[PATCH v2 03/10] locking/locktorture: Replace strncmp with str_has_prefix

[PATCH v2 03/10] locking/locktorture: Replace strncmp with str_has_prefix

[Chuhong Yuan]

strncmp(str, const, len) is error-prone because len
is easy to have typo.
The example is the hard-coded len has counting error
or sizeof(const) forgets - 1.
So we prefer using newly introduced str_has_prefix
to substitute such strncmp.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
---
Changes in v2:
  - Newly detected in upstream.

 kernel/locking/locktorture.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index c513031cd7e3..8dd900247205 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -889,16 +889,16 @@ static int __init lock_torture_init(void)
 		cxt.nrealwriters_stress = 2 * num_online_cpus();
 
 #ifdef CONFIG_DEBUG_MUTEXES
-	if (strncmp(torture_type, "mutex", 5) == 0)
+	if (str_has_prefix(torture_type, "mutex"))
 		cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_RT_MUTEXES
-	if (strncmp(torture_type, "rtmutex", 7) == 0)
+	if (str_has_prefix(torture_type, "rtmutex"))
 		cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_SPINLOCK
-	if ((strncmp(torture_type, "spin", 4) == 0) ||
-	    (strncmp(torture_type, "rw_lock", 7) == 0))
+	if ((str_has_prefix(torture_type, "spin")) ||
+	    (str_has_prefix(torture_type, "rw_lock")))
 		cxt.debug_lock = true;
 #endif
 
-- 
2.20.1

Re: [PATCH v2 03/10] locking/locktorture: Replace strncmp with str_has_prefix

[Paul E. McKenney]

On Fri, Aug 02, 2019 at 09:46:56AM +0800, Chuhong Yuan wrote:
> strncmp(str, const, len) is error-prone because len
> is easy to have typo.
> The example is the hard-coded len has counting error
> or sizeof(const) forgets - 1.
> So we prefer using newly introduced str_has_prefix
> to substitute such strncmp.
> 
> Signed-off-by: Chuhong Yuan <hslester96@gmail.com>

Queued, thank you!  I updated the commit log as follows.  Please let
me know if I messed anything up.

							Thanx, Paul

------------------------------------------------------------------------

commit e2be525371b2f6790f6c1ab712c3d273fb1f2bea
Author: Chuhong Yuan <hslester96@gmail.com>
Date:   Fri Aug 2 09:46:56 2019 +0800

    locktorture: Replace strncmp() with str_has_prefix()
    
    The strncmp() function is error-prone because it is easy to get the
    length wrong, especially if the string is subject to change, especially
    given the need to account for the terminating nul byte.  This commit
    therefore substitutes the newly introduced str_has_prefix(), which
    does not require a separately specified length.
    
    Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
    Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index c513031cd7e3..8dd900247205 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -889,16 +889,16 @@ static int __init lock_torture_init(void)
 		cxt.nrealwriters_stress = 2 * num_online_cpus();
 
 #ifdef CONFIG_DEBUG_MUTEXES
-	if (strncmp(torture_type, "mutex", 5) == 0)
+	if (str_has_prefix(torture_type, "mutex"))
 		cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_RT_MUTEXES
-	if (strncmp(torture_type, "rtmutex", 7) == 0)
+	if (str_has_prefix(torture_type, "rtmutex"))
 		cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_SPINLOCK
-	if ((strncmp(torture_type, "spin", 4) == 0) ||
-	    (strncmp(torture_type, "rw_lock", 7) == 0))
+	if ((str_has_prefix(torture_type, "spin")) ||
+	    (str_has_prefix(torture_type, "rw_lock")))
 		cxt.debug_lock = true;
 #endif