Stefan Richter wrote: > On Jan 04 Otto Meta wrote: > > Otto Meta wrote: > > > The single mutex for the sr module, introduced as a BKL replacement, > > > globally serialises all sr ioctls, which hurts multi-drive performance. > > > > > > This patch replaces sr_mutex with per-device mutexes in struct scsi_cd, > > > allowing concurrent ioctls on different sr devices. > > > > Unfortunately it wasn't as easy as that. The patch seems to introduce > > a race condition that corrupts a drive's state under certain circumstances. > > > > When two drives (e.g. sr0 and sr1) are attached to the same IDE cable, one > > drive has its door locked, which will usually be the case after any operation > > on the drive with inserted media (and whenever it feels like it, even with > > dev.cdrom.lock=0), and the other drive is unlocked, then executing > > > > $ eject sr0 & eject sr1 > > > > will eject the unlocked drive and the locked drive will return > > > > eject: unable to eject, last error: Inappropriate ioctl for device > > > > > > Other drivers down the road probably don't expect concurrent ioctls, so this > > patch cannot be applied safely at this time. Sorry about the noise. > > > > For the record: Tested with kernels 3.2.35 and 3.8.0-rc1, using IDE CD/DVD > > drives connected via the drivers ata_piix and pata_pdc202xx_old. > > As yo may have seen in the mailinglist archive, when Wakko and I tested > with sr_mutex removed without any replacement, we were not able to trigger > any race condition. However, we certainly did not attempt this very > particular test (two drives on the same PATA cable, one locked and one > unlocked, and "eject" called on both of them at the same time). I wonder > if this is a PATA idiosyncrasy. > > I will see whether I can do some tests tomorrow. I can easily test master > and slave PATA drives on a single cable behind a PATA-to-1394 bridge; but > testing two drives on a single cable behind a PATA-to-PCI controller would > be a bit more involved because the case of my PATA-equipped Linux PC is > rather cramped. I myself have not tried this specific test. I do not have any systems with 2 PATA DVDroms on the same cable. The only system I have that has PATA, the drives are on seperate cables with nothing else on the cable. My other system is all SATA. I have no other systems with more than 1 CD/DVD drive. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
