Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 98481ff0 authored by James Bottomley's avatar James Bottomley
Browse files

[SCSI] Revert "sg: no need sg_open_exclusive_lock" 



This reverts commit 00b2d9d6.

This is one of four patches that was causing this bug

[  205.372823] ================================================
[  205.372901] [ BUG: lock held when returning to user space! ]
[  205.372979] 3.12.0-rc6-hw-debug-pagealloc+ #67 Not tainted
[  205.373055] ------------------------------------------------
[  205.373132] megarc.bin/5283 is leaving the kernel with locks still held!
[  205.373212] 1 lock held by megarc.bin/5283:
[  205.373285]  #0:  (&sdp->o_sem){.+.+..}, at: [<ffffffff8161e650>] sg_open+0x3a0/0x4d0

Cc: Vaughan Cao <vaughan.cao@oracle.com>
Acked-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent bafc8ad8

drivers/scsi/sg.c

+29 −5
Original line number Diff line number Diff line
@@ -105,6 +105,8 @@ static int scatter_elem_sz_prev = SG_SCATTER_SZ; 
static int sg_add(struct device *, struct class_interface *);

static void sg_remove(struct device *, struct class_interface *);



static DEFINE_SPINLOCK(sg_open_exclusive_lock);



static DEFINE_IDR(sg_index_idr);

static DEFINE_RWLOCK(sg_index_lock);	/* Also used to lock

							   file descriptor list for device */
@@ -174,6 +176,7 @@ typedef struct sg_device { /* holds the state of each scsi generic device */ 
	struct list_head sfds;

	struct rw_semaphore o_sem;	/* exclude open should hold this rwsem */

	volatile char detached;	/* 0->attached, 1->detached pending removal */

	/* exclude protected by sg_open_exclusive_lock */

	char exclude;		/* opened for exclusive access */

	char sgdebug;		/* 0->off, 1->sense, 9->dump dev, 10-> all devs */

	struct gendisk *disk;
@@ -222,6 +225,27 @@ static int sg_allow_access(struct file *filp, unsigned char *cmd) 
	return blk_verify_command(cmd, filp->f_mode & FMODE_WRITE);

}



static int get_exclude(Sg_device *sdp)

{

	unsigned long flags;

	int ret;



	spin_lock_irqsave(&sg_open_exclusive_lock, flags);

	ret = sdp->exclude;

	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);

	return ret;

}



static int set_exclude(Sg_device *sdp, char val)

{

	unsigned long flags;



	spin_lock_irqsave(&sg_open_exclusive_lock, flags);

	sdp->exclude = val;

	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);

	return val;

}



static int sfds_list_empty(Sg_device *sdp)

{

	unsigned long flags;
@@ -293,7 +317,7 @@ sg_open(struct inode *inode, struct file *filp) 
	}

	/* Since write lock is held, no need to check sfd_list */

	if (flags & O_EXCL)

		sdp->exclude = 1;	/* used by release lock */

		set_exclude(sdp, 1);



	if (sdp->detached) {

		retval = -ENODEV;
@@ -313,7 +337,7 @@ sg_open(struct inode *inode, struct file *filp) 
		retval = -ENOMEM;

sem_out:

		if (flags & O_EXCL) {

			sdp->exclude = 0;	/* undo if error */

			set_exclude(sdp, 0);	/* undo if error */

			up_write(&sdp->o_sem);

		} else

			up_read(&sdp->o_sem);
@@ -340,8 +364,8 @@ sg_release(struct inode *inode, struct file *filp) 
		return -ENXIO;

	SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));



	excl = sdp->exclude;

	sdp->exclude = 0;

	excl = get_exclude(sdp);

	set_exclude(sdp, 0);

	if (excl)

		up_write(&sdp->o_sem);

	else
@@ -2598,7 +2622,7 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v) 
			     scsidp->lun,

			     scsidp->host->hostt->emulated);

		seq_printf(s, " sg_tablesize=%d excl=%d\n",

			   sdp->sg_tablesize, sdp->exclude);

			   sdp->sg_tablesize, get_exclude(sdp));

		sg_proc_debug_helper(s, sdp);

	}

	read_unlock_irqrestore(&sg_index_lock, iflags);