st_open() is taking a global mutex 'st_mutex' to protect
against concurrent calls to st_open(). However, as
st_open() might take quite some time before returning,
_any_ open to _any_ st device will be blocked during
that time.
Seeing that all critical sections are already protected
by individual spinlocks 'st_mutex' doesn't serve any
purpose and can be removed, unblocking concurrent
accesses.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Cc: James Bottomley <jbottomley@xxxxxxxxxxxxx>
Cc: Kai Mäkisara <Kai.Makisara@xxxxxxxxxxx>
Cc: Lee Duncan <lduncan@xxxxxxxx>
---
drivers/scsi/st.c | 8 ++------
1 files changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index e41998c..c6c172e 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -74,7 +74,6 @@ static const char *verstr = "20101219";
#include "st_options.h"
#include "st.h"
-static DEFINE_MUTEX(st_mutex);
static int buffer_kbs;
static int max_sg_segs;
static int try_direct_io = TRY_DIRECT_IO;
@@ -1188,7 +1187,6 @@ static int st_open(struct inode *inode, struct file *filp)
int dev = TAPE_NR(inode);
char *name;
- mutex_lock(&st_mutex);
/*
* We really want to do nonseekable_open(inode, filp); here, but some
* versions of tar incorrectly call lseek on tapes and bail out if that
@@ -1197,7 +1195,6 @@ static int st_open(struct inode *inode, struct file *filp)
filp->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
if (!(STp = scsi_tape_get(dev))) {
- mutex_unlock(&st_mutex);
return -ENXIO;
}
@@ -1208,7 +1205,6 @@ static int st_open(struct inode *inode, struct file *filp)
if (STp->in_use) {
write_unlock(&st_dev_arr_lock);
scsi_tape_put(STp);
- mutex_unlock(&st_mutex);
DEB( printk(ST_DEB_MSG "%s: Device already in use.\n", name); )
return (-EBUSY);
}
@@ -1262,16 +1258,16 @@ static int st_open(struct inode *inode, struct file *filp)
retval = (-EIO);
goto err_out;
}
- mutex_unlock(&st_mutex);
return 0;
err_out:
normalize_buffer(STp->buffer);
+ write_lock(&st_dev_arr_lock);
STp->in_use = 0;
+ write_unlock(&st_dev_arr_lock);
scsi_tape_put(STp);
if (resumed)
scsi_autopm_put_device(STp->device);
- mutex_unlock(&st_mutex);
return retval;
}
--
1.7.4.2
--
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