Date: Mon, 16 Feb 2009 21:38:17 GMT From: Jari Kirma <kirma.at.cs.hut.fi@FreeBSD.org> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/131753: kernel panic in hfsc_dequeue Message-ID: <200902162138.n1GLcHsb069499@www.freebsd.org> Resent-Message-ID: <200902162140.n1GLe233082835@freefall.freebsd.org>
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>Number: 131753
>Category: kern
>Synopsis: kernel panic in hfsc_dequeue
>Confidential: no
>Severity: serious
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Feb 16 21:40:02 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator: Jari Kirma
>Release: 7.1-STABLE
>Organization:
Helsinki University of Technology
>Environment:
FreeBSD xxx 7.1-STABLE FreeBSD 7.1-STABLE #17: Sat Jan 31 12:09:54 EET 2009 xxx@xxx:/usr/obj/usr/src/sys/XXX i386
>Description:
System (four-core Intel Q6600 with SMP kernel) crashes under load (although relatively light load, thanks to only 2 Mbit outbound link) of roughty hundred TCP connections somewhat reproducibly when HFSC ALTQ traffic scheduling is used.
Only information seen about this is the dmesg message:
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address = 0x4
fault code = supervisor read, page not present
instruction pointer = 0x20:0xc04641e7
stack pointer = 0x28:0xe719ca68
frame pointer = 0x28:0xe719caac
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
current process = 15 (swi4: clock sio)
trap number = 12
panic: page fault
Where the instruction pointer points to inlined code inside hfsc_dequeue:
(gdb) l *(0xc04641e7)
0xc04641e7 is in hfsc_dequeue (altq_classq.h:113).
108 struct mbuf *m, *m0;
109
110 if ((m = qtail(q)) == NULL)
111 return (NULL);
112 if ((m0 = m->m_nextpkt) != m)
113 m->m_nextpkt = m0->m_nextpkt;
114 else
115 qtail(q) = NULL;
116 qlen(q)--;
117 m0->m_nextpkt = NULL;
Could it be just a simple locking issue in the linked list?
>How-To-Repeat:
Exact conditions are not known, but running lots of outbound TCP traffic over HFSC connection on a SMP system might trigger it.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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