Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Linux may have been causing USB disconnects

plus.google.com

Post reply on HN
Print view View original

51–60 of 123 posts

Re: Linux may have been causing USB disconnects

#51

Post by delinka »

caf wrote: post #48
delinka wrote: post #31

Earlier quoted context omitted.

Nothing there says that the hardware must be ready at or after 10ms. It simply says that software can't ask for anything before 10ms is up. Software has to wait 10ms, and then might have to wait longer.

That interpretation doesn't seem to make much sense though, because there would be no point in specifying the 10ms at all - it means nothing, and doesn't put any restrictions on anyone.

It does indeed put restrictions on the software author not to expect hardware to be ready in less than 10ms. Perhaps the specification is somewhat nonsensical. That does not permit the software author to create restrictive interpretations. IMHO, it informs the software author that flexibility should be allowed in their code.

Re: Linux may have been causing USB disconnects

#52

Post by caf »

delinka wrote: post #51
caf wrote: post #48

Earlier quoted context omitted.

That interpretation doesn't seem to make much sense though, because there would be no point in specifying the 10ms at all - it means nothing, and doesn't put any restrictions on anyone.

It does indeed put restrictions on the software author not to expect hardware to be ready in less than 10ms. Perhaps the specification is somewhat nonsensical. That does not permit the software author to create restrictive interpretations. IMHO, it informs the software author that flexibility should be allowed in their code.

But under your interpretation, the software can't expect the hardware to be ready in less than 100ms, 10s or 10 minutes either - so the value "10ms" is meaningless.

Re: Linux may have been causing USB disconnects

#53

Post by rwg »

stinos wrote: post #45
rustynails wrote: post #9

Now can someone fix the embarrassing network bug in Linux. You know, where if you access a link to a network, or access an open networked path after 255 seconds or so ... You receive a network error. It still begs belief that such a fundamental aspect of Linux is broken ... When I show Linux to newbies and this fault occurs (ie. 100% of the time), I simply say "Linux isn't perfect ..." But inside, I cringe... It occu…

not sure what you mean exactly, but one thing that has caused tons of trouble here, with sometimes the sole solution being a restart (ok our IT maintainer might be doing something worng, yet..) is the opposite: take a bunch of workstations and a bunch of servers, put home directories and data on servers then put everything together using NFS shares. Run analysis and whatnot on the data. Then make the server go down s…

That's kinda how NFS was designed to work. NFS comes from the dark ages of networking, where transient network errors were very common, even on local networks.

"man nfs" and "man mount.nfs" and search for "soft", "intr", "tcp", and "timeo". It sounds like the solution to your problem is some combination of those options.

Re: Linux may have been causing USB disconnects

#54

Post by xradionut »

annnnd wrote: post #3

Congrats! But how nobody analysed this bug for 8+ years is a bit of a mystery to me...

I can't speak for kernel developers, but when you have complex and large codebase running on a huge variety of hardware, you will have some edge cases that are rare or difficult to debug. And I don't envy the folks that have to interface directly with hardware, I have enough fun in database land...

Re: Linux may have been causing USB disconnects

#55

Post by stinos »

rwg wrote: post #53
stinos wrote: post #45

Earlier quoted context omitted.

not sure what you mean exactly, but one thing that has caused tons of trouble here, with sometimes the sole solution being a restart (ok our IT maintainer might be doing something worng, yet..) is the opposite: take a bunch of workstations and a bunch of servers, put home directories and data on servers then put everything together using NFS shares. Run analysis and whatnot on the data. Then make the server go down s…

That's kinda how NFS was designed to work. NFS comes from the dark ages of networking, where transient network errors were very common, even on local networks. "man nfs" and "man mount.nfs" and search for "soft", "intr", "tcp", and "timeo". It sounds like the solution to your problem is some combination of those options.

thanks, will put some more effort into it if it ever happens again

Re: Linux may have been causing USB disconnects

#56

Post by phaemon »

stinos wrote: post #45
rustynails wrote: post #9

Now can someone fix the embarrassing network bug in Linux. You know, where if you access a link to a network, or access an open networked path after 255 seconds or so ... You receive a network error. It still begs belief that such a fundamental aspect of Linux is broken ... When I show Linux to newbies and this fault occurs (ie. 100% of the time), I simply say "Linux isn't perfect ..." But inside, I cringe... It occu…

not sure what you mean exactly, but one thing that has caused tons of trouble here, with sometimes the sole solution being a restart (ok our IT maintainer might be doing something worng, yet..) is the opposite: take a bunch of workstations and a bunch of servers, put home directories and data on servers then put everything together using NFS shares. Run analysis and whatnot on the data. Then make the server go down s…

Check that you've assigned an FSID to each share in /etc/exports

Re: Linux may have been causing USB disconnects

#57

Post by 16s »

annnnd wrote: post #3

Congrats! But how nobody analysed this bug for 8+ years is a bit of a mystery to me...

Why is that variable set at 10? Who would question that?

The spec says 10 too. It's the "at least 10" part that was missed. That's very subtle, does not stand out and is easily over-looked unless someone is really auditing code and reading specs carefully.

Re: Linux may have been causing USB disconnects

#58

Post by danbee »

joosters wrote: post #43
rustynails wrote: post #9

Now can someone fix the embarrassing network bug in Linux. You know, where if you access a link to a network, or access an open networked path after 255 seconds or so ... You receive a network error. It still begs belief that such a fundamental aspect of Linux is broken ... When I show Linux to newbies and this fault occurs (ie. 100% of the time), I simply say "Linux isn't perfect ..." But inside, I cringe... It occu…

If you are connecting to a remote system, it could be NAT configured badly on your router. The router provided by my ISP (Virgin Media) is ruthless at closing idle TCP connections after only a few minutes. I'd see this with idle SSH logins being closed all the time. The solution (for me at least) was to ensure connections used TCP keepalives, and vastly decrease the keepalive times (various sysctl calls, I don't have…

Or just use a decent router and put the Virgin supplied thing in modem mode.

Re: Linux may have been causing USB disconnects

#59

Post by nly »

bluesign wrote: post #29

this is wrong interpretation actually. There is no "maximum" for a reason. Because it should be evaluated as "hey hardware developer, you will have guaranteed 10 ms from System Software to resume". If you don't wake up in 10ms, you are clearly violating the spec. 9.2.6.2 states: After a port is reset or resumed, the USB System Software is expected to provide a “recovery” interval of 10 ms before the device attached t…

The true intention of the spec is academic at this point. There are millions upon millions of devices out there with one interpretation and they're not changing. Linux can either increase the grace period or be tarnished as having bad USB suspend.
Post reply on HN