Date: Thu, 21 Jun 2001 08:55:21 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: John Baldwin <jhb@FreeBSD.ORG>, Andrew Gallatin <gallatin@cs.duke.edu> Cc: <alpha@FreeBSD.ORG> Subject: more panics, with some traceback info.... Message-ID: <20010621081950.Q18589-100000@wonky.feral.com>
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panic: blockable sleep lock (sleep mutex) Giant @ ../../vm/vm_fault.c:213
cpuid = 0; panic
db> t
Debugger() at Debugger+0x34
panic() at panic+0x178
witness_lock() at witness_lock+0x240
vm_fault() at vm_fault+0x108
trap() at trap+0xf78
XentMM() at XentMM+0x2c
--- memory management fault (from ipl 7) ---
hardclock() at hardclock+0x308
handleclock() at handleclock+0x22c
alpha_clock_interrupt() at alpha_clock_interrupt+0x68
interrupt() at interrupt+0xb8
XentInt() at XentInt+0x28
--- interrupt (from ipl 0) ---
witness_unlock() at witness_unlock+0x50
zalloc() at zalloc+0x28c
get_pv_entry() at get_pv_entry+0x70
pmap_insert_entry() at pmap_insert_entry+0x34
pmap_enter_quick() at pmap_enter_quick+0x214
pmap_object_init_pt() at pmap_object_init_pt+0x1b8
vm_map_insert() at vm_map_insert+0x37c
elf_load_section() at elf_load_section+0x33c
exec_elf_imgact() at exec_elf_imgact+0x528
execve() at execve+0x274
syscall() at syscall+0x708
XentSys() at XentSys+0x64
--- syscall (59, FreeBSD ELF, execve) ---
--- user mode ---
db> show locks
exclusive (sleep mutex) zone (0xfffffc000083d5c0) locked @
../../vm/vm_zone.c:373
exclusive (sleep mutex) vm (0xfffffc000084b180) locked @
../../kern/imgact_elf.c:236
exclusive (sleep mutex) Giant (0xfffffc000084be18) locked @
../../vm/vm_fault.c:213
exclusive (spin mutex) callout (0xfffffc0000845238) locked @
../../kern/kern_clock.c:213
A minor amount of sleuthing yields:
if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) {
as nearest the likely faulting line. A little sleuthing around about the value
of ticks && callwheelmask led me to believe that I should check the contents
of callwheel... so, callwheelmask was 4095, and masking that with ticks, I
went to check into that offset via DDB, and the system froze- I probably got
the offset wrong.
The assembler lines are:
hardclock+0x2e0: addq t0,#0x1,t0
hardclock+0x2e4: stl t0,0(t1)
ticks++; /* leaving ticks in t0 */
hardclock+0x2e8: ldq t1,0xffffffffffffbe68(gp)
hardclock+0x2ec: ldl t1,0(t1)
hardclock+0x2f0: and t0,t1,t0
Fetch callwheelmask, mask against ticks
hardclock+0x2f4: addl t0,zero,t0
hardclock+0x2f8: ldq t1,0xffffffffffff89e8(gp)
hardclock+0x2fc: ldq t1,0(t1)
Fetch callwheel (?)
hardclock+0x300: sll t0,#0x4,t0
Turn masked ticks into an index
hardclock+0x304: addq t0,t1,t0
Form address to fetch
hardclock+0x308: ldq t0,0(t0)
Fetch callwheel[ticks & callwheelmask]
-matt
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