VMA take effect before we unlock it with this store. + * Pairs with ACQUIRE semantics in vma_start_read(). + */ + smp_store_release(&mm->mm_lock_seq, mm->mm_lock_seq + 1); } #else static inline void vma_end_write_all(struct mm_struct *mm) {} @@ -112,16 +126,6 @@ static inline int mmap_write_lock_killable(struct mm_struct *mm) return ret; } -static inline bool mmap_write_trylock(struct mm_struct *mm) -{ - bool ret; - - __mmap_lock_trace_start_locking(mm, true); - ret = down_write_trylock(&mm->mmap_lock) != 0; - __mmap_lock_trace_acquire_returned(mm, true, ret); - return ret; -} - static inline void mmap_write_unlock(struct mm_struct *mm) { __mmap_lock_trace_released(mm, true); |