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Date:      Sat, 6 Jan 2007 01:34:02 +0100
From:      Frode Nordahl <frode@nordahl.net>
To:        freebsd-stable@freebsd.org
Subject:   Livelock in 6.2-RC1
Message-ID:  <0491A255-404B-4802-851C-43F4691C19E2@nordahl.net>

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Hello colleagues,

I am experiencing a rare livelock on four of my backend mail servers  
running 6.1-STABLE, 6.2-BETA2 and 6.2-RC1. They are running OpenLDAP  
slapd, postfix and UW-IMAPD.

The servers can run for months without any problem, but nevertheless  
I have experienced this problem on multiple versions and different  
hardware configurations about 5 times since september / october 2006.

Server is responding to pings, but all other activity halts.

On one occasion when one of the servers displayed this behaviour it  
managed to recover from the situation by itself after being gone for  
20-30 minutes.

Typical hardware configuration:
CPU  2x Xeon 3.06GHz or 1x Core2Duo 2.00GHz (SMP)
RAM  4 GB RAM
DISK Intel SRCU42X (amr) or Dell PERC 5/i (mfi)

Kernel config:
include GENERIC
options         KDB                     # Enable kernel debugger  
support.
options         BREAK_TO_DEBUGGER
options         DDB                     # Support DDB.
options         GDB                     # Support remote GDB.
options         QUOTA
options         SMP

On the last crash i collected the following info from DDB:
db> tr
Tracing pid 11 tid 100005 td 0xc8f90780
kdb_enter(c092f08b) at kdb_enter+0x2b
siointr1(c9120800) at siointr1+0xce
siointr(c9120800) at siointr+0x5e
intr_execute_handlers(c8f864c8,e7b14c94,4,e7b14cd8,c0889503,...) at  
intr_execute_handlers+0xe1
lapic_handle_intr(3d) at lapic_handle_intr+0x2e
Xapic_isr1() at Xapic_isr1+0x33
--- interrupt, eip = 0xc0b5b0e5, esp = 0xe7b14cd8, ebp = 0xe7b14cd8 ---
acpi_cpu_c1(0,0,e7b14cf8,c8f90780,1,...) at acpi_cpu_c1+0x5
acpi_cpu_idle(e7b14d10,c066a779,c8f8fa78,c066a6e4,e7b14d24,...) at  
acpi_cpu_idle+0x152
cpu_idle(c8f8fa78,c066a6e4,e7b14d24,c066a465,0,...) at cpu_idle+0x28
idle_proc(0,e7b14d38) at idle_proc+0x95
fork_exit(c066a6e4,0,e7b14d38) at fork_exit+0x71
fork_trampoline() at fork_trampoline+0x8
--- trap 0x1, eip = 0, esp = 0xe7b14d6c, ebp = 0 ---


db> show lockedbufs
buf at 0xdd08cbd0
b_flags = 0x20000000<vmio>
b_error = 0, b_bufsize = 16384, b_bcount = 16384, b_resid = 0
b_bufobj = (0xc937ed80), b_data = 0xdea14000, b_blkno = 14386688
b_npages = 4, pages(OBJ, IDX, PA): (0xc1045210, 0x1b70c0, 0xdbe35000), 
(0xc1045210, 0x1b70c1, 0xc17d6000),(0xc1045210, 0x1b70c2, 0x582d7000), 
(0xc1045210, 0x1b70c3, 0x84498000)

I have a crashdump or two available for further investigation.

--
Frode Nordahl






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