[PATCH] locking/pvqspinlock: Fix a bug in qstat_read()

[PATCH] locking/pvqspinlock: Fix a bug in qstat_read()

[Pan Xinhui]

It's obviously wrong to set stat to NULL. So lets remove it.
Otherwise it is always zero when we check the latency of kick/wake

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 kernel/locking/qspinlock_stat.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h
index 7b0f1b9..8fa1165 100644
--- a/kernel/locking/qspinlock_stat.h
+++ b/kernel/locking/qspinlock_stat.h
@@ -157,7 +157,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
 		 */
 		if ((counter == qstat_pv_latency_kick) ||
 		    (counter == qstat_pv_latency_wake)) {
-			stat = 0;
 			if (kicks)
 				stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
 		}
-- 
1.9.1

Re: [PATCH] locking/pvqspinlock: Fix a bug in qstat_read()

[Waiman Long]

On 07/13/2016 06:23 AM, Pan Xinhui wrote:
> It's obviously wrong to set stat to NULL. So lets remove it.
> Otherwise it is always zero when we check the latency of kick/wake
>
> Signed-off-by: Pan Xinhui<xinhui.pan@linux.vnet.ibm.com>
> ---
>   kernel/locking/qspinlock_stat.h | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h
> index 7b0f1b9..8fa1165 100644
> --- a/kernel/locking/qspinlock_stat.h
> +++ b/kernel/locking/qspinlock_stat.h
> @@ -157,7 +157,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
>   		 */
>   		if ((counter == qstat_pv_latency_kick) ||
>   		    (counter == qstat_pv_latency_wake)) {
> -			stat = 0;
>   			if (kicks)
>   				stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
>   		}

Thanks for catching that. The statement shouldn't be there.

Reviewed-by: Waiman Long <Waiman.Long@hpe.com>

[tip:locking/core] locking/pvqspinlock: Fix a bug in qstat_read()

[tip-bot for Pan Xinhui]

Commit-ID:  c2ace36b884de9330c4149064ae8d212d2e0d9ee
Gitweb:     http://git.kernel.org/tip/c2ace36b884de9330c4149064ae8d212d2e0d9ee
Author:     Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
AuthorDate: Wed, 13 Jul 2016 18:23:34 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 10 Aug 2016 14:13:29 +0200

locking/pvqspinlock: Fix a bug in qstat_read()

It's obviously wrong to set stat to NULL. So lets remove it.
Otherwise it is always zero when we check the latency of kick/wake.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Waiman Long <Waiman.Long@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1468405414-3700-1-git-send-email-xinhui.pan@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/locking/qspinlock_stat.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h
index 22e0253..b9d0315 100644
--- a/kernel/locking/qspinlock_stat.h
+++ b/kernel/locking/qspinlock_stat.h
@@ -153,7 +153,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
 		 */
 		if ((counter == qstat_pv_latency_kick) ||
 		    (counter == qstat_pv_latency_wake)) {
-			stat = 0;
 			if (kicks)
 				stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
 		}