mmap_lock: Change trace and locking order

Commit Message

Liam R. Howlett Sept. 3, 2021, 1:35 a.m. UTC

Print to the trace log before releasing the lock to avoid racing with
other trace log printers of the same lock type.

Signed-off-by: Liam R. Howlett <[e-mail]>
Suggested-by: Steven Rostedt (VMware) <[e-mail]>
---
 include/linux/mmap_lock.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Matthew Wilcox Sept. 3, 2021, 1:42 a.m. UTC | #1

On Fri, Sep 03, 2021 at 01:35:31AM +0000, Liam Howlett wrote:
> Print to the trace log before releasing the lock to avoid racing with
> other trace log printers of the same lock type.

Aren't you missing mmap_read_unlock_non_owner()?

Liam R. Howlett Sept. 3, 2021, 2:09 a.m. UTC | #2

* Matthew Wilcox <[e-mail]> [210902 21:43]:
> On Fri, Sep 03, 2021 at 01:35:31AM +0000, Liam Howlett wrote:
> > Print to the trace log before releasing the lock to avoid racing with
> > other trace log printers of the same lock type.
> 
> Aren't you missing mmap_read_unlock_non_owner()?

Yes I am.  I'll send out v2 shortly.

Patch

diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 0540f0156f58..5d2b343e39e7 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -101,14 +101,14 @@  static inline bool mmap_write_trylock(struct mm_struct *mm)
 
 static inline void mmap_write_unlock(struct mm_struct *mm)
 {
-	up_write(&mm->mmap_lock);
 	__mmap_lock_trace_released(mm, true);
+	up_write(&mm->mmap_lock);
 }
 
 static inline void mmap_write_downgrade(struct mm_struct *mm)
 {
-	downgrade_write(&mm->mmap_lock);
 	__mmap_lock_trace_acquire_returned(mm, false, true);
+	downgrade_write(&mm->mmap_lock);
 }
 
 static inline void mmap_read_lock(struct mm_struct *mm)
@@ -140,8 +140,8 @@  static inline bool mmap_read_trylock(struct mm_struct *mm)
 
 static inline void mmap_read_unlock(struct mm_struct *mm)
 {
-	up_read(&mm->mmap_lock);
 	__mmap_lock_trace_released(mm, false);
+	up_read(&mm->mmap_lock);
 }
 
 static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)