On Wed, 2011-06-15 at 11:40 +0200, Tejun Heo wrote:
> Hello,
>
> On Wed, Jun 15, 2011 at 11:34:23AM +0200, Kay Sievers wrote:
> > Any idea why with the first check GET_EVENT seems, but TUR seems to
> > indicate no change?
>
> That's probably because probing logic already consumed UA. Reset
> during probe also causes UA so detection logic consumes them
> afterwards. I don't think driver can tell apart different UAs at that
> point. If the device determines to report media change after reset
> via GET_EVENT, you get a mismatch. So, it's more or less expected.
Here is a new patch. Would be great, if one of you guys can check if it
fixes the loop we are currently seeing.
Thanks,
Kay
From: Kay Sievers <kay.sievers@xxxxxxxx>
Subject: sr: check_events() ignore GET_EVENT when TUR says otherwise
Some (broken) devices return GET_EVENT at every open() which
lets udev run into a loop when the device is accessed fron an
event handler.
When GET_EVENT and TUR disagree for a few times in a row,
we ignore the GET_EVENT events, and trust only the TUR status.
This is the log of a USB stick with a (broken) fake CDROM drive:
scsi 5:0:0:0: Direct-Access SanDisk U3 Cruzer Micro 8.02 PQ: 0 ANSI: 0 CCS
sd 5:0:0:0: Attached scsi generic sg3 type 0
scsi 5:0:0:1: CD-ROM SanDisk U3 Cruzer Micro 8.02 PQ: 0 ANSI: 0
sd 5:0:0:0: [sdb] Attached SCSI removable disk
sr2: scsi3-mmc drive: 48x/48x tray
sr 5:0:0:1: Attached scsi CD-ROM sr2
sr 5:0:0:1: Attached scsi generic sg4 type 5
sr2: GET_EVENT and TUR disagree continuously, suppress GET_EVENT events
sd 5:0:0:0: [sdb] 31777279 512-byte logical blocks: (16.2 GB/15.1 GiB)
sd 5:0:0:0: [sdb] No Caching mode page present
sd 5:0:0:0: [sdb] Assuming drive cache: write through
sd 5:0:0:0: [sdb] No Caching mode page present
sd 5:0:0:0: [sdb] Assuming drive cache: write through
sdb: sdb1
Reported-By: Markus Rathgeb maggu2810@xxxxxxxxxxxxxx
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Kay Sievers <kay.sievers@xxxxxxxx>
---
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 4778e27..1b42dbd 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -229,6 +229,15 @@ static unsigned int sr_check_events(struct cdrom_device_info *cdi,
if (!(clearing & DISK_EVENT_MEDIA_CHANGE))
goto skip_tur;
+ /*
+ * Earlier GET_EVENT_STATUS_NOTIFICATION and TUR did not agree
+ * for a couple of times in a row. We rely on TUR only for this
+ * likely broken device, to prevent generating incorrect media
+ * changed events for every open().
+ */
+ if (cd->ignore_get_event)
+ events &= ~DISK_EVENT_MEDIA_CHANGE;
+
/* let's see whether the media is there with TUR */
last_present = cd->media_present;
ret = scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);
@@ -241,8 +250,19 @@ static unsigned int sr_check_events(struct cdrom_device_info *cdi,
cd->media_present = scsi_status_is_good(ret) ||
(scsi_sense_valid(&sshdr) && sshdr.asc != 0x3a);
- if (last_present != cd->media_present)
+ if (last_present != cd->media_present) {
events |= DISK_EVENT_MEDIA_CHANGE;
+ } else if (events & DISK_EVENT_MEDIA_CHANGE) {
+ if (cd->tur_mismatch > 8) {
+ printk("%s: GET_EVENT and TUR disagree continuously, "
+ "suppress GET_EVENT events\n", cd->cdi.name);
+ cd->ignore_get_event = true;
+ } else {
+ cd->tur_mismatch++;
+ }
+ } else if (!cd->ignore_get_event && cd->tur_mismatch > 0) {
+ cd->tur_mismatch = 0;
+ }
skip_tur:
if (cd->device->changed) {
events |= DISK_EVENT_MEDIA_CHANGE;
diff --git a/drivers/scsi/sr.h b/drivers/scsi/sr.h
index e036f1d..94a3215 100644
--- a/drivers/scsi/sr.h
+++ b/drivers/scsi/sr.h
@@ -41,6 +41,8 @@ typedef struct scsi_cd {
unsigned readcd_known:1; /* drive supports READ_CD (0xbe) */
unsigned readcd_cdda:1; /* reading audio data using READ_CD */
unsigned media_present:1; /* media is present */
+ unsigned ignore_get_event:1; /* get_event is unreliable, use TUR */
+ int tur_mismatch; /* nr of get_event TUR mismatches */
struct cdrom_device_info cdi;
/* We hold gendisk and scsi_device references on probe and use
* the refs on this kref to decide when to release them */
--
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