lkml.org 
[lkml]   [2020]   [Feb]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH tip/core/rcu 21/30] rculist: Add brackets around cond argument in __list_check_rcu macro
Date
From: Amol Grover <frextrite@gmail.com>

Passing a complex lockdep condition to __list_check_rcu results
in false positive lockdep splat due to incorrect expression
evaluation.

For example, a lockdep check condition `cond1 || cond2` is
evaluated as `!cond1 || cond2 && !rcu_read_lock_any_held()`
which, according to operator precedence, evaluates to
`!cond1 || (cond2 && !rcu_read_lock_any_held())`.
This would result in a lockdep splat when cond1 is false
and cond2 is true which is logically incorrect.

Signed-off-by: Amol Grover <frextrite@gmail.com>
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/rculist.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 9f313e4..8214cdc 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -60,9 +60,9 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
#define __list_check_rcu(dummy, cond, extra...) \
({ \
check_arg_count_one(extra); \
- RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(), \
+ RCU_LOCKDEP_WARN(!(cond) && !rcu_read_lock_any_held(), \
"RCU-list traversed in non-reader section!"); \
- })
+ })
#else
#define __list_check_rcu(dummy, cond, extra...) \
({ check_arg_count_one(extra); })
--
2.9.5
\
 
 \ /
  Last update: 2020-02-15 00:57    [W:0.184 / U:0.756 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site