System Info

• Steam client version (build number or date): Dec 12 2019, at 22:37:09
• Distribution (e.g. Ubuntu): Ubuntu 64 bit 18.04.3 (with HWE, kernel 5.0.0-37-generic)
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

After 1 minute running, the steam client uses 100% CPU until closing it down.
I can clearly see from htop that the CPU time is 60% user and 40% system.

That's why I've attached a strace of the steam process.

Please find also a strace at startup, when the CPU is only used around 10% or less.
At the end of this trace the infinite loop starts.

Looking at the traces, seems like when it goes into an infinite loop there are calls to futex and other OS APIs which are not present in the sane strace:

recvmsg(27, {msg_namelen=0}, 0)         = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(27, {msg_namelen=0}, 0)         = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(27, {msg_namelen=0}, 0)         = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=27, events=POLLIN}, {fd=28, events=POLLIN}], 2, 0) = 0 (Timeout)
read(5, "", 1023)                       = 0
semop(524288, [{0, -1, IPC_NOWAIT}], 1) = -1 EAGAIN (Resource temporarily unavailable)
nanosleep({tv_sec=0, tv_nsec=0}, NULL)  = 0
waitpid(-1, NULL, WNOHANG)              = 0
write(41, "\1\0\0\0\0\0\0\0", 8)        = 8
futex(0x58c1e6b0, FUTEX_WAIT_PRIVATE, 0, {tv_sec=89, tv_nsec=999999821}) = -1 EAGAIN (Resource temporarily unavailable)
futex(0x58c1e66c, FUTEX_WAKE_PRIVATE, 1) = 0
write(41, "\1\0\0\0\0\0\0\0", 8)        = 8
futex(0x58c1e6ac, FUTEX_WAIT_PRIVATE, 0, {tv_sec=89, tv_nsec=999999923}) = 0
futex(0x58c1e66c, FUTEX_WAKE_PRIVATE, 1) = 0
waitpid(-1, NULL, WNOHANG)              = 0
clock_gettime(CLOCK_MONOTONIC_RAW, {tv_sec=2944, tv_nsec=154365720}) = 0
recvmsg(34, {msg_namelen=0}, 0)         = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=34, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
poll([{fd=114, events=POLLIN}], 1, 0)   = 0 (Timeout)
poll([{fd=22, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)

Steps for reproducing this issue:

1. Execute Steam
2. Go to any page of any game of your library, or wait 1 minute in your main Steam page
3. Wait ~30 seconds (happens with both IPv6 enabled or disabled)