Dear Maintainer,

I upgraded from jessie to stretch and find that the
"stable" system is a lot less stable than before, I'll
get to systemd eventually, but I had to deal with minor
issues like pulseaudio taking about 20 minutes to start,
and other problems reported in the logs. Systemctl reports other
failures I have to resolve, but pulseaudio is the start.

After searching for solutions on the internet, I
ran $ pulseaudio -vvvv  with this line in the output (among others)

core-util.c failed to acquire high-priority scheduling

The full message is this :
$ pulseaudio -vvvv
I: [pulseaudio] main.c: setrlimit(RLIMIT_NICE, (31, 31)) failed: Operation not permitted
I: [pulseaudio] main.c: setrlimit(RLIMIT_RTPRIO, (9, 9)) failed: Operation not permitted
D: [pulseaudio] core-rtclock.c: Timer slack is set to 50 us.
I: [pulseaudio] core-util.c: Failed to acquire high-priority scheduling: Input/output error
I: [pulseaudio] main.c: This is PulseAudio 10.0
D: [pulseaudio] main.c: Compilation host: x86_64-pc-linux-gnu
D: [pulseaudio] main.c: Compilation CFLAGS: -g -O2 -fdebug-prefix-map=/build/pulseaudio-ZMrhzG/pulseaudio-10.0=. -fstack-protector-strong -Wformat -Werror=format-security -Wall -W -Wextra -pipe -Wno-long-long -Wno-overlength-strings -Wunsafe-loop-optimizations -Wundef -Wformat=2 -Wlogical-op -Wsign-compare -Wformat-security -Wmissing-include-dirs -Wformat-nonliteral -Wpointer-arith -Winit-self -Wdeclaration-after-statement -Wfloat-equal -Wmissing-prototypes -Wredundant-decls -Wmissing-declarations -Wmissing-noreturn -Wshadow -Wendif-labels -Wcast-align -Wstrict-aliasing -Wwrite-strings -Wno-unused-parameter -ffast-math -fno-common -fdiagnostics-show-option -fdiagnostics-color=auto
D: [pulseaudio] main.c: Running on host: Linux x86_64 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2+deb9u5 (2017-09-19)
D: [pulseaudio] main.c: Found 4 CPUs.
I: [pulseaudio] main.c: Page size is 4096 bytes
D: [pulseaudio] main.c: Compiled with Valgrind support: no
D: [pulseaudio] main.c: Running in valgrind mode: no
D: [pulseaudio] main.c: Running in VM: no
D: [pulseaudio] main.c: Optimized build: yes
D: [pulseaudio] main.c: FASTPATH defined, only fast path asserts disabled.
I: [pulseaudio] main.c: Machine ID is .
I: [pulseaudio] main.c: Using runtime directory .
I: [pulseaudio] main.c: Using state directory .
I: [pulseaudio] main.c: Using modules directory /usr/lib/pulse-10.0/modules.
I: [pulseaudio] main.c: Running in system mode: no
E: [pulseaudio] pid.c: Daemon already running.
E: [pulseaudio] main.c: pa_pid_file_create() failed.

Taking advice, I added the following to /etc/security/limits.conf

@audio          -       rtprio          99
@audio          -       nice            -20
@audio          -       memlock         4000000

@pulse-rt - rtprio 99
@pulse-rt - nice        -15

I now get this after a reboot:
$ pulseaudio -vvvv
D: [pulseaudio] core-rtclock.c: Timer slack is set to 50 us.
D: [pulseaudio] core-util.c: setpriority() worked.
I: [pulseaudio] core-util.c: Successfully gained nice level -11.
I: [pulseaudio] main.c: This is PulseAudio 10.0
D: [pulseaudio] main.c: Compilation host: x86_64-pc-linux-gnu
D: [pulseaudio] main.c: Compilation CFLAGS: -g -O2 -fdebug-prefix-map=/build/pulseaudio-ZMrhzG/pulseaudio-10.0=. -fstack-protector-strong -Wformat -Werror=format-security -Wall -W -Wextra -pipe -Wno-long-long -Wno-overlength-strings -Wunsafe-loop-optimizations -Wundef -Wformat=2 -Wlogical-op -Wsign-compare -Wformat-security -Wmissing-include-dirs -Wformat-nonliteral -Wpointer-arith -Winit-self -Wdeclaration-after-statement -Wfloat-equal -Wmissing-prototypes -Wredundant-decls -Wmissing-declarations -Wmissing-noreturn -Wshadow -Wendif-labels -Wcast-align -Wstrict-aliasing -Wwrite-strings -Wno-unused-parameter -ffast-math -fno-common -fdiagnostics-show-option -fdiagnostics-color=auto
D: [pulseaudio] main.c: Running on host: Linux x86_64 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2+deb9u5 (2017-09-19)
D: [pulseaudio] main.c: Found 4 CPUs.
I: [pulseaudio] main.c: Page size is 4096 bytes
D: [pulseaudio] main.c: Compiled with Valgrind support: no
D: [pulseaudio] main.c: Running in valgrind mode: no
D: [pulseaudio] main.c: Running in VM: no
D: [pulseaudio] main.c: Optimized build: yes
D: [pulseaudio] main.c: FASTPATH defined, only fast path asserts disabled.
I: [pulseaudio] main.c: Machine ID is .
I: [pulseaudio] main.c: Session ID is 1.
I: [pulseaudio] main.c: Using runtime .
I: [pulseaudio] main.c: Using state directory .
I: [pulseaudio] main.c: Using modules directory /usr/lib/pulse-10.0/modules.
I: [pulseaudio] main.c: Running in system mode: no
E: [pulseaudio] pid.c: Daemon already running.
E: [pulseaudio] main.c: pa_pid_file_create() failed.

It looks like a bug in the source code in this line:
I: [pulseaudio] main.c: setrlimit(RLIMIT_NICE, (31, 31)) failed: Operation not permitted

I haven't checked to see if this is resolved in later versions of pulseaudio.
HopeThisHelps