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Subject[PATCH] sg: atomize check and set sdp->exclude in sg_open
Check and set sdp->exclude should be atomic when set in sg_open().

Signed-off-by: Vaughan Cao <vaughan.cao@oracle.com>
---
drivers/scsi/sg.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 25b5455..0ede08f 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -245,6 +245,21 @@ static int set_exclude(Sg_device *sdp, char val)
return val;
}

+/* Check if we can set exclude and then set, return 1 if success */
+static int try_set_exclude(Sg_device *sdp)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&sg_open_exclusive_lock, flags);
+ if (sdp->exclude) {
+ spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
+ return 0;
+ }
+ sdp->exclude = 1;
+ spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
+ return 1;
+}
+
static int sfds_list_empty(Sg_device *sdp)
{
unsigned long flags;
@@ -303,7 +318,7 @@ sg_open(struct inode *inode, struct file *filp)
goto error_out;
}
res = wait_event_interruptible(sdp->o_excl_wait,
- ((!sfds_list_empty(sdp) || get_exclude(sdp)) ? 0
: set_exclude(sdp, 1)));
+ ((!sfds_list_empty(sdp) || get_exclude(sdp)) ? 0 :
try_set_exclude(sdp)));
if (res) {
retval = res; /* -ERESTARTSYS because signal hit process */
goto error_out;
--
1.7.11.7


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