Hi all, I've a strange problem with the USB subsystem, under kernel 3.6, this was not happening under 3.5. The system is Fedora, so I'll use their kernel numbers, and the related bug report is this: https://bugzilla.redhat.com/show_bug.cgi?id=866166 I've some USB hubs cascaded in order to have 10 ports available. Two configurations: one is with 3 hubs, 4 ports each, where 2 hubs are connected to the first one. Second configuration is similar, it only uses 1 hubs with 7 ports followed by a 5 ports one. To the resulting 10 ports are connected to 10 USB hard disks. This is a "feasibility study" on the possibility to create a storage device in this condition. The 10 HDDs are combined in RAID-6. Now, until kernel 3.5.6, everything was working fine, I can achieve around 43MB/sec transfer rate (read) from such setup, with high reliability. Of course, some times one HDD would flight away, but nothing really serious as a problem. In fact this was one of the point I wanted to check. Since kernel 3.6.x, after short time accessing the RAID (or in parallel the 10 HDDs, independently from the md layer), I get error -110 from the USB subsystem and everything dies. It seems to me, but I'm not sure, reading a single HDD does not lead to this problem. Furthermore, the USB ehci subsystem does not work any more, even after waiting for the usual timeouts, connecting a USB stick to some other USB port in the PC results in absolute nothing. Removing ehci, via sysfs since it is compiled in, result in a system working, but at USB 1.1 speed. My suspect is that something in kernel 3.6 changed the behaviour under load of the USB subsystem, showing up only in such extreme cases, I guess. Probably it is a borderline test case, nevertheless, still a failure. The USB HDD controller are JMicron, I do not know if it does matter. Any idea or suggestion on how to test further? Thanks a lot in advance, bye, -- piergiorgio -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
