| Message ID | 1544729885-30702-1-git-send-email-longman@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: Replace verify_mm_writelocked() by lockdep_assert_held_exclusive() | expand |
On 12/13/18 8:38 PM, Waiman Long wrote: > Using down_read_trylock() to check if a task holds a write lock on > a rwsem is not reliable. A task can hold a read lock on a rwsem and > down_read_trylock() can fail if a writer is waiting in the wait queue. > > So use lockdep_assert_held_exclusive() instead which can do the right > check when CONFIG_LOCKDEP is on. > > Signed-off-by: Waiman Long <longman@redhat.com> There's already a patch in mmotm removing this completely: https://www.ozlabs.org/~akpm/mmots/broken-out/mm-mmap-remove-verify_mm_writelocked.patch Vlastimil
diff --git a/mm/mmap.c b/mm/mmap.c index 6c04292..62a5593 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2962,16 +2962,6 @@ int vm_munmap(unsigned long start, size_t len) return ret; } -static inline void verify_mm_writelocked(struct mm_struct *mm) -{ -#ifdef CONFIG_DEBUG_VM - if (unlikely(down_read_trylock(&mm->mmap_sem))) { - WARN_ON(1); - up_read(&mm->mmap_sem); - } -#endif -} - /* * this is really a simplified "do_mmap". it only handles * anonymous maps. eventually we may be able to do some @@ -3002,7 +2992,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla * mm->mmap_sem is required to protect against another thread * changing the mappings in case we sleep. */ - verify_mm_writelocked(mm); + lockdep_assert_held_exclusive(&mm->mmap_sem); /* * Clear old maps. this also does some error checking for us
Using down_read_trylock() to check if a task holds a write lock on a rwsem is not reliable. A task can hold a read lock on a rwsem and down_read_trylock() can fail if a writer is waiting in the wait queue. So use lockdep_assert_held_exclusive() instead which can do the right check when CONFIG_LOCKDEP is on. Signed-off-by: Waiman Long <longman@redhat.com> --- mm/mmap.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-)