Date: Mon, 13 Mar 2023 00:20:58 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270166 Bug ID: 270166 Summary: Upgrade to/new install of RELEASE 13.1 causes boot freeze (subr_clockcalib.c) Product: Base System Version: 13.1-RELEASE Hardware: amd64 OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: email@example.com Created attachment 240805 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=240805&action=edit Hack to correct described problem w/instrumentation Addition of and changes related to sys/kern/subr_clockcalib.c causes infinite loop / 1+ CPU 100% usage during boot. The termination condition of the loop is indeterminate. System details: Virtualized FreeBSD 13.x KVM guest on Fedora Linux 37, AMD Ryzen 9 3900XT 12-Core Processor. After bisection to commit baee6cc1814b8e851555d2caa6410eedcef2c6c8, added instrumentation printfs. This isolated the problem to the exit condition for clockcalib. The cpu() call never returned a value larger than 4294967295 when calibrating the LAPIC timer. The proposed solution (hack) captures the last clk() value and aborts the cpu_spinwait() loop if the current clk() and last value are the same. Because freq in this situation always ends up at 0, which causes a divide-by-zero error in the calling routine. A check for this condition with a return of 1 instead is included. I acknowledge there are cleaner ways to correct this problem, and I explored a kernel command-line option to fall-back to the previous behavior if desired. I have not figured how to accomplish this. -- You are receiving this mail because: You are the assignee for the bug.