[LAU] JACK hangs on openSUSE Tumbleweed

[Jörn Nettingsmeier]

Hi *!


I've come across a mysterious problem - since a few days ago (openSUSE 
Tumbleweed is a rolling release), JACK hangs during startup. If you 
start it with QJackCtl, it will kill it after a while, but if you start 
it from the console and strace it, you can see it hangs waiting for a futex:
[...]
sched_get_priority_min(SCHED_FIFO)      = 1
sched_get_priority_max(SCHED_FIFO)      = 99
mmap(NULL, 8392704, PROT_READ|PROT_WRITE, 
MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f9e76cfe000
mprotect(0x7f9e76cfe000, 4096, PROT_NONE) = 0
clone(child_stack=0x7f9e774fdfb0, 
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, 
parent_tidptr=0x7f9e774fe9d0, tls=0x7f9e774fe700, 
child_tidptr=0x7f9e774fe9d0) = 4627
sched_setscheduler(4627, SCHED_FIFO, { 1 }) = 0
futex(0x7f9e774fed18, FUTEX_WAKE_PRIVATE, 1) = 1
munmap(0x7f9e7ba87000, 227354)          = 0
futex(0x7f9e776ff078, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x7f9e774fe9d0, FUTEX_WAIT, 4627, NULL) = ? ERESTARTSYS (To be 
restarted if SA_RESTART is set)
--- SIGWINCH {si_signo=SIGWINCH, si_code=SI_KERNEL} ---
futex(0x7f9e774fe9d0, FUTEX_WAIT, 4627, NULL

and hangs forever after.
It seems to be after acquiring SCHED_FIFO, but just to be sure I 
verified that I'm still in group audio, and we still have
@audio          -       rtprio          95
@audio          -       memlock         3000000
in /etc/security/limits.conf.

The problem started at the same time kernel 3.19.3 came out for 
Tumbleweed, but downgrading to older kernels in the 3.19 series or as 
far back as 3.17 doesn't restore jack functionality. So it must be 
something in userspace.

Other people have seen this [1] and solved it with the nuclear option, 
i.e. downgrading to 13.2, which means a massive userspace rollback.

I wonder if someone could offer some advice as to where else to look...

I did the usual checkup regarding double installs, and I'm positive my 
jackd installation is clean. The guys in [1] have used the package, and 
I've tried both the package and a clean jack1 and jack2 build from 
scratch, with all other libs cleared by hand and ldd relations checked.


Any inspiration welcome,


Jörn




[1] 
https://forums.opensuse.org/showthread.php/506613-after-update-Tumbleweed-I-can-t-start-Jackd-Jack-Connection-Kit 
(not a very insightful discussion)



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Jörn Nettingsmeier
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