Messages in this thread | | | Date | Tue, 22 Aug 2006 17:59:50 +0200 | From | Joerg Sommrey <> | Subject | Re: PROBLEM: FUSE unmount breaks serial terminal line |
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On Tue, Aug 22, 2006 at 10:57:15AM +0200, Miklos Szeredi wrote: > > > > something in FUSE breaks serial devices. I found this issue > > > > using gphotofs, don't know if any other FUSE impementation has similar > > > > effects. The problem is: from the moment the FUSE filesystem is unmounted, > > > > a process that read()s on a serial device /dev/ttyS? gets an EOF > > > > returncode. > > > > > > > > Here is the tail of the output from "strace -tt cat /dev/ttyS0" when the > > > > FUSE fs was unmounted: > > > > > > > > 19:41:46.513143 open("/dev/ttyS0", O_RDONLY|O_LARGEFILE) = 3 > > > > 19:41:46.513373 fstat64(3, {st_mode=S_IFCHR|0660, st_rdev=makedev(4, 64), ...}) = 0 > > > > 19:41:46.513552 read(3, "", 4096) = 0 > > > > 19:42:49.854367 close(3) = 0 > > > > 19:42:49.860663 close(1) = 0 > > > > 19:42:49.860793 exit_group(0) = ? > > > > > > > > Found this on x86 with kernels 2.6.16 and 2.6.17. > > > > > > > > Any ideas? > > > > > > Likely a userspace issue. Can you please attach a strace (strace -f > > > -p `pidof gphotofs`) to the gphotofs process just before doing the > > > unmount? > > > > Here it is together with the "cat" strace. cat receives EOF *after* > > fusermount has exited - if it matters. > > Yes, I think it matters. I think one of those USBDEVFS ioctls might > be responsible. These are probably invoked by the libgphoto2 cleanup > routines called when the filesystem exits. > > Can you verify with a non-FUSE application (gphoto2, gtkam) that the > same thing happens on exit? >
Tested both gphoto2 and gtkam without any problems. There is no impact on the serial lines.
NB: The *real* trouble I have is with ntpd and a reference clock attached to /dev/ttyS1. ntpd enters a busy loop reading ttyS1, stops working and eats up 100% CPU.
Thanks for your investigations. Any other idea?
-jo
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