Not enough information. I recommend starting jackd with strace

This code tries to call sched_setscheduler() with SCHED_FIFO. My bet is that your "almost vanilla kernel" fails to fulfil this request, but strace will tell you for sure.

The question is why said call should fail. The only thing that comes to my mind are CGROUPS. Maybe your old kernel comes without, the new kernel supports them and the configuration is set in a way that disables SCHED_FIFO by default.

On Sat, Apr 4, 2015 at 8:13 PM, Adrian Knoth &lt;adi(a)drcomp.erfurt.thur.de <mailto:adi@drcomp.erfurt.thur.de>> wrote: Not enough information. I recommend starting jackd with strace Done - apologies for the delay. Strace output available[1], but the most interesting part copied here: sched_get_priority_min(SCHED_FIFO) = 1 sched_setscheduler(0, SCHED_FIFO, { 1 }) = -1 EPERM (Operation not permitted) write(2, "\nJACK is running in realtime mod"..., 87 JACK is running in realtime mode, but you are not allowed to use realtime scheduling. ) = 87 This code tries to call sched_setscheduler() with SCHED_FIFO. My bet is that your "almost vanilla kernel" fails to fulfil this request, but strace will tell you for sure. By "almost vanilla" I meant the Arch linux packaged version - I didn't change the config myself (and Arch aims to be true to vanilla). A very accurace prediction though - indeed sched_setscheduler() is causing a return of -1. This is running as root though - so something is wrong here. The question is why said call should fail. The only thing that comes to my mind are CGROUPS. Maybe your old kernel comes without, the new kernel supports them and the configuration is set in a way that disables SCHED_FIFO by default. Perhaps - I'm not experienced with cgroups or such, if anybody has any test ideas for me I'll try them out? Cheers, -Harry [1] http://openavproductions.com/tmp/straceJackd.txt _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev(a)lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev

On Sat, Jun 06, 2015 at 03:35:16PM +0100, Harry van Haaren wrote: No tested but perhaps the follow lines in __sched_setscheduler (linux-3.19.8/kernel/sched/core.c) are relevant: #ifdef CONFIG_RT_GROUP_SCHED /* * Do not allow realtime tasks into groups that have no runtime * assigned. */ if (rt_bandwidth_enabled() && rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0 && !task_group_is_autogroup(task_group(p))) { task_rq_unlock(rq, p, &flags); return -EPERM; } #endif #ifdef CONFIG_SMP if (dl_bandwidth_enabled() && dl_policy(policy)) { cpumask_t *span = rq->rd->span; /* * Don't allow tasks with an affinity mask smaller than * the entire root_domain to become SCHED_DEADLINE. We * will also fail if there's no bandwidth available. */ if (!cpumask_subset(span, &p->cpus_allowed) || rq->rd->dl_bw.bw == 0) { task_rq_unlock(rq, p, &flags); return -EPERM; } } #endif However I'm using 3.10 compiled without CONFIG_RT_GROUP_SCHED and the second `#ifdef' (CONFIG_SMP) is not present in the source code. Hypothesis: the second condition fails => disable the bandwidth management logic (the default is 950000): echo -1 > /proc/sys/kernel/sched_rt_runtime_us More info about sched_rt_runtime_us: scheduler/sched-rt-group.txt: "2.1 System wide settings" scheduler/sched-deadline.txt: "4.1 System wide settings" If it continues to fail and your kernel is compiled with CONFIG_RT_GROUP_SCHED, you could recompile it without this configuration option (if you don't use realtime group scheduling). Oh, if it continues to fail, see the other branches with `return -EPERM' in __sched_setscheduler. _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev(a)lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev