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Date:      Thu, 11 Jun 2026 13:17:34 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 296001] hwpmc: panic: [amd,526] pmc6,cpu15: Starting active PMC "K8-L3-0"
Message-ID:  <bug-296001-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=296001

            Bug ID: 296001
           Summary: hwpmc: panic: [amd,526] pmc6,cpu15: Starting active
                    PMC "K8-L3-0"
           Product: Base System
           Version: 16.0-CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: asomers@FreeBSD.org

I get this cryptic panic whenever I try to start hwpmc to measure l3_misses on
my AMD Ryzen system.  I can instantly reproduce it.

Environment
===========
FreeBSD 16.0-CURRENT at c289291a673 (main branch as of 9-June-2026)
AMD Ryzen 9 5950X 16-Core Processor

Steps to Reproduce
==================
sudo kldload hwpmc
sudo -E pmcstat -P l3_misses -d -O /tmp/cache_misses.log cargo build

Stack Trace
===========

#0  __curthread ()
    at
/usr/home/somers/src/freebsd.org/src/main/sys/amd64/include/pcpu_aux.h:57
#1  doadump (textdump=textdump@entry=0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_shutdown.c:399
#2  0xffffffff804c665a in db_dump (dummy=<optimized out>,
    dummy2=<optimized out>, dummy3=<optimized out>, dummy4=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/ddb/db_command.c:596
#3  0xffffffff804c650a in db_command (last_cmdp=<optimized out>,
    cmd_table=<optimized out>, dopager=true)
    at /usr/home/somers/src/freebsd.org/src/main/sys/ddb/db_command.c:508
#4  0xffffffff804c612d in db_command_loop ()
    at /usr/home/somers/src/freebsd.org/src/main/sys/ddb/db_command.c:555
#5  0xffffffff804c9d60 in db_trap (type=<optimized out>, code=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/ddb/db_main.c:267
#6  0xffffffff80c5ba2f in kdb_trap (type=type@entry=3, code=code@entry=0,
    tf=tf@entry=0xfffffe0165dcc6b0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/subr_kdb.c:790
#7  0xffffffff8118e3c8 in trap (frame=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/amd64/amd64/trap.c:697
#8  <signal handler called>
#9  kdb_enter (why=<optimized out>, msg=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/subr_kdb.c:556
#10 0xffffffff80c05be9 in vpanic (fmt=<optimized out>,
    ap=ap@entry=0xfffffe0165dcc8e0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_shutdown.c:962
#11 0xffffffff80c05a63 in panic (
    fmt=0xffffffff81da2270 <cnputs_mtx> "8\020(\201\377\377\377\377")
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_shutdown.c:887
#12 0xffffffff83866802 in amd_start_pmc (cpu=15, ri=6, pm=0xfffff8000d3da300)
    at /usr/home/somers/src/freebsd.org/src/main/sys/dev/hwpmc/hwpmc_amd.c:525
#13 0xffffffff8385c059 in pmc_process_csw_in (td=0xfffff80031581780)
    at /usr/home/somers/src/freebsd.org/src/main/sys/dev/hwpmc/hwpmc_mod.c:1585
#14 pmc_hook_handler (td=0xfffff80031581780, function=<optimized out>,
    arg=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/dev/hwpmc/hwpmc_mod.c:2171
#15 0xffffffff80c3e039 in sched_ule_sswitch (td=0xfffff80031581780,
    flags=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/sched_ule.c:2415
#16 0xffffffff80c12f82 in mi_switch (flags=flags@entry=259)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_synch.c:526
#17 0xffffffff80c6f049 in sleepq_switch (wchan=wchan@entry=0xfffff80034b4e780,
    pri=pri@entry=0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/subr_sleepqueue.c:608
#18 0xffffffff80c6f426 in sleepq_catch_signals (wchan=0xfffff80034b4e780,
    pri=0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/subr_sleepqueue.c:523
#19 0xffffffff80c6f179 in sleepq_wait_sig (
    wchan=0xffffffff81da2270 <cnputs_mtx>, pri=1708967472)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/subr_sleepqueue.c:671
#20 0xffffffff80c12497 in _sleep (ident=ident@entry=0xfffff80034b4e780,
    lock=lock@entry=0xffffffff81de9740 <umtxq_chains+15840>,
    priority=priority@entry=768,
    wmesg=wmesg@entry=0xffffffff8131b9be "urdlck", sbt=sbt@entry=0,
    pr=pr@entry=0, flags=0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_synch.c:220
#21 0xffffffff80c28952 in umtxq_sleep (uq=uq@entry=0xfffff80034b4e780,
    wmesg=0xffffffff8131b9be "urdlck", timo=timo@entry=0x0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_umtx.c:843
#22 0xffffffff80c3288a in do_rw_rdlock (td=0xfffff80031581780,
    rwlock=0x33d86e023b00, fflag=<optimized out>, timeout=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_umtx.c:3217
#23 0xffffffff80c2ae79 in kern__umtx_op (td=0xffffffff81da2270 <cnputs_mtx>,
    obj=<optimized out>, val=18, uaddr1=0x0, uaddr2=<optimized out>,
    ops=0xffffffff813b3e80, op=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_umtx.c:4994
#24 sys__umtx_op (td=0xffffffff81da2270 <cnputs_mtx>, uap=<optimized out>)
    at /usr/home/somers/src/freebsd.org/src/main/sys/kern/kern_umtx.c:5019
#25 0xffffffff8118f269 in syscallenter (td=0xfffff80031581780)
    at
/usr/home/somers/src/freebsd.org/src/main/sys/amd64/amd64/../../kern/subr_syscall.c:193
#26 amd64_syscall (td=0xfffff80031581780, traced=0)
    at /usr/home/somers/src/freebsd.org/src/main/sys/amd64/amd64/trap.c:1257

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