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uas: pre_reset and suspend: Fix a few races

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The purpose of uas_pre_reset is to:

1) Stop any new commands from being submitted while an externally triggered
   usb-device-reset is running
2) Wait for any pending commands to finish before allowing the usb-device-reset
   to continue

The purpose of uas_suspend is to:
2) Wait for any pending commands to finish before suspending

This commit fixes races in both paths:

1) For 1) we use scsi_block_requests, but the scsi midlayer calls queuecommand
   without holding any locks, so a queuecommand may already past the midlayer
   scsi_block_requests checks when we call it, add a check to uas_queuecommand
   to fix this

2) For 2) we were waiting for all sense-urbs to complete, there are 2 problems
   with this approach:
a) data-urbs may complete after the sense urb, so we need to check for those
   too
b) if a sense-urb completes with a iu id of READ/WRITE_READY a command is not
   yet done. We submit a new sense-urb immediately in this case, but that
   submit may fail (in which case it will get retried by uas_do_work), if this
   happens the sense_urbs anchor may become empty while the cmnd is not yet
   done

Also unblock requests on timeout, to avoid things getting stuck in that case.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hans de Goede 2014-09-13 12:26:42 +02:00 committed by Greg Kroah-Hartman
parent 4c5481efb4
commit f9dc024a2d
1 changed files with 55 additions and 6 deletions
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61
drivers/usb/storage/uas.c
View File

@ -667,6 +667,10 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd,
BUILD_BUG_ON(sizeof(struct uas_cmd_info) > sizeof(struct scsi_pointer));
/* Re-check scsi_block_requests now that we've the host-lock */
if (cmnd->device->host->host_self_blocked)
return SCSI_MLQUEUE_DEVICE_BUSY;
if ((devinfo->flags & US_FL_NO_ATA_1X) &&
(cmnd->cmnd[0] == ATA_12 || cmnd->cmnd[0] == ATA_16)) {
memcpy(cmnd->sense_buffer, usb_stor_sense_invalidCDB,
@ -1009,6 +1013,54 @@ set_alt0:
return result;
}
static int uas_cmnd_list_empty(struct uas_dev_info *devinfo)
{
unsigned long flags;
int i, r = 1;
spin_lock_irqsave(&devinfo->lock, flags);
for (i = 0; i < devinfo->qdepth; i++) {
if (devinfo->cmnd[i]) {
r = 0; /* Not empty */
break;
}
}
spin_unlock_irqrestore(&devinfo->lock, flags);
return r;
}
/*
* Wait for any pending cmnds to complete, on usb-2 sense_urbs may temporarily
* get empty while there still is more work to do due to sense-urbs completing
* with a READ/WRITE_READY iu code, so keep waiting until the list gets empty.
*/
static int uas_wait_for_pending_cmnds(struct uas_dev_info *devinfo)
{
unsigned long start_time;
int r;
start_time = jiffies;
do {
flush_work(&devinfo->work);
r = usb_wait_anchor_empty_timeout(&devinfo->sense_urbs, 5000);
if (r == 0)
return -ETIME;
r = usb_wait_anchor_empty_timeout(&devinfo->data_urbs, 500);
if (r == 0)
return -ETIME;
if (time_after(jiffies, start_time + 5 * HZ))
return -ETIME;
} while (!uas_cmnd_list_empty(devinfo));
return 0;
}
static int uas_pre_reset(struct usb_interface *intf)
{
struct Scsi_Host *shost = usb_get_intfdata(intf);
@ -1023,10 +1075,9 @@ static int uas_pre_reset(struct usb_interface *intf)
scsi_block_requests(shost);
spin_unlock_irqrestore(shost->host_lock, flags);
/* Wait for any pending requests to complete */
flush_work(&devinfo->work);
if (usb_wait_anchor_empty_timeout(&devinfo->sense_urbs, 5000) == 0) {
if (uas_wait_for_pending_cmnds(devinfo) != 0) {
shost_printk(KERN_ERR, shost, "%s: timed out\n", __func__);
scsi_unblock_requests(shost);
return 1;
}
@ -1064,9 +1115,7 @@ static int uas_suspend(struct usb_interface *intf, pm_message_t message)
struct Scsi_Host *shost = usb_get_intfdata(intf);
struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
/* Wait for any pending requests to complete */
flush_work(&devinfo->work);
if (usb_wait_anchor_empty_timeout(&devinfo->sense_urbs, 5000) == 0) {
if (uas_wait_for_pending_cmnds(devinfo) != 0) {
shost_printk(KERN_ERR, shost, "%s: timed out\n", __func__);
return -ETIME;
}