Re: kern/42455: tstile hang with nfs

["Christoph Egger" <Christoph_Egger%gmx.de@localhost>]

The following reply was made to PR kern/42455; it has been noted by GNATS.

From: "Christoph Egger" <Christoph_Egger%gmx.de@localhost>
To: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%netbsd.org@localhost, 
gnats-admin%netbsd.org@localhost,
 kern-bug-people%netbsd.org@localhost
Cc: 
Subject: Re: kern/42455: tstile hang with nfs
Date: Wed, 20 Oct 2010 15:10:57 +0200

 I added debug printf's right before every 'goto nfsmout'
 in the macros.
 
 When the bug happened again I saw none of the debug printf's.
 
 I also printed the 'mb' address and in ddb 'show mbuf' says:
 
 db> show mbuf 0xffffa00001170400
 MBUF 0xffffa00001170400
   data=0xffffa000011a2802, len=2046, type=1, flags=0x0x9000003<EXT,PKTHDR,
 EXT_CLUSTER,EXT_RW>
   owner=0x0, next=0x0, nextpkt=0x0
   leadingspace=2, trailingspace=0, readonly=0
   pktlen=2046, rcvif=0x0, csum_flags=0x0x0, csum_data=0x0, segsz=402653184
   ext_refcnt=1, ext_buf=0xffffa000011a2800, ext_size=2048, ext_free=0x0,
 ext_arg=0xffffa0002320d3d0
 
 next=0x0 => mb is not a chained mbuf.
 
 nwc.mbuf_count is initialized with 1
 and nwc.mbuf_count is decreased by one right before it enters
 the while loop with 'cv_wait' so nwc.mbuf_count must have
 been 2 before it entered the loop.
 
 There is only one way to increase nwc.mbuf_count: it must run
 the path where MEXTADD() is used which chains an mbuf to 'mb'.
 
 Christoph