umount() taking minutes for FUSE filesystems

[Ben RUBSON]

I managed to reproduce the issue.
unmount takes exactly 60 seconds, as if a timeout was running.

# procstat -kk $!
COMM     TDNAME KSTACK                       
printcap -      mi_switch+0xd2 sleepq_catch_signals+0xb7 sleepq_timedwait_sig+0x10 _sleep+0x26f fdisp_wait_answ+0x171 fuse_vfsop_unmount+0xf5 dounmount+0x9b6 sys_unmount+0x41b amd64_syscall+0x4ce Xfast_syscall+0xfb 

# uname -sr
FreeBSD 11.0-RELEASE-p9

Ben

> On 29 Aug 2017, at 17:02, Conrad Meyer <cem at freebsd.org> wrote:
> 
> Hey Nikolaus,
> 
> A first cut debug tactic might be running 'procstat -kk <pid of
> printcap process>' to see where it is spending time in the kernel.  I
> haven't had time to try and reproduce this myself, sorry.
> 
> Best,
> Conrad
> 
> On Tue, Aug 29, 2017 at 1:57 AM, Nikolaus Rath <Nikolaus at rath.org> wrote:
>> *ping*
>> 
>> Anyone able to help?
>> 
>> Thanks,
>> -Nikolaus
>> 
>> On Aug 24 2017, Nikolaus Rath <Nikolaus at rath.org> wrote:
>>> Hello,
>>> 
>>> It seems that in some situations, the unmount() system call takes
>>> minutes to unmount fuse filesystems. To reproduce, download a Git
>>> snapshot of libfuse 3 from https://github.com/libfuse/libfuse and do:
>>> 
>>> $ md build; cd build
>>> $ meson ..
>>> $ mesonconf -D buildtype=debug # optional
>>> $ ninja
>>> 
>>> Then execute examples/printcap. This will take very long, and all the
>>> time is spent in the unmount(mountpoint, MNT_FORCE) call in
>>> mount_bsd.c:fuse_kern_unmount().
>>> 
>>> Does anyone have an idea what might be causing this and how to fix it?
>>> 
>>> My hunch is that it has something to do with libfuse no longer
>>> responding to requests at this point. But I'm at my wits end as to why
>>> and what to do about it....
>>> 
>>> Best,
>>> -Nikolaus
>>> 
>>> --
>>> GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F
>>> 
>>>             »Time flies like an arrow, fruit flies like a Banana.«
>>> _______________________________________________
>>> freebsd-fs at freebsd.org mailing list
>>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
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>> 
>> 
>> --
>> GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F
>> 
>>             »Time flies like an arrow, fruit flies like a Banana.«
>> _______________________________________________
>> freebsd-fs at freebsd.org mailing list
>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org"
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