[patch 10/18] monwriter: Serialization bug for multithreaded applications.

Martin Schwidefsky
2007-08-07T11:15:30Z

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From: Melissa Howland <melissah@us.ibm.com>

Locking added so that multithreaded applications can now do writes
from different threads without the risk of storage corruption.

Signed-off-by: Melissa Howland <melissah@us.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

drivers/s390/char/monwriter.c | 6 ++++++
1 file changed, 6 insertions(+)

Index: quilt-2.6/drivers/s390/char/monwriter.c
===================================================================
--- quilt-2.6.orig/drivers/s390/char/monwriter.c
+++ quilt-2.6/drivers/s390/char/monwriter.c
@@ -17,6 +17,7 @@
#include <linux/miscdevice.h>
#include <linux/ctype.h>
#include <linux/poll.h>
+#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <asm/ebcdic.h>
#include <asm/io.h>
@@ -41,6 +42,7 @@ struct mon_private {
size_t hdr_to_read;
size_t data_to_read;
struct mon_buf *current_buf;
+ struct mutex thread_mutex;
};

/*
@@ -179,6 +181,7 @@ static int monwrite_open(struct inode *i
return -ENOMEM;
INIT_LIST_HEAD(&monpriv->list);
monpriv->hdr_to_read = sizeof(monpriv->hdr);
+ mutex_init(&monpriv->thread_mutex);
filp->private_data = monpriv;
return nonseekable_open(inode, filp);
}
@@ -209,6 +212,7 @@ static ssize_t monwrite_write(struct fil
void *to;
int rc;

+ mutex_lock(&monpriv->thread_mutex);
for (written = 0; written < count; ) {
if (monpriv->hdr_to_read) {
len = min(count - written, monpriv->hdr_to_read);
@@ -247,11 +251,13 @@ static ssize_t monwrite_write(struct fil
}
monpriv->hdr_to_read = sizeof(monpriv->hdr);
}
+ mutex_unlock(&monpriv->thread_mutex);
return written;

out_error:
monpriv->data_to_read = 0;
monpriv->hdr_to_read = sizeof(struct monwrite_hdr);
+ mutex_unlock(&monpriv->thread_mutex);
return rc;