Re: [PATCH -rt] Updates-from-Jon-Masters-for-hwlat_detector.c.patch

[John Kacur]

On Mon, Nov 2, 2009 at 4:43 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> Hi,
>
> On Fri, 23 Oct 2009, John Kacur wrote:
>> I took Jon Masters' latest hwlat_detector patch for upstream, and grabbed
>> the bits that aren't currently in -rt. The patch is fairly small.
>>
>> Please consider it for the next -rt release.
>
> Not really.
>
>> diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
>> index be6553f..7191e17 100644
>> --- a/drivers/misc/hwlat_detector.c
>> +++ b/drivers/misc/hwlat_detector.c
>> @@ -262,6 +262,8 @@ static int get_sample(void *unused)
>>               /* Keep a running maximum ever recorded hardware latency */
>>               if (sample > data.max_sample)
>>                       data.max_sample = sample;
>> +
>> +             wake_up(&data.wq); /* wake up reader(s) */
>>       }
>>
>>       ret = 0;
>> @@ -299,8 +301,6 @@ static int kthread_fn(void *unused)
>>                       goto err_out;
>>               }
>>
>> -             wake_up(&data.wq); /* wake up reader(s) */
>> -
>
> This reverts -rt commit 5fc485f6341c177e9d5f641c6fb9e33ca465aa84.
>
> CONFIG_DEBUG_SPINLOCK_SLEEP resp. CONFIG_DEBUG_PREEMPT will tell you
> why this is a bad idea on -rt :)
>
> Thanks,
>
>        tglx
> --

Ugh. Thanks for catching that. To be honest not sure how it happened,
so it must be my fault. :)

Updated patch just adds the error checking from Jon Masters then,
patched against -rt.
From 06219178c632d9a949029ade1a85033629365dbf Mon Sep 17 00:00:00 2001
From: Jon Masters <jcm@xxxxxxxxxxxxxx>
Date: Thu, 22 Oct 2009 19:33:56 +0200
Subject: [PATCH] Updates from Jon Masters for hwlat_detector.c

Signed-off-by: Jon Masters <jcm@xxxxxxxxxxxxxx>
Signed-off-by: John Kacur <jkacur@xxxxxxxxxx>
---
 drivers/misc/Kconfig          |    2 +-
 drivers/misc/hwlat_detector.c |   12 ++++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 15cd6bc..35f441c 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -95,7 +95,7 @@ config IBM_ASM
 config HWLAT_DETECTOR
 	tristate "Testing module to detect hardware-induced latencies"
 	depends on DEBUG_FS
-	select RING_BUFFER
+	depends on RING_BUFFER
 	default m
 	---help---
 	  A simple hardware latency detector. Use this module to detect
diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
index be6553f..0ffb43a 100644
--- a/drivers/misc/hwlat_detector.c
+++ b/drivers/misc/hwlat_detector.c
@@ -607,7 +607,11 @@ static ssize_t  debug_enable_fwrite(struct file *filp,
 		if (!enabled)
 			goto unlock;
 		enabled = 0;
-		stop_kthread();
+		err = stop_kthread();
+		if (0 != err) {
+			printk(KERN_ERR BANNER "cannot stop kthread\n");
+			return -EFAULT;
+		}
 		wake_up(&data.wq);		/* reader(s) should return */
 	}
 unlock:
@@ -1194,9 +1198,13 @@ out:
  */
 static void detector_exit(void)
 {
+	int err;
+
 	if (enabled) {
 		enabled = 0;
-		stop_kthread();
+		err = stop_kthread();
+		if (0 != err)
+			printk(KERN_ERR BANNER "cannot stop kthread\n");
 	}
 
 	free_debugfs();
-- 
1.6.0.6