I'm running RELENG_7 on a dual-core AMD64 system, with a kernel that is configured the same as GENERIC but with the WITNESS and INVARIANTS options added. Warnings of the form shown below are getting logged when I play multimedia files with mplayer. Is this anything to be concerned about? Should I open a PR? uma_zalloc_arg: zone "4096" with the following non-sleepable locks held: exclusive sleep mutex pcm0:play:dsp0.p0 (pcm play channel) r = 0 (0xffffff00033017c0) locked @ /usr/src/sys/modules/sound/sound/../../../dev/sound/pcm/vchan.c:448 KDB: stack backtrace: db_trace_self_wrapper() at db_trace_self_wrapper+0x2a witness_warn() at witness_warn+0x248 uma_zalloc_arg() at uma_zalloc_arg+0x33a malloc() at malloc+0x8a usbd_alloc_buffer() at usbd_alloc_buffer+0x8a uaudio_chan_alloc_buffers() at uaudio_chan_alloc_buffers+0x4d uaudio_trigger_output() at uaudio_trigger_output+0x3b ua_chan_trigger() at ua_chan_trigger+0x7a chn_trigger() at chn_trigger+0x117 chn_notify() at chn_notify+0xd5 vchan_trigger() at vchan_trigger+0x95 chn_trigger() at chn_trigger+0x117 chn_write() at chn_write+0x11b dsp_write() at dsp_write+0x2ef devfs_write_f() at devfs_write_f+0x9c dofilewrite() at dofilewrite+0x85 kern_writev() at kern_writev+0x4c write() at write+0x54 syscall() at syscall+0x1ce Xfast_syscall() at Xfast_syscall+0xab --- syscall (4, FreeBSD ELF64, write), rip = 0x80311fdcc, rsp = 0x7fffffffd6b8, rbp = 0x9485471f ---