> > > In which situation? > > > > I was testing something that listens for alsa events and for that I ran > > a continuous loop that did: > > > > while true > > do > > aconnect 128:1 14:0 > > aconnect -d 128:1 14:0 > > aconnect -d 128:2 128:1 > > aconnect 128:2 128:1 > > done > > > > I ran 5 instances in parallel. > > > > 14 is midi through > > 128 is rtpmidi > > So rtpmidi process keeps running during the loop, that is, it's only > about connection and disconnection, right? > Also, you're listening to an event during that -- but how? I tried it again but with a simpler setup: I've got these devices: root@lappiemctopface:~# aplaymidi -l Port Client name Port name 14:0 Midi Through Midi Through Port-0 130:0 FLUID Synth (17032) Synth input port (17032:0) 131:0 VMPK Input in root@lappiemctopface:~# arecordmidi -l Port Client name Port name 14:0 Midi Through Midi Through Port-0 132:0 VMPK Output out I run this in 3x parallel: while true do aconnect 132:0 130:0 aconnect -d 132:0 130:0 done and then in less than a minute I get a backtrace. [ma aug 2 11:05:13 2021] Call Trace: [ma aug 2 11:05:13 2021] ? snd_seq_deliver_event+0x38/0x90 [snd_seq] [ma aug 2 11:05:13 2021] ? snd_seq_kernel_client_dispatch+0x72/0x90 [snd_seq] [ma aug 2 11:05:13 2021] kfree+0x3bc/0x3e0 [ma aug 2 11:05:13 2021] ? snd_seq_port_disconnect+0x10c/0x140 [snd_seq] [ma aug 2 11:05:13 2021] snd_seq_port_disconnect+0x10c/0x140 [snd_seq] [ma aug 2 11:05:13 2021] snd_seq_ioctl_unsubscribe_port+0xb9/0x180 [snd_seq] [ma aug 2 11:05:13 2021] ? snd_seq_port_get_subscription+0xbb/0xd0 [snd_seq] [ma aug 2 11:05:13 2021] ? __check_object_size.part.0+0x3a/0x150 [ma aug 2 11:05:13 2021] snd_seq_ioctl+0xe8/0x1b0 [snd_seq] [ma aug 2 11:05:13 2021] __x64_sys_ioctl+0x91/0xc0 [ma aug 2 11:05:13 2021] do_syscall_64+0x38/0x90 [ma aug 2 11:05:13 2021] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Using: fluidsynth 2.1.7-1 vmpk 0.7.2-1build1 On: 5.11.0-25-generic (ubuntu) on 2 cores, 2 threads/core cpu (64b).