linux-kernel - [PATCH v2] mmap_lock: Change trace and locking order

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Message-ID: <20210903022041.1843024-1-Liam.Howlett@oracle.com>
Date:   Fri, 3 Sep 2021 02:21:05 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>
Subject: [PATCH v2] mmap_lock: Change trace and locking order

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 <Liam.Howlett@...cle.com>
Suggested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 include/linux/mmap_lock.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 0540f0156f58..b179f1e3541a 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)
@@ -155,8 +155,8 @@ static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
 
 static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
 {
-	up_read_non_owner(&mm->mmap_lock);
 	__mmap_lock_trace_released(mm, false);
+	up_read_non_owner(&mm->mmap_lock);
 }
 
 static inline void mmap_assert_locked(struct mm_struct *mm)
-- 
2.30.2